கவனிக்க: இந்த மின்னூலைத் தனிப்பட்ட வாசிப்பு, உசாத்துணைத் தேவைகளுக்கு மட்டுமே பயன்படுத்தலாம். வேறு பயன்பாடுகளுக்கு ஆசிரியரின்/பதிப்புரிமையாளரின் அனுமதி பெறப்பட வேண்டும்.
இது கூகிள் எழுத்துணரியால் தானியக்கமாக உருவாக்கப்பட்ட கோப்பு. இந்த மின்னூல் மெய்ப்புப் பார்க்கப்படவில்லை.
இந்தப் படைப்பின் நூலகப் பக்கத்தினை பார்வையிட பின்வரும் இணைப்புக்குச் செல்லவும்: The Journal of the National Agricultural Society of Ceylon 1965.06

Page 1
THE J ーリー 。 OF
NATIONAL A
SOCIETY O
Vol. 2 JUNE
Ο ΟΝΤ
SANTHIERASEGARAM
. N. HASSELO
SIKUT RAJA PATHY
E A WIKRAMANAYAKE
. VISSER
CAESAR
HERAT NO
. C. BANSIL
THAMBYAHIPILLAY
. . T. SEN EVI RATNE
Published by the National A Price per singl
 

露R GEもリリYAH"リ*了
OURNAL #-
THE GRICULTURAL
DF CEYLON
1965 No. 1
E N T S
Inter cropping with Coconuts.
Estimations of losses and erodibility of tea soils during the replanting period.
The small tractor. (Its uses and limitations in the mechanisation of Ceylon's agriculture).
Tolerance to bacterial wilt (Pseudomonas solanacearum E. F. S.) and yield of potato varieties in the up-country of
Ceylon.
The effect of water temperature on Rice (Oryza sativa L.) and its influence on cold tolerance & disease resistance.
Peasant agriculture in Ceylon.
Dry zone climatology.
Phosphorus nutrition of the Rice plant.
gricultural Society of Ceylon. : copy Rs. 3-00
...ള്ള

Page 2
The National Agricultural Society of Ceylon was formed in July 1962, by
University graduates in the Agricultural
Sciences, to promote the advancement of Agriculture in respect of Policy, Production, Development and Education. The Journal of the Society vill be
published annually or more frequently. The Journal is intended to cover all
phases of Agriculture and Horticulture.
Articles for publication, as well as editorial
communications should be addressed to:
Dr. R. R. APPADURAI,
Department of Agriculture,
University of Ceylon,
Perαdenίγα.

DR. GEORGE THAMBY AHPILLAY
THE JOURNAL OF THE
NATIONAL AGRICULTURAL
SOCIETY OF CEYLON
@
Vol. 2 JUNIE 1965 No.
Editor
R. R. APPADURA
Printed at Lankapradipa Printing Works, Kandy, for the National Agricultural Society of Ceylon.

Page 3
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VISSER
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Page
Inter cropping with Coconuts. 2
Estimations of losses and erodibility of tea soils during the replanting period. 13
The small tractor. (Its uses and limitations in the mechanisation of Ceylon's agriculture). 22
Tolerance to bacterial wilt (Pseudomonas solanacearum E. F. S.) and yield of potato varieties in the up-country of
Ceylon. 33
The effect of water temperature on Rice (Oryza sativa L.) and its influence on cold tolerance & disease resistance. 65
Peasant agriculture in Ceylon. 74
Dry zone climatology. 88
Phosphorus nutrition of the Rice plant. 13

Page 7
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To meet the increased cost of replanting, the subsidies payable under the Replanting Scheme have been increased as follows :-
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RUBBER CONTROLLER, RUBBER CONTROL DEPARTMENT, P. O. Box 184, COLOMBO.

Page 10
CONTRIBUTORS.
K. SANTHIRASEGARAM, B. Sc. (Hons.) (Ceylon); Ph. D. (Adelaide), Agrostologist, Coconut Research Institute.
H. N. HASSELO, M. Sc; Ph.D. (Agric. Univ. Wageningen); Dipl. Aerial Survey (I. T. C. Delft.): Chief Agronomist,
Tea Research Institute.
M. SIKURAJAPATHY, B. Sc. Agric. (Ceylon) Technical Assistant, Agronomy Division, Tea Research Institute.
V. E. A. WIKRAMANAYAKE, B. Sc. Agric. (Bombay); M. S. A. (Toronto); A. M. I. Agric. E., Lecturer in Agricultural Engineering, University of Ceylon.
T. WISSER, Dr. Ir. (Wageningen); Formerly of the Tea
Research Institute.
K. CEASAR, Dr. Agric. (Hohenheim); Diploma Gaertner,
Potato Specialist, Department of Agriculture.
W. HERAT, B. Sc. Agric; M. Sc. (British Columbia) Asst
Lecturer in Agriculture, University of Ceylon.
P. C. BANSIL, M. A; Ph. D, F. A. O., Consultant in Agricultural Economics, Dept. of National Planning.
G. THAMBYAHPILLAI, M. A. (Calif.); Ph. D. (Cantab.); F.R. Met. S., Senior Lecturer in Geography, University of Ceylon.
S. T. SENEWIRATNE, B. Sc. Agric. (Ceylon); M. Sc., Ph. D. (Calif.); Professor and Head of the Department of Agriculture, University of Ceylon.

INTER CROPPING WITH COCONUTS
(Review of biological principles involved)
K. SANTHIRASEGARAM
I. INTRODUCTION
INTERCROPPING is practised in various forms in nearly
all parts of the world (16). It is common practice in the temperate countries to sow a pasture mixture with the last cereal crop in the rotation. In the tropics a species of plant is grown with a crop either to provide shade as in cocoa, or for support as in pepper cultivation.
In Ceylon a deliberate attempt is being made to explore the possibilities of raising a subsidiary crop under coconuts. The practice however is not new, as considerable amounts of vegetables, fruits and a primitive form of dairy and meat production do exist. The reasons for this renewed interest are the need to produce more food and also to increase the income per acre of the coconut lands. In a country like Ceylon with limited land, intensification of agriculture is inevitable and coconut is probably the only crop under which the intensity of light is sufficient for satisfactory growth of another crop. In fact weed growth beneath a coconut canopy is a problem; species such as Imperata cylindrica (l4) Eupatoram odoratam (15) and more recently Pennisetum sp. have been a menace in coconut estates causing considerable loss of yield of nuts and inconvenience in the normal activities of an estate. Intercropping is an attempt to replace the normal weed population with useful and productive species.
The Coconut Research Institute has carried out considerable pioneer work in this field. Pieris (II) has studied the possibilities of growing bananas Musa paradasia under coconuts. Salgado (12 & 13) has recorded the effect of fodder grass Pennisetum perpureum and leguminous cover
2

Page 11
crops on the yield of coconuts. More recently Santhrasegaram (17) recorded the effects of monospecific grass swards on the yield of coconuts. In view of the fact that a vast majority of the cattle population of the island exists in the coconut growing areas and with the pressing needs to increase the production of meat and milk for local consumption, the Coconut Research Institute had, in 1952. appointed an officer to study the possibilities of animal husbandry under coconuts, and in 1955, with the aid of a Colombo Plan expert inaugurated the division of Agronomy; and later in 1958 changed the division more specifically to the study of various aspects of pasture production under coconuts and designated it as the division of Agrostology.
II. ECOLOGY OF INTERCROPPING
As already pointed out weed growth when unchecked causes loss of yield of coconuts. This is because for the excess growth the weed plants utilise a part of the environmental factors otherwise available for the coconut palms. This phenomenon is called competition. Plants growing together compete for the essential growth factors such as soil moisture, nutrients, light and carbon dioxide. Competition is a purely physical process and commences as soon as any one or more of these essential factors are in supply below the requirements of the association. (4)
Thus when another crop is planted with coconut and if any one or more of the essential factors are in short supply, competition for these factors will be operative. This competition between two species of plants is called interspecific competition. The competition within the plants of a species is called intraspecific competition.
Numerous possibilities would occur when various crops are mixed with coconut. In the first instance the associated crop will have some effect on the yield of coconuts and conversely the coconut will affect the yield of the associated crop.
In studying interspecific competition it is necessary to take into consideration density of the species in pure and mixed cultures. In the first instance the density of coconuts in any environment is assumed to be the optimum density;
3
به اهل
;((.|\
 

and the associate is mixed at its own assumed optimum density in pure culture. Under such simple addition of the two pure cultures, the yield per plant and therefore the yield per unit area of each crop will be reduced “since all plants will be exposed to an intensified level of competition compared with the corresponding pure culture' (5). The extent to which yield of the two crops would be reduced would depend on the relative competitive ability of the coconuts and the associated crop. An interesting point to be considered is the relationship of the total yield of the association to the individual pure culture.
III. YIELD OF COCONUTS IN THE ASSOCIATION.
When the associated crop utilises the essential growth factors more than the extent to which the natural weed population did, then there would be a corresponding decline in the yield of coconuts. The intensity of competition caused by the associate would depend on its stature above and below ground and its density. Intensity of competition would decrease as both these factors decrease.
The stature of the associate above ground would indicate the extent of competition it could cause for light. Usually this would not be a serious problem as in mature stands of coconuts the crowns are held at some considerable height and nearly all crops that can be associated are far shorter in height. But with a juvenile stand, competition for light could be considerable. As far back as 1929 Clements wrote that “The plants may be so nearly the same height that the difference is only a millimetre, yet this may be decisive since one leaf overlaps the other'. Black (3) growing two varieties of Trifolium subterraneum, one with petiole length of 18 cm. (Yarloop) and another with petiole length 14 cm. (Bacchus Marsh) both alone and in mixture, showed that at 62 days, while the pure cultures yielded similar amounts the Yarloop which held its leaves well above Bacchus Marsh contributed 80% of the yield in the mixture. Similar results were obtained by Pendleton and Seif (10) where a tall variety of corn reduced the yield of a dwarf variety. In both instances the taller variety considerably
shaded the dwarf.

Page 12
Below ground level there would be competition for soil moisture and nutrients. The coconut though a tall plant is essentially shallow rooted; and most crop roots would inter mingle with coconut roots. There would always be some competition for these factors, if any are in short supply; the intensity of which will increase with the spread and depth of penetration of the roots of the associate. Little or no information is available on the extent to which competition for soil moisture would reduce the yield of the main crop, in this instance coconuts. It is however possible to visualise situations where such competition could occur. Where the roots of the two crops are stratified in depth and when available soil moisture is less than the combined demand, competition would commence; but as the upper layers dry and moisture is available at soil layers lower than the depth of root penetration of associate, then any detrimental effect of the associate on coconuts would cease. Any further effects on coconuts due to lack of soil moisture would then be the normal effects of drought. But the faster depletion of soil moisture up to the common rooting zone of the two crops would be due to the associated crop and the deleterious effect at that stage may be sufficient to cause loss of yield of coconuts.
Competition for nutrients would occur in similar manner to that of soil moisture, except that in agricultural plant communities where fertilizer application is common, a considerable proportion of the nutrients are located in the upper layers of the soil and within the root zones of nearly all crops. Competition for nutrients therefore would be of considerable importance in determining the yield of coconuts in the association. Kurtz et al (7) postulated that among the nutrients there would be competition only for mobile substance like nitrogen. Scott (18) however has shown that when alfalfa was inter planted to Sorghum, there was competition for potassium. Re-examining Salgado's (13) work on leguminous cover under coconuts Santhirasegaram (17) showed that there was competition for nitrogen and potassium and possibly for phosphorus also. Extent of competition for nutrients would also depend on the ability of the various associate crops to extract these nutrients from the soil complex in relation to the coconuts.
5

As the density of a crop decreases, the demand on the essential factors also decreases. Thus the effect of the associate on the yield of the coconuts could be reduced by decreasing the density of the associate. Where the associated crop is pasture this is difficult due to the nature of the growth habits of our pasture species. But with fodder crops such as guinea and napier grasses and such short crops such as pineapple and manihot this is a distinct possibility. With still bigger and errect growing plants such as papaw, bannana, coffee and cocoa not only the density could be reduced, their position in relation to the coconut could also be determined. Unfortunately no information is available on these even with cropping systems other than coconuts.
Be it competition for soil moisture or nutrients, the associated crop would cause considerable reduction in yield of the main crop. Pendleton et al (9) observed 15% reduction in yield of corn when interplanted to alfafla. Staniforth and Weber (19) recorded 10% reduction in yield of soyabeans due to weed infestation and Santhirasegaram (16) obtained 25 and l6% reduction in yield of wheat in 7" and 14" spacing respectively when a pasture mixture was undersown. With coconuts Salgado (12) observed 47% reduction in yield of copra due to napier grass and Santhirasegaram (17) observed 28 and 13% due to ungrazed and grazed swards of Brachiaria brizantha respectively. All these data were obtained in the absence of additional manuring or irrigation to the mixed crop. In Table l are given yield of coconuts and the trends under various pastures at two locations.
TABLE 1.
Bandiriippuwa Ratmalagara
Yield Trend Yield Trend
Weed control 352 - 5085 - B. brizantha (ungrazed) - - 3672 - 19. B. brizantha (grazed) 3737 -- T3 4,446 - 102 B. miliiformis ( , ) 3726 -- 12 - - P. maximum ( , ) 3243 -99 س - -
(Mean yield (Number of nuts/ac. /year and the trend with time relative to the control of weeds (nuts/ac./year) (17).

Page 13
When the nixed crop was given additional manure the reduction observed with coconuts by Salgado (12) was completely eliminated and in the same environment Santhirasegaram (17) observed no reduction in the yield of coconuts by B. brizantha. It therefore appears that in this environment with 85' annual rainfall, well distributed over the year any competitive effect of the associated crop was purely nutritional. This is a very encouraging prospect indeed for intercropping with coconuts. Based on this it may be concluded that in Ceylon monospecific grass swards could be cultivated with coconuts in areas with at least 85" rainfall and as well distributed as at Lunuwila provided that two crops are adequately manured.
If grasses could be grown with adequate manuring without loss of coconut yields, then it should be possible to cultivate other graminacious crops such as paddy and other cereals. The majority of the cereals would be intermediate in stature between Brachiaria brizantha and Pennisetum purpureum. There is at the moment a tremendous drive to grow paddy under coconuts and some very encouraging yields have been obtained. As long as both crops are adequately manured there is no reason why this should not be a success, and open out large areas of coconut lands for the purpose. The cultivation of paddy could be extended to areas with rainfall even less than 85' on the simple theoretical grounds that it would be harvested with the onset of the dry season, whereas pasture and fodder crops would continue to grow, unless arrested by managerial means, so long as there is some soil moisture and thus hasten the drying of the soil at least down to their root depth. In the case of a pasture however nearly all of the nutrients are returned to the soil, but in a cereal crop considerably more would be removed in the grain and straw. It would be necessary to return all the straw and compensate for the nutrient removed in the grain. Further in the case of a pasture with the incorporation of an effectively nodulating legume it may be possible to eliminate competition for nitrogen.
This augmentation of soil nitrogen by the legume opens
up an even wider prospect for intercropping with coconuts. The value of nitrogen manuring to coconuts is being realised
7

more and more. Nitrogenous fertilizers are rather expensive. If by growing a leguminous crop under coconuts some nitrogen can be added to the soil then the income to be derived would be even more. Crops such as black and green grams, ground nuts, beans and peas do not differ in stature from pasture and fodder grasses and would complete their growth with the onset of the dry periods. The evolution of a rotational system of associate cropping under coconuts where a cereal benefits from the nitrogen fixed by the previous leguminous crop is not beyond the realms of possibilities.
It is an accepted fact that in any system the efficiency decreases as the number of stages in the production line increases. In this respect production from pasture is less efficient than from other harvestable crops such as paddy and legume seeds. Donald (6) comparing pasture and crop production stated that “Broadly speaking an area which will produce 100 lb. of carbon as crop food stuffs will yield only 5 to 20 lb. of carbon in the form of meat or milk products', and goes on to say that “the energy production per acre of crops ranges from about l.5 to 10 million Kcals, per acre, whereas the corresponding figures for meat and milk are from 0.2 to 2.2 Kcals'. Similarly Allden (I) using energy as the sole criterion showed that under Adelaide conditions a wheat/pea rotation would support ten times as many people as will fat lamb production on sown pasture per unit of land. Further at present there is no efficient dairy or beef cattle in Ceylon. The Sinhala the indigenous breed of cattle found in large numbers in coconut estates could hardly be described as a dairy breed.
TABILE 2.
Product Yield Energy Protein Fat
(lb.) (Kcal. x 106) (lb.) (lb.)
Rice 1840 2.4 05 9 Soya bean 43() 2.3 500 260 Milk I5() 0.2 22 42 Meat 42 0.2 2. 40
(Comparison of production per acre from crops and pastures (6).

Page 14
Growing of pineapples under coconuts would be similar in nature to pasture. But the effect of bigger plants like papaw, bananas, coffee and cocoa are difficult to predict. It may be that their effect would be proportional to their stature particularly below ground.
IV. YIELD OF THE ASSOCIATE CROP
Little or no information is available on the effect of the main crop on the associate. Santhirasegaram (16) observed 70% reduction in the yield of pasture sown with 7 or 14 wheat compared to the pastures sown alone. Whether there is competition for soil moisture and nutrients or not, the yield of the associated crop would always be less in the association than in its pure culture, purely due to the reduced light available beneath the main crop. Black (2) reviewing the available literature on crop growth and light concluded that growth increased with increase in the available light energy. Santhirasegaram (16) obtained similar relationship for subterranean clover grown beneath wheat crops (Fig. 1). Under
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a mature stand of coconuts only about 40-60% of the solar radiation reaches ground level; and in the absence of competition for other factors the maximum growth to be expected from the associate crop would only be in that region.
A notable feature of the light microclimate beneath a mature stand of coconuts is the wide variation in intensity. With the movement of the sun, the shadows of the palms move thus exposing different parts of the ground to direct sunlight at different times of the day. The centre of the “coconut square' usually received more light than any other part. This central region, the furthest point from neighbouring palms, usually contains the least amount of coconut roots particularly due to the circular method of manuring practiced in most estates. It usually carries a more luxurient growth of weeds and pasture during the major part of the dry periods. This would result in wide variation in the yield of crops like pasture and cereals within a square, maximum growth being possible at the centre of the square and decreasing as the base of the palm is approached. If these observations are real then it should be possible to minimise competition to the advantage of both crops particularly with tree forms like, papaw, bananas, coffee and cocoa.
In the establishment of pastures beneath cereal crops advantage is made of the widening of the cereal rows and planting the pasture between the rows of the cereal. In an experiment in Adelaide Santhirasegaram (16) obtained a 100% increase in the yield of pasture when it was planted between than with the rows of wheat. Similar results have been obtained with other associations. A parallel development may be visualised when the latest methods of planting coconuts in hedges (8) and avenues (de Mel personal communication) are adopted with coconuts. These row plantings of coconuts compared to the present square method would then pose the fascinating possibilities of row orientation. In the higher latitudes rows of cereals orientated in N - S direction yielded more than E - W orientated rows; and growth of intercrop was also superior in N - S rows (16). It is difficult to predict what effect row orientation would have on the yield of coconuts in our equatorial latitudes; but if light is the limiting factor in intercropping it would appear that in E - W orientated rows
10

Page 15
of coconut, direct sun-light would reach the interspace for most part of the day and year. Where such direct sunlight would cause serious evaporation, then the photosynthetic advantage may well be offset.
V. YIELD OF THE ASSOCIATION
From the foregoing it is obvious that both the yield of coconuts and the associate crop would be less in the association compared to their yields in pure culture as long as no adjustments are made by way of manuring, irrigation, density and arrangement of the plants of the crops. When no such adjustments are made it is not yet known what the total yield of the association would be in relation to the yields of any of the crops in pure culture. The possibilities are that the total yield would be less, equal or more than the yield of coconuts cultivated alone. The total yield would not be more if in pure culture, coconuts exploit all the growth factors to the fullest extent and there is nothing wasted. This could hardly be said of coconut plantations. The luxurient growth of weeds when unchecked is alone sufficient proof. Further at least 40% of sunlight reaches ground level and soil moisture is certainly not a limiting factor during the mons oons. In an experiment in Adelaide Santhirasegaram (16) obtained a higher total yield of wheat and pasture in association than the corresponding pure cultures
(Table 3).
TABLE 3.
Pure Mixed Total of Spacing -
Wheat Pasture Wheat Pasture Mixture
7" 896 854 815 25 030 14", 630 652 7.59 185 944
Dry matter yield gm./m of wheat and pasture in pure and
mixed culture. (l6)
The annual rainfall in Adelaide is 22' and during the major part of the growing period less than 20% sunlight reached the pastures beneath the wheat. Competition for nutrients would then be the most important factor in intercropping with coconuts,

The acceptance of intercropping as an agricultural practice would depend on to what extent the total yield of the association warrants the total expenditure of cultivation. Success no doubt would depend on additional fertilizers required. In this respect a leguminous crop or a legume component in the crop would not only reduce or eliminate competition for nitrogen, but may even supply this rather expensive nutrient to the advantage of the coconut palm. As already stated reduction in the number of stages leading to the edible product of the associated crop would increase the efficiency of production and thereby increase profits.
WI. BIBLIOGRAPHY.
I. Allden, W. G., (1959) Seminar, Energy balance at the
Earth's surface. Univr. Adl.
Black, J. N., (1957) Herb. Abst. 27.
Black, J. N., ( 1960) Aust. J. Agr. Res. l.
Clements, F. E.; Weaver, J. E.; Hanson, H. (1929)
Carnegie. Inst. Wash. Publ. 398.
5. Donald, C. M., (1963 a) Advan. Agron. 15. 6. Donald, C. M., (1963 b) Aust. J. Sci. 25. 7. Kurtz, T.; Milsted, S. W.; Bray, R. H. (1952) Agron. J. 44. 8. Liyanage, D. V.; (1955) C. C. Q. V.
9. Pendleton, J. W.; Jackob, J. A.; Slife, F. W.; Bateman,
H. P.; (1957) Agron. J. 49.
T0. Pendleton, J. W.; Seif. R. D. (1962) Crop Sci. 2. ll. Pieris, W. V. D., ( 1944) Cey. Sess. Paper W. 12. Salgado, M. L. M.; ( 1944) Ann. Rep. C. R. I. 1940. 13. Salgado, M. L. M.; (1950) Ann. Rep. C. R. I. 1950. 14. Salgado, M. L. M.; (1961) Cey. Coconut Planters Rev. . 15. Salgado, M. L. M.; (1963) Cey. Coconut Planters Rev. 3. 16. Santhirasegaram, K.; (1962) Ph. D. Thesis. Univr. Adl.
17. Santhirasegaram, K.; (1964) Ann. Sess. C. A. A. S.
Sect. B. Abst. -
18. Scott, W. O. D.: ( 1960) Dis. Abs. 20. 19. Staniforth, D. W., Weber, C. R.; (1956) Agron. J. 48.
12

Page 16
ESTIMATIONS OF LOSSES AND ERODIBILITY
OF TEA SOLS
DURING THE REPLANTING PERIOD
H. N. HASSELO ANI) M., SIKURAJAPATHY
OIL losses due to erosion depend on slope length and gradient of a specific field, soil erodibility, conservation measures, cropping and management.
In tea cultivation, a vulnerable period for soil losses occurs when sloping tea land is exposed during replanting, i.e. the period between the time of uprooting the old tea until the replanted tea has covered the soil again. Generally, this covers a period of 4 years, comprised of l to 2 years after the old tea has been uprooted and during rehabilitation of the land with, for instance, Guatemala grass, and 2 to 3 years from the time the Guatemala grass has been uprooted until the replanted tea has covered the soil again.
The most critical periods during replanting occur when the soil is bare during several months after the old tea has been uprooted and removed and until the Guatemala grass has covered the soil, and from the time the Guatemala is uprooted until the replanted tea has closed in again.
The aim of this study is to estimate soil losses occurring during these critical periods in order to see
whether intensification of soil conservation measures (see
also Elias, (2)) during the replanting period would be worth considering. -
METHODS
Four plots (No. 1-4) with slopes differing in length and gradient were selected in Fields Nos. 7 and 8 of St. Coombs Estate in the beginning of 1964. Two of these plots (No. 2 & 4) were planted with tea in July 1962, that had not fully closed in. The other two plots (1 & 3)
13
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consisted of sites where the old tea and Guatemala grass respectively had just been uprooted. The tea stumps were removed but the Guatemala grass was left as a mulch on the plots.
The soil eroded from these plots was recovered from drains at the bottom of each of the four sites. In addition and as a check, three Aluminium boxes (2ft. long and lift. wide) were dug into the soil in plot 3 for recovery of soil losses. Details about these plots are given in table 1.
TABLE 1.
Erosion plots in Fields 7 and 8, St. Coombs,
Slope
ಕ್ಷೌd >:: Gradient Soil Cover
Length Widt
ft. degrees 'o
lik 7 54 29 14. 25 bare after tea
2-k 7 54. 33 13 23 Tea (l's years old)
3 8 23 6 35 70 bare after Guatemala grass ჭA**** || 8 5 4. 35 70 bare after Guaternala grass
4. 7 33 6 26 49 Tea (l' years old)
*plots l & 2 situated next to each other
istance between two contour drains *mean of three Aluminium boxes in plot No. 3
RESULTS
Soil losses in tons/acre from four erosion plots (see table I) are shown in Figure 1.
Fig. l. Soil losses (tons/acre) and rainfall (inches) on different dates (i.e. 28/4-l. 3'; 29/4-0.5"; 6/5-0.8": l3/5-1.8"; 16/6-l. 2' and 4/7-2.0") in plots 1-4 (broken line in plot 3 represents soil collected in Aluminium boxes). Note: extra losses were incurred in plots 3 and 3A owing to pre-tea planting operations (digging of plant holes etc.) during June and July.
14

Page 17
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It will be seen from Fig. l that soil losses were largest on the bare soil in plots 1 & 3 (after tea and Guatemala grass respectively), followed by plots 4 and 2, which were planted with clonal tea in July 1962 at 4' across and 12' to 2' along the contour (see plates 1, 2A & 2B).
Total soil losses on the bare soil in plot l were mainly caused by 4 high-intensity rainstorms and were estimated at 23.5 tons per acre within a period of 2% months or a loss equivalent to a layer of 0.16" of topsoil. Taking the organic matter content of the topsoil at 5% and its C/N - quotient at 10 (ll), soline 14 tons/acre of organic matter were lost, which contained about 130 lbs. N.
Total soil losses on the bare soil covered with Guatemala grass mulch in plot 3 were estimated at 14.5 tons or a layer equivalent to 0.10" of topsoil containing 0.73 tons of organic matter and 80 lbs. N. The amount of soil collected in the period 13.5 to 4.7.1964 was calculated at 10.9 tons/acre, whilst in this same period 7.8 tons/acre are estimated to have been recovered in the Aluminium boxes placed in the same plot. It would appear, therefore, that the use of drains at the bottom of a slope rather than a limited number of boxes is a more satisfactory method for estimations of soil losses.
Plots 2 and 4, planted with young clonal tea, showed reduced rates of erosion, soil losses being estimated at 3.0 and 4.9 tons/acre respectively in the period under consideration (see Figure 1).
Taking into account that the weather during the first half of 1964 was exceptional owing to the virtual absence of torrential intermonsoonal thunderstorms, and that the above data on soil losses cover a few months only, soil losses during the 4 year replanting period might be conservatively estimated as equivalent to a layer of 15 ' to l" of topsoil, or between 75 to 150 tons of topsoil per acre, containing 35 to 7's tons of organic matter with 400 to 800 lbs. of Nitrogen. These amounts are of the same order of magnitude as those reported by Holland and Joachim (9). They estimated losses on steeply sloping tea plots (gradient 30; slope length 20 feet) at 50 to 100 tons of soil containing 5 to 10 tons organic matter, 400 to 440 lbs. N
16

Page 18
300 to 500 lbs, K2 0 and 120 to 200 lbs. P2 05 per acre in six years, or the equivalent of a soil layer of l' in 7 to 20 years.
ERODIBILITY OF TEA SOILS
Losses of the order of 100 tons of soil per acre containing 5 tons of organic matter will adversely affect the productivity of the eroded land, thus further aggravating the disadvantages of existing large productivity gradients on
sloping tea fields (4).
In order to reduce these losses by the application of mechanical conservation practices, it would be necessary to segregate and evaluate the effect of soil erodibility, topography (slope length and percentage) and rainfall (amount and intensity) on soil losses.
Extensive and detailed investigations by Wischmeier et al (10, 12, 3) led to the evaluation (by means of empirical equations) of factors, which determine soil losses.
Olson and Wischmeier (10) introduced the following soil-loss
equation :
A - R K L S CP,
where A is estimated soil loss (ton/acre), R is rainfallerosion index, K is soil-erodibility factor and L. S., C and P are factors for length and percentage slope, cover and mechanical conservation practices respectively, K is defined as the average soil loss per unit of R from continuous fallow on a plot 72.6 ft long on a 9% slope.
Ignoring the factors C and P, and transposing the
terms in the erosion equation, soil erodibility can be estimated from :
K A
R IL S ”
In the absence of information on the factors R, L and S under Ceylon conditions and in order to obtain at least some measure of the relative erodibility of the soils in plots 1-4, the values of R. L. and S were estimated from empirical data obtained (13) under conditions prevailing in the U. S. A. (table 2).
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Though for reasons stated the K-values computed in table 2 should be viewed with caution, they fall in a range which would indicate a very low erodibility of the tea soils in plots 2-4. This would be in line with observations made in the field (8) viz. that the tea soils of Ceylon are very resistant to erosion. K-values of 0.02 were found by Olson and Wischmeier (10) to represent soils with a high percentage of very coarse material on the surface, while coarse-textured soils had K-values ranging from 0.08 to 0.30, and the more erodible medium to fine textured ones from 0.25 to 0.50.
TABLE 2.
Soil-erodibility (K) values in plots 1 - 4 for rainstorms of 28th April and 13th May 1964. (see also table l)
R R. Date 'E.R.E.E. S. L. K
inch.
l (bare) 28/4 l. 3 l4. 42 9.95 4 .. 6 (). 3
do 13/5 1.8 3. 10 10.0 4.6 0.06 2 (tea) 28/4 l. 3 2. () 9 95 3. 0.05
to 3/5 .. 8 (). (). 40 部。出 (). ()
3 bare) 28/.4 .. 3 3. 64 9 • 95 1 | 0 • 6ችች ; () : 03 do 3/5 .. 8 I ، 58 } } () . 4,{) : l)0( 6 م*{**** ; )( }(H
3A (bare) l3/5 l .. 8 20 (). A() 9 . L**** || )( 1 () و 4 (tea) 28/4 l. 3 . 64 9.95 8 . {****:: }{ )( 02) و to 3/5 .. 8 () . 7 (). 40 8 1 و**k || () . ()I
* Soil-loss ratio adjustment for length and degree
of slope (see 8)
* estimated by extrapolation from curves given by
Wischmeier et al. (13).
The higher K-values obtained for the first (28/4) as compared with the second (13/5) rainstorm after the dry season would suggest that the resistance to erosion is less when the soils are dry. This finding also confirms obser. vations made in the field (2).
Furthermcre, it is interesting to note that the quantitative erosion rates of slopes with low gradients (plots 1 and 2) were found to be 5 times larger for the first
3 18

Page 21
rain-storm (28/4) after the dry season than for the second one (13/5), whereas they were only twice larger on the very steeply sloping plots 3 and 4. A major difference between the soils of these two sets of plots, is that plots 1 & 2 have top-soils rich in organic matter, whereas there was little or no organic matter in the topsoil of the steeply sloping plots 3 & 4, presumably owing to continuous removal by erosion, even when the soil is covered by mature tea bushes. Further, the topsoils in plots l & 2, as distinct from plots 3 & 4, became structureless and powdery when dried out. It is along these lines that the higher erodibility of the soils in plots I & 2 might be explained.
CONCLUSIONS:
The results shown in Fig. l and table 2 indicate that:
I. soil losses on the steeply to very steeply sloping tea land of Ceylon are very large during the four year replanting period, particularly
after pronounced dry periods, and
when the soils are bare (after the uprooting of tea or Guatemala grass)
4. and their topsoils rich in organic matter:
5
the erodibility of tea soils is low, though probably much lower for the subsoils than for the organic tops oils.
SUMMARY AND PRACTICAL CONSIDERATIONS
Soil losses due to erosion were found to be very large in 4 plots laid out on sloping tea land, not withstanding the presence of contour drains at intervals of between
50' and 20.
The evidence supplied suggested that these losses were due to steepness of the slopes and high-intensity rainstorms in the intermonsoonal periods rather than to the erodibility of tea soils per se. Soil losses were particularly large on exposed tea land, as is the case during the replanting period (after the uprooting of old tea and Guatemala grass, the pre-tea planting operations and in young tea replantings) and after pruning (4). Losses were estimated at 00 tons
19
-

of soil per acre containing several tons and hundredweights of organic matter and nutrients respectively during a replanting period of 4 years on an average sloping tea field with contour drains at intervals of between 201 and 50'. It would appear, therefore, that the usefulness of contour drains is greatly reduced, if the soil collected in them is not returned to where it came from.
The results also showed that erosion rates were doubled after prolonged dry spells and even more so on soils with topsoils rich in organic matter. It might be inferred from the latter, that the benefits of careful soil-management in the past may be quickly lost during replanting.
There is insufficient quantitative evidence to suggest an optimal drainage system on fields with different soils and gradients and in varying climatical conditions. However, it would be good conservational practice to avoid, as much as possible, exposing tea soils during prolonged spells of drought and to intensify anti-erosion practices during the critical replanting operations. In this respect, it might be well to remember the following: to keep the soil surface rough rather than smooth, and to maintain the old drainage system after uprooting the old tea, to plant Guatemala grass very close in the rows, to give weeds a chance to grow some time before the tea is uprooted, to lay out a new drainage system only when the soil is covered, to reduce as much as possible the time interval between the uprooting of old tea or Guatemala grass and the planting of Guatemala grass or young tea respectively, and to thatch young tea clearings, especially during prolonged dry spells.
Soil losses, resulting in denudation of the upper parts of slopes and colluviation at the lower end, will affect the productivity of the land (4). The occurrence of large productivity gradients may interefere with the eficient use
and management of sloping tea land. Examples are published
elsewhere and deal with the topographical sequence of soils on sloping land in relation to fertiliser practices, the lay-out of fields on a tea estate, the design of experiments, the choice of land and clones for replanting (3, 4) the interplanting of shade trees (5), the efficiency of chemical weed control by means of herbicides (7) and the mineral composition, particularly of manganese, of tea leaves and
20

Page 22
crop (6). It is obvious that the many different aspects of such a soil pattern or toposecuence (l) are very important from the fertility and management point of view and, therefore, should be recognised in soil mapping
REFERENCES
I. Coulter, J. K. (1964). Soil surveys and their application in tropical agriculture. Trop. Agrie. (Trinidad), 4; 185-196.
2. Elias, A. L. (1961). Planning New Clearings: Recent experience at St. Coombs. Tea Quart. 33, 4: 202-212. 3. Hasselo, H. N. (1962). Tea roots show effective depth
of soil. Tea Quart. 33: 45. 4. Hasselo, H. N. (1964). Productivity gradients on sloping tea land in Ceylon. Tea Quart. 35 (in press). Hasselo, H. N. (1964a). Some observations on the growth rate of shaded and unshaded tea on sloping land. Tea Quart. 35 (in press). 6. Hasselo, H. N. (1965). Leaf nutrient contents of tea
(in preparation). 7. Hasselo, H. N. and Sanda namn, S. (1965). Chemical
weed control in tea. (in preparation). 8. Haworth, F. (1952.) Report of the Chemical Division for 1951. Rep. Tea Res. Inst. Ceylon: 26-27. 9. Holland, T. H. and Joachim, A. JAV. R. (1933.) A soil erosion experiment. Trop. Agricst, (Ceylon), 80:
99-207. 10. Olson, T. C. and Wischmeier, W. H. (1963.) Soil-erodi. bility evaluations for soils on the runoff and erosion stations. Soil Sci. Soc. Anaer. Proc. 27: 590–592.
II. Tolhurst, J. A. H. (1956). Report of the Agricultural Chemist for 1955. Rep. Tea Res. Anst. Ceylon: 26-32.
12. Wischmeier, W. H. (1959.) A rainfall erosion index for a universal soil-loss equation. Soil Sci. Soc. Amer. Proc. 23; 246-249.
13. Wischmeier, W. H. Smith, D. D. and Uhland, R. E. (1958.) Evaluation of factors in the soil-loss equation. Agr. Eng. 39; 458 — 462.
5
2.

THE SMALL TRACTOR It's uses and limitations in the mechanisation of Ceylon's Agriculture.
W. E. A. WIKRAMANA YAKE
HE mechanisation of Agriculture is one of the corner stones of National development, and the use of small power units is the only way by which mechanisation can be realised without seriously changing the existing sizes and patterns of land holdings. The small tractor (two-wheel, walkie', Power titler etc.) which originally served the small market garden in the West, has rapidly found popularity in S. E. Asian countries faced with problems similar to those of Ceylon. In the early days of their introduction it had often been said (with some justification) that a farmer must needs own three machines-one at work in the field, one in the repair shop, and one on the way from the repair shop to the field. In the last few years, however, the development of this form of tractor has been phenomenal (particularly in Japan.) and the small tractor of today is just as hardy and reliable as it's four-wheel counterpart. The idea of the small tractor is very attractive, and farmers and others can easily be led to imagine that the small tractor can be the answer to the farmer's prayer. It is proposed to outline, in this paper, some of the features of this type of machine in order to place it in the correct perspective, and to understand both it's possibilities and it's limitations.
When the idea of using two-wheel tractors in S. E. Asia was first put into practice, the primary aim of the designer seems to have been to simplify the machine in order to permit its continued use and maintainence by unskilled and technically uneducated farmers. Many machines are still marketed in this simple form - i.e. having simple engines of low horsepower, single speed transmission and no steering clutches or other devices to facilitate operation,
22

Page 23
This oversimplification has been disadvantageous in two ways. First, the strain of operation, particularly the difficulty of manhandling the machine at corners, has discouraged farmers; and second, the simplification of design has seriously limited the size of power unit that can be used, and very often such machines are short of power for the job in hand. The mistake was realised very early in Japan and corrected. The modern two-wheel tractor is of sophisticated design, and combines power with easy operation. Power tillers of 10 h.p. are being manufactured and sold and are as easy to operate as the 4 h. p. models and easier to operate than the older type of simple design. Sound extension programmes have resulted in farmers being able to maintain their machines satisfactorily, and do most of their own running repairs. In some countries (e.g. Taiwan and Japan) the compulsory testing, and conformity to predetermined standards, has protected the farmer from being foisted with inferior machines as a result of high pressure advertising.
Small tractors are of two types; the traction type which provides drawbar pull for conventional implements, and the power-tiller type (generally of larger horse power) which has a rotary tiller built into the machine. Both types are capable of being used to drive stationary machines such as pumps and threshers, and both types can be used for transport by attaching a trailer. The traction type is more versatile, but the power tiller has its uses where deep tillage is practiced. Many machines of the 5 to 7 h. p. range can by used both as traction types or as power tillers. Fig. I shows the two types and Fig. 2 a typical layout of operational controls of the modern small tractor. By far the most attractive features of small tractors are the possibility of rapid interchanging of groupid drive components, (from pneumatic tyres to steel wheels of one form or another, or tracks), low initial cost, and suitability for use on small holdings.
In assessing the suitability of the small tractor on agricultural lands, the main factors to be considered are Trafficability and Cost. Small tractors are admirably suited for rotary tillage, and some information on this type of cultivation should not be out of place in this paper.
23

FIG. (A) TRACT ON TYPE MACHINE
FC () POWER TILLER
24

Page 24
One of the most important characteristics of an agricultural tractor is the ability to move and pull loads On terrain of various types. This factor is most important particularly in Rice cultivation under wet conditions. Much work has still to be done on determining soil strength characteristics and relating them to tractor and implement
design. A method used in the assessment of military vehicles can be used within limits in the case of agricultural
t ፫á Ꮳt OS
The most important soil characteristic affecting traction is soil strength, which can be expressed as the “cone index” i.e. the force per unit area necessary to push a 30 degree cone into the soil. The “vehicle cone index" (4) is the minimum soil strength that will permit the vehicle to complete 50 passes with a maximum travel reduction of 30%. It is based on the “mobility index" - a dimentionless number obtained by applying certain vehicle characteristics to one of several formulae (depending on the type of vehicle) which take into consideration engine, transmission, ground drive, weight, ground clearance etc. The lower the vehicle cone index, the softer the conditions under which the tractor can work without undue sinkage or bogging down. Experiments under controlled conditions in soil bins have shown that this technique gives fairly consistent results with agricultural tractors In table l are given the vehicle cone indices of some 4 - wheel conventional tractors and small (2-wheel) tractors that are sold in Ceylon.
... '
It will be seen from table 1. that there is little difference in trafficability between the two types (if at all the 4-wheel tractor will have a slight edge over the small tractor). This would mean that the small tractor is as liable to be bogged down as the large tractor under Paddy conditions. Under upland conditions the hardness of the soil will have a limiting effect on the small tractor, particularly in operations such as ploughing, due to insuffi. ciency of power. This drawback is to some extent offset by the ease with which the small tractor can be adapted for rotary tillage. Means by which floatation is increased under Paddy conditions are still to be devised, and much
25
 
 

of the research in machinery in S. E. Asia consists of studies towards this end.
TABLE 1.
Tractor Mobility index Vehicle cone index
4-Wheel tractors
A. 45.2 46
B 47.8 48
C - 50. 5.
D 47.8 48
Small tractors
M 49.7 49
N 45. () 46
P 57.8 60 Q 64. () 55
ECONOMICS OF OPERATION
The most important aspect of the economics of small tractor operation is in the saving of time. This would not only increase the output per man-hour, but also confers other advantages such as achieving timeliness of operations and providing the farmer with leizure to devote to other profitable enterprises. The advantages of time saving cannot be easily assessed in terms of rupees and cents. Table 2 shows the extent to which time can be saved on some selected operations.
StART M we
って
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GEAR stLectros LEVER
RAN CLUTCH LEVER
THROT TE
Р Ү О LE VEG – STEER ING CU U TCM
F | G 2 CONT ROL S OF MODERN S MAI RACTOR
26

Page 25
TABLE 2.
HOURS PER ACRE
Operation Man with Man with Pair of Small Mammoty El Bullocks tractOr
Ploughing 64 64. 16 4 to 6 Harrowing 64. 64 4. 2 to 3 Ridging 32 24 4. 2 to 3 Seeding 16 4. 3 2 to 2% Intercultivation 48 16 4. 4.
Small tractors can also perform many operations cheaper than bullock power or manual labour. Table 3 shows comparative costs for some operations.
TABLE 3.
COST PER ACRE IN RUPEES Operation Man with Man with Pair of Small mammoty correct tool bullocks tractor
Ploughing 24.00 24.00 9. ()0 7.00 Harrowing 24.00 24. O() 5.00 3.00 Ridging 12.00 l3.00 5.00 3.00 Seeding 6.00 2.00 4.25 3.00 Intercultivation 18.00 6.50 5.00 4.00
The cost per hour of operation is made up of Fixed costs and Running costs. The fixed costs include depreciation, interest, maintainence and spare parts etc. Running costs include labour, fuel and lubricants. Fixed costs depend to a large extent on the period of annual use, and the fact that improved models tend to make a machine obsolete in a few years. Fixed costs are lowest when maximum use is made of the machine. Studies on small tractors of various types and their ancillary equipment have made possible the design of a nomogram to facilitate the estimation of the fixed costs per hour of operation. The nomogram shown in figure 3 is provisional and may need modification as more data becomes available on recent models. Three categories of small tractor are provided for viz. Category B of 5 to 7 h.p. with either wheel or track for ground
27

drive, corresponds to the pOWel' tiller. Category C is the commonly used traction type small tractor, and category D the midget power tillers of 1.5 to 2.5 h.p. Data on category C were taken from studies of small tractors of simplified design, and therefore the modern type of small tractor is
best classified in category B.
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FIGURE 3.
28

Page 26
The nomogram has four scales and a pivot line. The cost of the machine on scale A is lined up with the estimated annual use on scale B. The point at which this line cuts the pivot line, when joined to the relevant index number on scale C. and produced, cuts the scale D at the hourly fixed cost. This will include depreciation, maintainence, repairs. and interest, and allows for the obsolescence factor. It does not include wages, fuel or lubricant costs. It is regretted that it has not been possible to provide figures of the cost of operating conventional 4-wheel tractors in Ceylon for purposes of comparison, It is hoped that the Government Department of Agriculture, which has been operating such tractors in large numbers since 1948 will provide some data on costs in the near future.
ROTARY TLLAGE
Rotary tillage has long been practiced in the West to a limited extent, and is now becoming extremely popular in the Far East, particularly on account of the ease with which this system of cultivation can be adapted to the small tractor. Moreover, in recent years, much work has heen done on rotary tillage, and many of the hitherto existing undesirable effects, such as excessive pulverisation of the soil, have been eliminated. One of the limiting factors in increasing the power of a small tractor is the torque reaction of the driving wheels, which makes operation tiresome and the machine unwieldy. At low power, this torque reaction is beneficial in that it tends to keep the implement in the soil. When a rotary tiller is used, the wheels serve only for propulsion, and the bulk of the torque of the engine is provided to the rotary tiller shaft. The rotary tiller also tends to propel the machine forward. Kaburaki (l) has shown that the torque on the wheel shaft decreases with and increases in depth of tillage and can even become negative. It is a commonly observed phenomenon during tests, when travel reduction sometimes works out to a minus quantity.
On the traction type of machine, a form of rotary tillage can be performed, by replacing the wheels on the main shaft by rotary tyines. Forward motion will then depend on the thrust of the rotary tiller, and forward speed can be controlled by lifting or lowering the rotor,
29
,

using the handles as a lever working about a skid or gauge wheel acting as the fulchrum. (Fig. 4). Depth of tillage will be inversely proportional to forward speed. This type of rotary tillage is suitable for intercultivating narrow spaced crops, which must needs be slow to avoid damage to the plants, but is too slow a method of tillage for land preparation.
KWA NO LE
S K D ലഗ (Fu - с на U м)
ko TQ R yr Ali , C^ Le « N , , O
i F G 4 coMBI NED TIL LA G E 8 PROPUL SCN
Two major developments of the small power tiller are the combined fertilizer-tiller-seeder, and the technique of preparing wet paddy fields. In the former case, a fertilizer-seeder is attached to the machine so that fertilizer is metered out to the front of the rotary tiller, and the seeds sown in furrows behind it. Thus the fertilizer is spread and mixed during the tillage operation and seeds are drilled in rows--all in one pass. This system is ideally suited to conditions where paddy can be sown dry and the fields impounded with water after the plants have grown. In the latter system (Unaikaki method of Japan) (2) the ploughing and puddling of wet paddy fields is performed in one operation by the rotary tiller. Two such tillings are necessary, and the horse power hours per acre for this technique are about half that required when the land is ploughed dry aud puddled in a second operation. (l) There is also a time saving of two-thirds (2).
Japanese research on rotary tillage has been very comprehensive in recent times; notably the work of Kaburaki,
30

Page 27
Kisu and others at the Institute of Agricultural Machinery,
Konosu, and also of Sakai and Kodha, both formerly of the Kyushu University. Some of their findings relevant to this paper, are given below.
(a) The Japanese type of curved tyne needs 1/3 less power than the Western type sharply bent tyne.
(b) Maximum efficiency is obtained when the tynes on the rotor are rationally distributed, i.e. where each tyne follows a path independant of any other tyne.
(c) Knife tynes need l. l to 1.6 times more power than pointed tynes except where much grass and trash has to be buried.
(d) Tyne strength is better improved by increasing the width of the tyne rather than the thickness.
(e) Torque and power per unit area of furrow slice section is minimum at depths of 12 to 14 cms.
Rotary tillage on the power tiller principle seems to promise the solutions to Ceylon's mechanisation problems both for highland and wet cultivation conditions.
The small tractor has come a long way in the past few years. The models of a few years ago can now be considered as experimental prototypes, and have not justified in full the hopes that were placed in them. Improvements have been made to such an extent that it will be most profitable to review the small tractor and it's role in Ceylon's Agriculture, with reference to the new developments in this field, particularly rotary tillage.
BIBLIOGRAPHY
1. Kaburaki Hideo-Studies on tractor. A performance and power requirement of tractor-Jnl. Central Experiment Station, Japan, Sept. 1963.
2. Kisu Masayuki-Mechanical equipment for underwater cultivation Report of the 3rd. meeting of the Working Party on Rice Mechanisation FAO 1964.
3. Kisu. Masayuki-Results of field tests of 36 small tractors
Private communication, 1964. -
3.

Knight S. J. and Freitag D. R.–Measuring soil trafficability conditions A.S.A.E. paper No. 61-609 196l.
Kodha Yoshihiro — Studies on rotary tillage — Un published
doctoral thesis of Kyushu University 1964.
Levens /4. S. — Nomography 2nd edition.
Yamanaka Isamu — Agricultural Machinery and Imple
ments-International Trade Service Bureau 1961.
Yamanaka Isamu-Rotary tillage vs. Mould board ploughing Annual report-National Tillage Laboratory Auburn, Alabama 1961-62.
32

Page 28
TOLERANCE TO BACTERIAI, WILT (PSEU DOMONAS SOLANACEARUM E. F. S.) AND YIELD OF POTATO VARIETIES IN THE UP-COUNTRY OF CEY LON.
T. VISSER and K, CAESAR
... INTRODUCTION
BACTERIAL wilt has been recognised as one of the most severe diseases of the potato in the subtropical and tropical regions of the world (6) because it cannot be efficiently controlled as yet, while being able to destroy the crop completely. Nielsen and Haynes (15) have attempted to breed resistant varieties for many years, but as this bacterium has a wide range of host plants (li) it seems to be difficult to find hereditary resistance.
In Ceylon potato cultivation dates back from the 19th century but was probably not seriously handicapped by this disease at that time. It was reported by Petch in 1909 (17) in connection with the incidence of wilt of tobacco as related to climatic conditions and referred to by Park (16) as an important pathological problem and by Davidson (5) with regard to the relative resistance of potato varieties. The first research on potatoes in Ceylon was undertaken by Abeygunawardena and Wijesooriya (2). Results of their trials show that the incidence of bacterial wilt decreases with the rise in elevation. It was also found that the bacterium is practically absent in paddy" fields.
Kelman (ll) reports the findings of several workers on the question of the dependance upon temperature of the bacterium. Below a certain temperature, approximately 10° C., the organism will become inactive, although it is still viable when brought under more suitable conditions. Abeygunawardena's and Wijesooriya's (2) observations and those made by Abeygunawardena and Siriwardena (3), on
33

the disease incidence at different elevations can be explained by the decrease in temperature at higher elevations.
Since there is no known control for bacterial wilt, it
is important to know whether there are areas free of this disease in Ceylon for the production of potatoes. Pushkarnath (18) making use of Abeygunawardena's findings, worked out a system for the production of seed potatoes at the highest elevations from where the seed could be issued to the cultivator (at lower elevations) who has to produce consump. tion potatoes. Here a certain percentage of infected plants can be tolerated as long as the yield is not seriously affected.
With the foregoing in mind the present studies were undertaken on the one hand to find out whether there are differences in the tolerance or susceptibility of varieties and on the other hand to see whether certain kinds of land might offer opportunities for growing potatoes. Especially it was the purpose to investigate whether tea land would be sufficiently free of bacterial wilt to allow the growing of potatoes. A short term crop as potato could be used in the otherwise unproductive period of 1–2 years, elapsing between the unrooting of tea and replanting, which period is compulsory for soil-reconditioning with grass. This would also help to satisfy the demand for consumption potatoes produced in Ceylon.
In this paper the authors have preferred to use the term “tolerance” instead of “resistance' in connection with bacterial wilt, although generally the word “resistance” is used in the literature. We believe that there is no resis. tance found in potatoes yet, whatever differences between varieties exist, can be described as relative degrees of tolerance or susceptibility.
2. WLT TOLERANCE OF POTATO VARIETIES
2. l. Experiments in naturally infected land
Altogether 10 tests were carried out to investigate the tolerance of commercial potato varieties and a number of new Dutch selections to wilt at different locations. These locations will be referred to as St. Coombs, Passara and Hantane; they are at approximate altitudes of 1400
34

Page 29
(4500 ft), l050 (3500 ft) and 750 (2500 ft) meters respectively. The areas used for the experiments at these locations were vegetable gardens known to be wilt infected. The data concerned are given in Table 1.
TABLE I
DATA RELEVANT TO THE WILT TRIALS CARRIED OUT AT THREE LOCATIONS
'ನ್ತಿ! Location No. of N. Period of trial Sပုဝှိုဂf
St. Coombs 39 x 2 Febr. - May ’60 Netherlands 2 42 وو l x 3-7 Oct. '60. Jan. '6l Trial (1) 3 3 26 وو x 3 Mar. - May 6l. Netherlands 4 Passara 26 3 x 3 Aprl. - July 6l. Trial (2) 5 Hantane 13 2 x 5 Oct. - Dec. 6l. Trial (3) 6 St. Coombs 16 2 x5 Oct. 61 - Jan. '62 Trial (3) 7 99 18 2 x 5 Mar. - May/Jan. 62 All varieties
9 Passara l9 2 x 5 - do - | 2) from O Hantaine 2 2 x 5 Mar. - June 62 local sources
N. B.-Trials l. 2, 3, 6 and 8 were carried out in the same garden,
trials 7 in an adjacent garden at St. Coombs.
*) Tedria and Gineke as standard varieties.
The experiments were carried out in two periods viz. from March to May/June and from October to December/January. These two periods vary considerably in weather pattern. The weather of the March to May/June period is in the beginning influenced by the outgoing North East monsoon, towards the end the plants come under the influence of the South West monsoon; this period will be referred to as the “NE/SW season'.
The October to December/January period is during October often still under the influence of the outgoing S. W. monsoon, for the remainder predominantly influenced by the N. E. -monsoon; this period will be referred to as the “SW/NE season”. St. Coombs and Hantane in spite of their different elevations have fairly similar weather
35

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Page 30
conditions during the year, although the climate is hotter at the latter than at the former location. At both locations the SW/NE season is initially rainier, particularly during the afternoons, and cooler during the daytime than later on towards January when the weather becomes drier with temperatures which are somewhat higher during the day and lower during the night. The weather at these locations during the NE/SW season is in the beginning during February and March rather hot and dry, then becomes more humid (showers) with still relatively high temperatures and towards the end in May becomes very wet and cooler when the S. W. monsoon sets in. Passara is located in a different climatic region where the weather pattern is rather the opposite from that of the two other locations during the same period. The rainfall becomes very high from October onwards, it abates towards January, night and day temperatures are relatively low during this period. They rise in March, when the weather becomes drier and sunnier (though April brings usually much rain), June and July are the driest months (see Table 2).
The tubers in all the experiments referred to below and in other paragraphs were planted at 60 cm. (2 ft) between rows and at 30 cm. (I ft) in the rows. The areas were manured beforehand with a NPK Mg - fertilizer mixture and sprayed with Endrin against cutworm and army worms. The plants were sprayed against Phytophthora infestans with colloidal copper in the earlier trials, in the later ones with a zinc carbamate preparation; the frequency of spraying depended on weather conditions.
The 10 trials except for the first two, were replicated in situ and for about two dozen varieties also at different locations.
The potato plants were checked visually (occasionally microscopically) for wilt symptoms once or twice weekly after their ermergence. These symptoms proved to be easily recognizable on the whole.
The freshweight yields of the surviving plants were assessed at harvest time. and calculated on the number of tubers initially planted.
37
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Page 31
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Page 32
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2. l. l. Variety trials
The potatoes screened in the first trial consisted of () selection numbers mostly obtained from the late Dr. Toxopeus of the Institute for Plant Breeding at Wageningen, the Netherlands, and 21 commercial potato varieties (including some progenitors) of different origins: each variety or
nun her was represented by two tubers.
About equal numbers of varieties (162 and 157 respectively) were planted in each of two adjacent plots in the same garden at St. Coombs of which the one plot had been under vegetables (also potatoes in 1959) and one year Fallow and the other under grass for several years prior to the experiment (the latter area was sprinkled with soil from
the former plot to increase the level of infection).
As an index of tolerance to wilt served the time, that lapsed between the date of planting and the date that plants wilted or the time between planting and harvesting, for those varieties (only 7% of the total) which showed no wilt symptons at all in this test. The potatoes were then grouped according to their index in successive categories, but separately for the two plots as the potatoes in the former vegetable area became quicker infected than in the former grass area. The distribution (in categories) of the varieties and selections is shown in Fig. 1.
Both graphs in Fig. I show a skewed distribution indicating the tendency that wilt-susceptibility rather than wilt-tolerance is the rule; the plants of more than 70% of the potatoes in both groups showed wilt symptoms before maturing. Only a minority wilted at a late stage or not at all and produced a fair amount of healthy tubers.
It is also evident from Fig. I that the vegetable area was much more heavily wilt-infected than the grass area which also appeared from the mean wilting times which were 17 and 63 days respectively. As a result of this difference in infection only 10 of the 40 varieties and selections considered worthy of retesting came from the vegetable area. Although the number of tubers, per variety
was very small, namely two tubers, the high number of varieties involved allows the assumption that perennial grasses will be able to reduce the incidence of bacterial wilt.
38

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FIGURE 1.
sol GRASS ARE A
玄
2.
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so VEGE TABLE AREA
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DAYS AFT ER PLANTI NG
The distribution of potato varieties according to their relative tolerance to wilt as measured by the number of days elapsing between planting and the time that both plants (per variety) showed wilt infection (or reached maturity without wilting) in a former vegetable plot (162 var.) and grass plot (157 var.) respectively.
From the 40 varieties selected for retesting, 25 were tested in the second trial at St. Coombs, the remaining lis varieties together with 9 others (not tested in the first trial, but freshly imported) were retested in later experiments, all carried out in moderately to heavily infected plots. There is a possibility that tubers harvested from visually healthy plants were already infected before harvesting, but it can be expected that these tubers will rot in the stores during the period of dormancy and will be discarded long
139
 

before planting is due. Therefore it is justified to test the tubers harvested in Ceylon together with freshly imported tubers. (see par 2. L. 3.)
The performance of these 49 varieties was expressed by the average score for wilt-tolerance and yield respectively determined for each trial separately and is given in Table 3.
The yield score in Table 3 gives only relative information. In the first instance the number of tubers tested was rather small for a yield trial, secondly the number of tests had varied from variety to variety due to the fact that varieties were discontinued in testing if they failed in the previous test and lastly the yield of a particular variety does not depend on the wilt-tolerance only but also on its adaptability to environmental conditions, e.g. the day length and temperature in the tropics. Nevertheless it will be seen in Table 3 that the most tolerant varieties also show the best yield score.
As judged by their average score, the majority of the 49 varieties must be classed as having poor to moderate tolerance, a number of varieties such as e.g. Eigenheimer, Green Mountain and Kathadin yielded in some trials reasonably well, though most plants showed signs of wilting at harvest. Gelderse Rode and Zeeburger showed considerable tolerance initially, but performed only moderately in the last series of tests so that their average score indicates only a somewhat better than moderate tolerance- The 4 varieties which showed consistently the highest tolerance to wilt (while producing a good yield, see Fig. 3) in the various tests at 3 locations and thus obtained the highest scores were Ambassadeur, Hilla, I. V. P. 654 and Noordeling.
A number of varieties were tested in all 3 locations in 1961 and 1962. For the purpose of illustration, the average wilt performance determined in these trials of seven varieties is shown in Fig. 2.
The trends shown by these varieties are more or less in accordance with the scores given in Table 3: Tedria appears to be very susceptible followed by Eigenheimer, the other varieties appear more tolerant. While Eigenheimer and Tedria show similar results in both years the other
40

Page 34
PERCENTAGE PLANTS WITED
FIGURE 2. |- : 10-os-|-©| V «No /& &QL|-
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●...·_ mcoő- - ( )o.·* 220おQ●●8€.26| 4o)60 )80
DAYS AFTER PLANTING
The performance of potato varieties tested in1961 (black lines and dots) and in 1962 (brokenlines andscircles)T
+ -=*
at 3 locations as measured by the average percentage of plants wilted in relation to time after płanting. : ( )本
 
 
 
 

four varieties show a faster and higher rate of wilt in 1962 than in 1961. The reason for this behaviour is not quite clear, possibly it is a kind of a physiological degeneration due to the growing and storing under warmer conditions.
It can be further noted from Fig. 2 that the susce
ptible varieties become infected earlier and at a faster rate than the tolerant varieties.
FIGURE 3.
15o
200
150
OOL
5○|-
O - --- = "می . س L
O 2O 40 6 O . 8 O OO
PERCENTAGE PLANTS WILT ED AT HAR VE S T U
Loss of crop in relation to the percentage of plants wilted at harvest
(averages of two series of tests): circles indicate the position of 8 varieties common to both series.
A -- Ambassadeur GI — (Gineke T Tedria E – Eigenheimer H — Hilla
Z - Zeelburger G = Gelderse Rode I — . T. V. EP. 654,
The extent to which the tolerance of a variety as expressed by its wilt percentage (percentage plants wilted at harvest), is also a measure for its yield can be seen from Fig. 3. This Figure presents the yield (of healthy tubers only) as a function of the Wilt percentages recorded in the two series of tests carried out in 1961 and 1962
(see Table l) on 20 varieties in all. These tests comprised
42

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108 individual observations on wilt infection (each observa. tion on 10 tubers) which were arranged in 10 successive wilt-percentage classes (0, 1-10, 11-20, ........ ...91-100% wilt). The Figure also includes the records on the 8 varieties common to all tests in order to show their relation to the average regression. It can be seen that the yield is inversely proportional to the percentage of plants wilted at harvest. It also appears that Ambassadeur, T. V. P. 654, Hilla and Gelderse Rode were the best performers in these tests : Zeeburger and Eigenheimer take up an intermediate position: Gineke and Tedria, are at the bottom indicating that their cultivation in infected soil would lead to complete failure.
2. II. 2. influence of tuber conditiona
Since it is a common practice in many of the potato growing countries to cut tubers in half in order to obtain a higher number of plants from a smaller seed stock it was a matter of interest to know" whether this facilitates subsequent infection in the soil.
For this purpose an experiment was carried out with Eigenheimer, I. V. P. 654 and Tedria comprising 3 treatments:
(a) tubers whole - (b) tuber halves, air dried for 4 days before planting
(c) tuber halves, cut at planting.
The trial was replicated 3 times with 6 tubers per variety per treatment per replicate (in total 54 tubers per treatment) and carried out at St. Coombs in a moderately infected area during April/June 1962.
It was found that cutting the tubers into halves had no effect on early rotting in the soil as áll tubers, whether whole or halved, produced plants; it had neither a signifi. cant influence on the wilt percentage of the plants at harvest time, which amounted to 24, 20 and 19% for treatments a, b and c respectively. Cutting the tubers into halves significantly reduced the yield, as the tubers halves produced on an average 30% less crop than the whole tubers: drying of the halves before planting had no effect on either yield or wilt infection.

2. i. 3. Influence of tuber source
As indicated by Table I, some trials were carried out with seed potatoes obtained directly from the Nether. lands and thus could be assumed to be wilt-free, other trials were done with seed tubers which originated from St. Coombs and could be assumed to be contaminated by wilt. This was very evident from the losses which were sustained in several cases during storage notwithstanding the careful selection of visually healthy tubers for storage, which seemed also related to the susceptibility of the variety in the field. For example, often more than half of the tubers of Tedria were lost in the first month of storage, whereas e. g. tubers of II. V. P. 654 or Ambassadeur rarely rotted during storage.
As to the effect of tuber source on the performance in the field an impression can be obtained from the comparison of trial No. 1 which was planted with 2 tubers per variety with trial No. 2 which was planted with 3-7 tubers per variety, carried out in 1960 at St. Coombs. For the same purpose trial No. 3 planted with 3 x 3 tubers can be compared with trial No. 6 planted with 2 x 5 tubers carried out in 196l likewise at St. Coombs (see Table J). The first trial of each set of tests was carried out with freshly imported tubers, for the second trial tubers from the first trial which appeared visually healthy were used. The 4 trials had () varieties in common, viz, 3 tolerant
varieties — I. V. P. 654, Noordeling and Zeeburger — and 7 susceptible varieties - Bevelander, Eigenheimer, Fransen,
Gineke, Merkur, Valenciana and Voran. The results of the two pairs of trials averaged for the resistant and suscepti. ble varieties separately are given in Table 4.
AB .
The effect of tuber source (Netherlands, un contaminated: St Coombs contaminated) on the average yield performance of tolerant and susceptible varieties grown in two successive seasons during 1960 and 1961 (Yield in grams per tuber planted)
Average 1960 . tubers from 1961 - tubers from Average Diff.
for Nether. St. Coombs Netherl. St. Coombs
Mar.-May Oct.-Dec. Mar.-May Oct.-Dec. 1960 1961.
3 tol. var. 263 359 226 245 Bll 235 27%
7 Sus. Var. 280 256 46 37 268 142 479

Page 36
it will be seen from Table 4 that the seed tubers propagated in infected soil did not yield any less subsequently than tubers from the Netherlands under the same conditions of soil infection. By comparing these figures it has to be borne in mind that the October - December season is more favourable for potato growing than the March - Ivay season. It is of interest to note that only the 3 tolerant varieties are able to make use of the better weather conditions resulting in higher yields. Noteworthy is further the differ. ence in yield between the years 1960 and 1961. It was already mentioned that planting was done on the same place. The yield, however, is mainly influenced by weather conditions but in this particular case the incidence of wilted plants was higher than in the previous year, especially among the susceptible varieties. This leads to the assumption that planting without proper rotation increases the level of infection of the soil, which affects the susceptible varieties more than the tolerant ones.
This aspect was further investigated in an experiment at St. Coombs in 1962 (April - June) in which use was made of uncontaminated tubers of Ambassadeur, Eigenheimer, Tedria, Il. V. P. 654 and Gelderse Rode. The uncontaminated tubers of the first 3 varieties originated from a field trial in tea land (40 years tea previously) at St. Coombs, tubers of the latter two varieties came directly from the Netherlands. The contaminated tubers originated from a second generation propagation in infected soil at St. Coombs. The two treatments were 4 times replicated for each variety with 4 tubers per plot (64 tubers per treatment); the experiment was carried out in moderately infected soil.
Fig. 4, which presents the curves for wilt infection of the plants with time (both linear on log scale), shows that the wilt percentage of the plants grown from contaminated tubers increases more with time than that of plants grown from non-infested tubers, the difference is, however, not significant. The yields did not differ significantly either and averaged 102 and 103 grs per planted tuber respectively.
Accordingly, the propagation of seed tubers in infected soil did not appear to have a significant influence on the
subsequent performance of the plants in the field. This somewhat unexpected result is attributable to the careful
45

1- HGURE 4.
4o
30 -
2.
O
مير
كامير
صميمܐ
ހ.
GRسمصر
ம O 3O 40 50 6 O DAYS AFTER pull ANT INC ( LOC, SCALE)
Ο
The performance of contaminated (broken line) and uncontaminated (black line) tubers as measured by the average percentage of plants wilted in relafion to time after planting.
selection of visually healthy tubers for planting. It also substantiates the likelihood that tubers which are infected, but do not show it at the beginning of their storage, are automatically eliminated from planting as they will rot subsequently under the relatively warm storing conditions which favour the development of the bacterium. Another question is whether these storing conditions, considered as less favourable in the potato growing areas in the temperate zone, will have an unfavourable effect with respect to vigour or degeneration and may result in lower yields after several times of multiplication.
2. II. 4. Environmental influences
A certain annount of environmental influence on the performance of the potatoes can be derived from several replicated tests which had the same 6 varieties in common (Ambassadeur, Eigenheimer, Gelderse Rode, Hilla, I. V. P. 654, Zeeburger) and were carried out in different seasons, years and locations. These tests are (see also Table l):
46

Page 37
NE/SW Monsoon season SW/NE MO soon season
trial (3) : St. Coombs 1961 trial (6) : St. Coombs 1961. , (7) : St. Coombs 1962 ..., (5) :: Hantaine } 96. ..., (10) : Hantaine 962
The average percentage plants which wilted in the period between planting and harvesting is shown in Fig. 5.
lt can be seen from Fig. 5 that the wilt curves for the SW/NE season of 1961 (black lines) are similar for the two locations. Wilt infection during the NE/SW season (broken lines) at St. Coombs was in 1962 the same as in 1961, but notably more severe-Wilting started 15 days earlier than during the SW/NE season. At Hantane, the difference between the two seasons is even more marked; during the NE/SW season the infection at this location, the climate of which is hotter was also much higher than at St. Coombs.
In accordance with the observed trends on Wilt infection the average yield for the 6 varieties at St. Coombs was for the NE/SW season 32% lower than for the SW/NE season (312 versus 214 gm) and 79% lower at Hantane (163 versus 34 gun). No doubt the difference in favour of the SW/NE season at St. Coombs and Hantane is due to the somewhat lower temperature and a more favourable distribution of rain than that prevailing in the other
8 £aᏚ Ꭴ !Ꮢ .
2. 2. Experiments in artificially infected and
The testing of potato varieties started by Abeygunawardene and Siriwardena (2) in 1958 was intensified by the second author of this paper in 1962. All varieties to be planted in the governmental farms were tested first in the artificially infested soil at the up-country research station Rahangala at an elevation of 1300 m (4,200 ft).
Generally 20 tubers per variety were planted and daily records of the wilt performance were maintained. Readings later than 70-80 days after planting were often unreliable because the plants sometime died off due to late blight during the wet season or high temperatures ended the vegetation period prematurely during the dry - season.
47

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48

Page 38
TABILE 5.
RAIN FALL, DATA FOR RAHANGALA (average of 5 years)
Month Days Month Days
- r January 4. 13 July 4. 6 February 32 8 August 48 5 March 32 8 September 67 5 April 223 8 October 262 7 May 60 () November 220 2. June 28 5 December 5 13
Total 578 29
The Rahangala Station is located in the same climatic region and therefore has a similar weather pattern as Passara, as may be seen when comparing Table 5 with Table 2.
2. 2. l. Variety trials s
The trials comprised 92 varieties of which :
43 varieties were tested once
6 ஒ ஒ twice
32 ஒரு ஒரு ஒரு thirice
5 ஒ9 ஒ9 ... four times 6 ஒ9 ஒரு five times
The varieties which were tested twice or more times are given in Table 6, their tolerance to wilt is estimated on the basis of the number of days elapsing between the time of planting and the time that 50% of the plants show wilt symptoms. As in several trials severe late blight occurred before the plants were mature, this measure is more reliable than the total number of plants wilted (at harvest) as used for determining the tolerance of the varieties presented in
Table 3.
It can be seen from Table 6 that under the condi. tions of rather heavy soil infection at Rahangala 35 of the 42 varieties must be rated as poor to moderate. On account
49 |
 
 
 

of our experience this would mean that these varieties would probably also fail under similar conditions elsewhere. Of the remaining 7 varieties 3 are rated as moderate to good and 4 others as good to very good, among which are Lerche and Lori. These two varieties also showed some tolerance when tested at the other three locations (see Table 2 and 3), but their performance was poor when compared with that of such varieties as Ambassadeur and I. V. P. 654 which consistently showed a high degree of tolerance in these tests. The other 6 varieties (Dekama, Eigenheimer, Extase, Gineke, Irene, Mentor) common to both series of tests were, with the exception of Dekama, found to be poor to moderate performers in both cases.
MABILE 6.
Average wilt score of varieties tested twice or more times at Rahangala (determined on 40-80 tubers per variety)
Score of each variety is determined by its variation from the Average for all varieties of each trial on the basis of the number of days elapsing between time of planting and the time that half of the number of plants have becorne wilted:
() poor (more than 10% below average) I moderate (less than 10% below or above average) 2 good (more than 10% and less than 50% above average) 3 very good (more than 50% above average)
Variety S:COT"e Variety SCOe Variety ς OOI"θ
Agnes ().7 Epoka l,岛 sola 3. Arco () Eva 1.0 Lerche 2.7 (1.0) Arensa 1.0 Eigenheimer 1.0 (0.8) Lori 3.0 (0.5) Arka 2 Extase () (O) Magna 0.3 B. D. 2.5 Feldeslohn ().7 Maritta ().7 B. D. 7 沿.0 Fina () Mentor l. 3 (0) B. D. A. ().5 Flisak 1.8 Olympia 0.7 Cherokee () Franziska ().3 Patrones 1.7 Comtesse ().7 Gineke 0 (0.1) Pimpernel () Condea I.() Crata ().3 Poet 1.7 Cosima I.() Hansa () Realta 1.3 |Datura () Heiko ().7 Spartaan ..() Dekama 1.7 (0) Hessenkrone l. () Toradra ().7 Delos () rene ().3 (()) Wis .3
N.B. Figures between brackets represent the wilt score obtained at the other 3 locations (see table 3)
5()

Page 39
Taking into account the results obtained with the 8 varieties tested at Rahangala as well as at the other locations, it seems questionable whether any of the varieties tested at Rahangala possesses a sufficient degree of tolerance
to survive in wilt-infected soil, though it is not unlikely
that some could be cultivated economically under conditions
of light infection.
2. 2. 2. Influence of tuber source
With regard to the governmental potato project in Ceylon it is the practice to import yearly a certain amount of seed potatoes from abroad. These are multiplied two or three times at stations (at a high elevation) which are free of wilt and then issued for the production of consumption potatoes. It appears from the results of Il varieties which were grown both from local seed (comprising in total 400 tubers) - originating from a first multiplication at an elevation above 2000 m - and from imported seed (involving in total 300 tubers) that there was no difference between both groups with respect to their susceptibility to wilt or as to their general performance.
This is in accordance with results mentioned in para 2.1.3. which were obtained with first and second generation tubers propagated under conditions of wilt infection. Accordingly it seems quite certain that multiplying seed potatoes (up to two times) at a high elevation would not lead to undue degeneration.
2. 2. 3. Environmental influence
The climate at the Rahangala station shows two clear seasons: heavy rains when the N. E. monsoon starts in October to December. Then the weather becomes drier (but April is rainy) with a well defined dry season during the S. W. monsoon from June to September (see also Table 5). Since the trials were planted throughout the year it is possible to ascertain the effect of climatic conditions on the performance of the varieties with respect to wilt.
Altogether 14 trials could be used for comparison: the average results of each trial, based on the average number of days till 50% of the plants had wilted, have been entered in Table 7.
5.
 

TABLE .
Seasonal influence on the tolerance to wilt at Rahangala expressed by the average (for all varieties per trial) number of days elapsing between the time of planting and the time that half the number of plants have become wilted.
Series 1 : 3 trials with 19 varieties (380 tubers per trial)
ஒத 2 : 2 . 99 9 ஆகு (180 ஆ% 99 وه (
% :3 : 3 , , ... 10 ஒரு (200 தகு ஒ9 .وو (
ஒத் A : 3 ஒ% ஒத 4. ஒ8 ( 80 ஒரு 99 ஒ% )
99 5 3 9% ஜூ 4. - ஒ% ( 80 ஒ9 ஒ9 ጓ % )
Series Month No. of Series Month of No. of
planting days planting days
June 1962 37.1 I January 1963 4.2 October 1962 424. ༡ க 43.4 2 December 1962 5.9 5 March 1963 岛7.0
3 ஒரு 59.8 3 September 1963 59.5 4. ஒரு 54.8 4 ஒரு 57.5 4. த9 60.8 5 ஒ 68.() 3 December 1963 49.9
5 46.3
It can be seen from Table 7 that the planting season affects the length of the period that half the plants become wilted. This can be derived from the fact that these periods are of the same order for different trials planted in the same month, but considerably differ from those resulting from planting in another month.
ܐܸܠܨܬܐ
For instance, planting in June and October 1962 caused half the plants to wilt in a shorter time than planting in December 1962, especially when the two plantings of series 2 are compared which differ by ten days. Likewise planting in January and March 1963 showed 50% wilting up to thirteen days earlier than planting in September 1963. Series 5 shows this marked difference of the two planting seasons clearly, and the wilting time for the planting in December 1963 is in between. Series 3 can be used for a comparison between planting in September and December 1963 which shows the same tendency with a difference of
ten days as described for series 5.
52

Page 40
it can be further seen that the results for December planting in 1962 and 1963 are not similar, especially by considering series 3 where the wilting time for 50% of the plants differs by ten days.
Although planting at different times causes significant differences, these are not so clearly related to a particular season as was the case with the trials carried out at St. Coombs and Elantane (Fig. 5). There seems to be a tendency that the rate of wilting is accelerated when planting is followed by rising temperatures or is done at times of drought when it is hot. On the other hand, the results are not consistent, when planting is carried out during wet weather with lower temperatures. It seems likely that the picture is not clear due to the interaction between rainfall and temperature with respect to the activity of the pathogen.
3. YIELD TRIALS ON TEA LAND
Nine trials were carried out in tea land on a larger scale than those concerned with the testing for wilt resistance; two of these were done in infected gardens the others on a number of estates in soils which had carried tea for some tens of years previously and which were assumed to be free of Wilt. These latter trials served a double purpose; firstly to test the yield performance of several potato varieties under conditions where their relative susceptibility to wilt would be of little importance, secondly to ascertain whether potato cultivation following the uprooting of the old tea and prior to replanting (usually preceded by soil reconditioning with Guatamala grass for one or two years) would be an economic proposition.
3. I. Variety trials
The different locations and the data' concerning the trials are given in Table 8.
In addition to the data given in Table 8 it may be
mentioned that half the plots of trials 1, 2, and 4 were sprayed with a zinc carbamate preparation, the others with
colloidal copper.
The results of the 6 field trials (of which the first four were carried out simultaneously) which have the same
53

扈
TABLE 8.
Date relevant to the yield trials carried out at five locations
Trial Location cultivated No. of No. of tubers Period of Source of
O. in var. per variety trial tubers
| St. Coombs 140{) ml) 9 2 x 35 March une 1961 Netherlands 2 Conakel le 1050 m L) 9 2 x 35 ... do . do . 3 Hugoland 900 m!) 9 2x35 - do - - do - 4. Han tanae 750 ml) 9 2 x 35 - do - do - 5 St. Coombs l400 ml) 9 2 x 200 Oct. 61-Jan. 62 Test (1) 6 Matakelle 1400 ml) 9 2 x 100 May - Aug. 1962 Test (5) 7 St. Coontos 400 m2) 5 8 x 40 Oct. 61-Jan. 62 Test (1) 8 St. Coombs 400 m3 6 4 x () - dlo - list gen. S. C. *** 9 St. Coombs 400 m 4) { 6 x 14 May - Aug. 1962 2nd gen. S. U.**
1. tea land from which the old tea had been uprooted 1-3 months previously 2. 8 vegetable gardens at St. Coombs, wilt infected: 3. infected garden plot at St. Coombs: 4. tea land which had been under grass for 20 months after the uprooting
of the tea.
* exclusive of seed tubers of Gineke and Tedris which came from a govern
ment potato farm in Ceylon at 2000 m.
* seed tubers once or twice multiplied in tea and at St. Coombs.
potato varieties in common are given in Table 9: the yields refer to healthy tubers only. These are given in tons per acre in spite of the fact that the number of tubers planted in these trials was sometimes not very high. Any other form of presenting the yield figures makes it difficult to understand the level of yield potentialities, though the authors are quite aware of the danger in converting yield figures from relatively small areas to tons per acre. On the other hand, it should be borne in mind that all trials were replicated and by considering each trial as a whole the number of tubers planted is large enough to obtain a reliable impression of the yield potential.
It will be seen from Table 9 that the performance of the different varieties varied with the location. The Matakelle trial gave on an average the lowest yield because of the unfavourable weather conditions (SW-monsoon predominantly rainy) causing severe late blight infection; the
54.

Page 41
The yield of 9 potato varieties in tons peracre on five tea
=,
TẢ BÍLE
9.
5. 7] 7.95 3. 35 3.70 4. 20 6. 45
5.16
6. 69
Varieties|23 St. Coombs (Gonak elle
Ambassadeur7. 239.505. 47 Eigenheimer7.82| 2.857.84 Extase7. 14.9. 437.2] {{Çineke8. 289. 105. 66 Luetor6.367.41 5. 29 Noordeling5. 86| 7.14 6. 19 Profijt8. 699.745. 12 Tedria6. 7]8. 457.86 Voran9.5010. 697. 23 Average7. 519.306.43 Sign, diff, at P - 0.05%1. 68
5
estates
6
Hugoland Hantane St. Coombs Matakella
6. 474.70 . 6. 432.72 6. 252.94 7.993.27 6. 432.53 4. 622. 27 7.414. 92 해 3%5. 7] 7. 432.05 6. 693. 46 1.44 0.76
|-
1–6
Average %
6.5] 7. 60 6.03 6.34 5. 38 5. 42 6.84 7. 10
(100), (117) ( 93) ( 97) ( 82) ( 83) (105) (109)
 

(*)
average yields for the two St. Coombs trials in 1961 and
1962 were similar although the areas and seasons differed;
the average yield was highest at Gonakelle estate. Visually no wilt symptoms were observed in the plants at any of the locations. A fairly high percentage of tubers were found to be rotted at harvest in the trials at Hugoland and Hantane estate, which depressed the yield considerably: this was not observed at the other locations. It is fairly certain that the rotting of the tubers in the soil was indirectly related to the delay in harvesting causing tuber infection by Phytophthora infestans. Rotting viz, was significantly reduced by spraying the plants with a zinc carbamate compound as compared with the spraying with colloidal copper which, as was found recently (4), is less effective in late blight control. The yields of plants sprayed with zinc carbamate in trials I and 2 on St. Coombs and Conakelle estate (where no rotting occurred) were also significantly higher than those of plants sprayed with colloidal copper. It can be further derived from Table 9 that Luctor and Noordeling were on the whole poor performers at all locations. Eigenheimer and Voran gave on an average the highest yields: their yields at Matakelle were low. Ambassadeur was one of the best varieties at Matakelle also on account of its resistance to late blight, its performance at the other locations was approximately average. Profijt and Tedria were on the whole slightly above average, while Gineke and Extase were slightly below average.
The yields of the remaining 3 trials are presented in Table I0, from which Noordeling appears again to be a poor yielder; this was also true for Gelderse Rode and Zeeburger. Plants of these three varieties were not very vigorous and formed a smaller number of stems than e. g. Eigenheimer and Hilla which gave the highest yields. Ambassadeur and Tedria gave an average yield in one trial and yielded above average in the other, both appeared rather resistant to late blight. The former showed also a much higher tolerance to wilt than the latter in trial 7. I. V. P. 654 performed badly under monsoonal conditions, mainly due to its susceptibility to late blight. Gineke gave only an average yield in the SW-monsoon trial at St. Coombs, as in the similar trial at Matakelle: Woran was slightly below average in the garden trial. Accordingly, it
56 :

Page 42
appears that most varieties yielded more than 5 tons per
acre. Even assuming the fact that the yields of trials are about 20% higher than those obtainable on a commercial scale, a minimum yield of 4 tons/acre is still a profitable result. From other sources it is known that a yield of 2 tons/acre will cover all costs of cultivation including seed. spraying material, fertilizer and field operations provided the guaranteed price of 25 cts. per pound is maintained. These trials strongly suggest that planting of a short term crop, like potato, in uprooted tea land prior to soil recondi. tioning with Guatemala grass is able to reduce the costs of the unprofitable period before replanting with high yielding tea clones. Such cultivation has furthermore the advantage to get the soil in good condition and to control weed growth.
TABLE II ().
The yield of 10 potato varieties (in tons per acre) in two trials in gardens and one in tea land which had been in grass for 20 months
7 8 9 garden garden tea land St. Coombs St. Coombs St. Coombs Varieties SW/NIE ’6I-’62 SW/INE ’6I.”62 SW - || 962
yield yield yield
Ambassadeur (8) 7.86 5, 60 - Eigenheimer (8) 9.3 7. 73 6.23 Noordeling (9) 4.03 4.42 - Tedria (47) 6, 47 - 5.2. W oran (15) 5. 7 - - Hilla - 7.95 5.64. I.V.P. 654. - 5.99" 2.77 Gelderse Rode - 3.42 2.83 Gineke - - 4. () 5 Zeeburger - - 3。22
Average 6, 64. 5.86 4. 27 Sign, diff. I, 70 ... 6 0.96
at 5% level
* between brackets to wilted plants
57

4. DISCUSSION AND CONCLUSIONS
Hundreds of commercial potato varieties and selections have been tested for their resistance to Pseudomonas solanacearum under tropical and sub-tropical conditions in Australia (8, 9), Brazil (II), Ceylon (l, 2, 3, 4, & 22), India (10), Java (13. 20, 21, 24), Portugal (12), South Africa (24) and the United States of America (6, 7, II, 14, 15). However, not one was found to be immune or resistant, though there are differences in tolerance, e.g. as measured by the time elapsing between planting and first infection. The most recent and extensive review of the available infor. mation is given by Kelman (I.2). Both from this review and the investigations of the above mentioned authors it appears clearly that the performance of a given variety greatly depends on the location where it is tested. It may be found tolerant in one place but susceptible in another one, in either the same country or in different countries. Since up till now the few investigations carried out on this subject (8, 9, 12) have not ans wered the question whether or not different strains or strains differing in their activity exist, the conclusion is allowed that environmental conditions have a greater effect on the performance of varieties than their inherently determined tolerance or susceptibility. It seems superfluous, therefore, to compare all the many varieties common to our tests and those of others as they confirm the general picture of a greatly varying tolerance at various places.
As an example may serve the varieties Sebago and Prisca which have been found fairly tolerant by Eddins (6) and Nielsen and Haynes (15) respectively, but which appeared susceptible in our tests. Of interest are the varieties Green Mountain and Katahdin which have been frequently mentioned as relatively tolerant (1, 6, 15). Nielsen and Haynes (15) found both varieties as highly infected as others, but infection occurred in a later stage, this was also observed in our trials. This behaviour is typical for varieties which may be called relatively tolerant. In our trials the majority of varieties appeared to break down early in the growing period so that no tubers are formed. A small minority withstood wilt infection until much later or even until harvest time and thus was able to form tubers:
58

Page 43
varieties such as I. V. P. 654, Hilla and Ambassadeur showed a high degree of tolerance in that respect. It is worthy of note that the yield was found to be inversely proportional to the percentage of plants infected at harvest time.
Accordingly in tests such as ours done in heavily infected soil, it is possible to screen the varieties locally for their degree of tolerance, particularly as to the percentage of plants which reach maturity uninfected. As long as this percentage is relatively high or the break-down of plants occurs relatively late as compared with that of other varieties, it may be assumed that such varieties are potentially able to produce economic yields in land which is only little infected. Such varieties are obviously preferable for potato cultivation to those which in the same tests show a very much smaller degree of tolerance. Although there may be prospects to breed resistant varieties; e.g. by making use of primitive forms of potatoes, the results so far obtained do not seem promising (15, 19), Therefore, until such a time that the plant breeders may become more successful, the continued search for varieties which are "adapted to a particular area offers the only practical
approach.
With respect to the condition of tubers harvested (visually healthy) from plants grown in infected soil, no appreciable loss will occur if they are used for consumption within a short space of time. If such tubers are stored the infected tubers will start rotting sooner or later depending on the temperature. As the length of the dormant phase as well as the rate of development of the bacterium in the tubers are positively related to temperature, the tubers will generally rot before they sprout and are thus eliminated from planting. Accordingly, as also shown by our trials, carefully selected tubers from contaminated sources produce (in wilt infected soil) as well as tubers from uncontaminated sources. However, the use of such tubers involves the risk of contamination of Wilt-free areas, while it is costly due to losses during storage and laborious because
regular elimination of rotted tubers is necessary. It is much
wiser and simpler to use seeds produced in wilt-free areas. The observations indicate that potatoes multiplied (once or twice) in Ceylon at a high elevation (above 2000 m) are
59

not subject to degeneration and perform as well as tubers directly imported from abroad.
The planting of tuber halves in infected soil had no effect on subsequent plant infection, presumably because infection through the eyes and other organs of the plant occurs as easily as through the damaged part. This appeared to be the case in heavily infected soil, but it is possible that in little infected soil injured tubers may be infected faster than healthy tubers. Besides the fact that the cutting operation itself may transmit the pathogen, it should also be borne in mind that tuber halves give lower yields than whole tubers, cutting therefore should be avoided.
Environmental conditions appear to have a dominant effect on the level of wilt infection. This is particularly true as regards the temperature which, as has been reported by many investigators, determines the activity of the bacterium to a very large extent. The decrease of the infection of potato plants with increasing elevations and the absence of it at the highest elevations, is no doubt a temperature effect. Our observations also showed that much less infec. tion occurs in the cooler season than in the hotter part of the year which confirms similar findings of Van Eek and Thung (21) in Java. These observations point likewise to a temperature effect, but as nothing is known of the interaction between temperature and rainfall, it may not be correct to explain these seasonal differences on account of temperature differences alone. In any case it is clear that for economic potato cultivation the cooler season, avoiding the rainiest part of it (to avoid late blight 4) and high elevations are preferable to the warmer season and lower altitudes.
The previous cropping history of the land also constitutes an environmental factor. The garden trials showed that previous cultivation with crops subject to wilt infection, such as Solanaceous crops (but also banana), cause a level of wilt incidence which was much higher than in land previously grown in grass. Observations on up-country potato farms in Ceylon showed that fields causing a notable infection became practically wilt-free after 2 years of fallow during which a natural grass vegetation established itself.
Land cultivated with rice was also found to be relatively
60

Page 44
free of wilt (2, 19). Accordingly when carrying out crop rotation, an essential feature of successful potato cultivation also on other grounds, the cultivator is advised to use plants belonging to the graminaceous family as these can reduce the incidence of bacterial wilt.
Tea appears to offer the same advantage, as can be derived from the success of extensive yield trials in tea land and in which at elevations above 1000 m no wilt occurred. These trials showed that it is quite possible to raise an economic potato crop in up-country tea areas after the uprooting of the old seedling tea and prior to soil-reconditioning with grass which precedes replanting.
The majority of the varieties tested were able to yield more than 5 tons per acre. However, the yield seemed to be lower at lower altitudes (higher temperature), so that generally cultivation at elevations well above 1000 m should be preferred, while it is also important to choose the correct planting season. Accordingly, as mentioned before (23), the possibility of potato cultivation deserves the attention of up-country tea estates, though it is fully realised that its success is also greatly dependent on outside factors, such as the availability of healthy seed, an efficient distribution system, advise, etc.
5. SUMMARY
422 potato varieties and selections were tested for their tolerance to wilt in the hilly regions of Ceylon. More than 300 of these were tested first at 1400 m altitude of which about 85% were rejected after this test, the remaining varieties were retested, partly also at two other locations at 1050 and 750 m altitude: 92 varieties were tested at an altitude of 1300 m, 49, varieties of these were tested two or more times at this location. Four varieties Ambassadeur, Gelderse Rode, Hilla and IVP 654 showed superior tolerance in 8-10 tests producing a good crop in moderately to heavily infested soil, two other varieties showed a fair tolerance. The tolerance reaction was observed to involve different plant responses to the disease and is generally characterized by a slower development of the disease symptoms (resulting in a smaller proportion of infected plants at harvest), the infected plants succumb
61

in Ore slowly and fewer tubers become infected: the loss of yield was proportional to the percentage of plants infected.
Both the literature and our results indicate that immunity or even resistance among the commercial potato varieties does not exist, but there is a certain tolerance among varieties indicated by the speed of infection. Varieties which are infected late are able to produce a profitable amount of tubers in spite of being not entirely free from the disease.
The performance of contaminated seed tubers, if selected healthy, equalled that of uncontaminated tubers planted in infected soil; cutting of the tubers into halves neither influenced subsequent infection, but decreased yield.
The success of potato cultivation, as measured by the degree of disease incidence was found to depend to a large extent on the weather pattern of the growing season and the altitude of the location. Tea land at up-country elevations appeared to offer opportunities for commercial potato growing, particularly as it appeared to be free of wilt.
6. ACKNOWLEDGEMENTS
Our sincere thanks ale due to Mr. M. Piyasena for his conscientious supervision of the field trials and to M/s. D. D. Kroon and H. B. Ratnayake, Officers-in-Charge of the substations Passara and Hantane as well as to Mr. S. N. de S. Seneviratne, Research Officer-in-Charge, Agriculcultural Research Station Rahangala.
7. REFERENCES
I. Administration Report of the Director of Agriculture
for 1962-63, p. 92, Colombo (1964).
2. Abeygunevardena D. Y. W. and R. A. Wijesooriya, Methods
of potato seed production in Ceylon. Trop. Agricst. CXVI, 131-139, (1960)
3. Abeygunewardena D. V. W. and A. A. P. Siriwardena, Disease hazards in potato cultivation. II. Brown rot or
bacterial Wilt caused by Pseudomonas solanacea rum. Trop. Agricst. CXVII, 221-225, (1961)
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Caesar K. and S. Ganesan, Control of late blight in potatoes. Trop. Agricst. CXIX, 5–24, (1963)
Davidson H. F., Bacterial wilt of solanacea.ous crops (Dept. notes) Trop. Agricst. XCI 257-259, (1935)
Eddins, A. H. Brown rot of Irish potatoes and its control.
A gr. Exp. Sta. Florida, Tech. Bull. 299, p. 43, (1936)
Eddins, A. H. Investigations and control of brown rot
of potatoes and related plants. Agr. Exp. Sta. Florida, Ann. Rep. for 1945, p. 109
Harrison, D. E. and H. Freeman, Bacterial wilt of potatoes.
I. Field symptoms of the disease and studies on the
causal organism, Pseudomonas solanacearum var.
asiaticum.
().
II.
2.
Austral. J. Agri. Res. 12, 854-87 I, (1961)
Harrison, D. E. and H. Freeman, Bacterial wilt of potatoes. II. Serological relationship of two strains of P. solanacearum and a culture of Corynebacterium sepe
donicum. Austral. J. Agri. Res. 12, 872-877. (1961)
Hingorani, M. K., P. P. Metha and N. J. Singh, Bacterial brown rot of potatoes in India.
Ind. Phytopath. 9, 67—71 (1956)
Kelman, A., The bacterial wilt caused by Pseudomonas solanacearum. A literature review and bibliography.
North Carolina Agr. Exp. Sta. Techn. Bul. 99, (1953)
Moraes, A. de M. Uma bacteriosa vasculas de bacteria
(Bacterium solanacearum E. F. Smith).
13.
4.
Agron. Lusit. (Portugal) 9, 277-328, (1947)
Muller, H. R. A., de aardappelsituatie op Java als gevolg van het optreden van enige nieuwe ziekten.
Landbouw 13, 285-313, (1937)
Nielsen L. W. and F. L. Haynes, Control of southern
bacterial wilt. Potato Handbook, Pot. Ass, of America,
63
Vol. II, 47-51, (1957)
|

5.
6.
7.
8.
9.
20.
21.
22.
23.
Nielsen. L. W. and F. L. Haynes, Resistance in Solanum tuberosum to Pseudomonas solanacearum. Am. Pot. J. 37, 260-267. (1960)
Park, M. Report of the Mycological Division. Ceylon Dept. Agr. Techn. Rep. 1928-29, p. 1-6
Petch. T. Miscellaneas Trop. Agricst. XV, 521, (1909)
Pushkarnath, Report on the potato development project in Ceylon. Trop. Agricst. CXVI, 73-12°, (1960)
Thung, T. H., Potato diseases and hybridisation. Phytopat. 37, 373-381, (1947)
Van der Goot P, Overzicht der voornaamste ziekten van het aardappelgewas op Java. Inst. voor Plantenziekton (Buitenzorg), Bull. 18, p. 42, (1924)
Van Eek, Th. and T. H. Thurg, Resultaten van onderzoekingen omtrent aardappelziekten op Java.
Landbouw (Bogor, Java) 22, 305—346, (1950)
Visser, T. Potato cultivation on estates. Tea Quart of Ceylon 32, 55, (1961)
Wager V. A., Bakteriese verwelksiekte bij aartappels. Boerderij in Suid-Africa 20, 501-507, (1945)
Wellensiek, S. J. De vatbaarheid van 32 geimporteerde aardappelrassen. Korte Mededelingen Inst. voor Plantenziekten (Buitenzorg) 16, p. 5, (1931)
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THE EFFECT OF WATER TEMPERATURE ON RICE (ORYZA SATIVA L.) AND ITS INFLUENCE ON COLD TO LERANCE AND DISEASE RESISTANCE.
W, HERAT
PPROXIMATELY 20,000 acres of rice are affected annually by low temperatures in the upcountry of Ceylon. These areas are mostly confined to Nuwara Eliya and Bandarawela districts. In Pussellawa, a minimum temperature of 17 C has been reported frequently (7) Water temperatures tend to be still lower at higher elevations. Most of the rice varieties grown in these areas are unable to withstand the low water and soil temperatures and as a result their seedling establishment subsequent growth and yield are seriously affected. Hence, the testing of local and introduced varieties for cold tolerance is of great importance to the cultivator in these districts.
Matsuo (9) reported that a water temperature of 40. to 43° C is the maximum and 13° C is the minimum requirement for rice plant growth. Chapman and Peterson (3) found that water temperature in the range of 25°C to 30° C. is the most favourable for seedling establishment.
The present study was made to determine the effect of both low and high water temperatures on the behaviour of rice plants, by observing the changes in the develop. ment and growth of certain morphological characters. A further attempt is made to assess the importance of these characters in disease resistance (Blast and Helminthosporium).
Certain Californian varieties have been found to be more cold water tolerant than other varieties: (Ormrod and Bunter, (11) Herath, (6).) Temperature is one of several ecological factors controlling plant growth and it is hard to study its effect separately, under normal conditions, due to
65

the interaction of other ecological factors. However, it has been possible to study the effect of water temperature under controlled environmental conditions.
The geographico-ecological studies of Sakei revealed that the homeostatic properties or wider adaptability of H.A. was greater than Murungakayan 302. These results in turn agreed with stomatal development patterns studied by Ariyanayagam (2). This supports the fact that inferences can be made regarding the adaptability of varieties to different environmental conditions by studying the development of morphological characters in rice.
Cobb (4) was the first to report that resistance to rust of wheat was correlated to certain morphological characters. Since then several other workers have found that morphological characters such as the amount of sclerenchyma to Collenchyma was important in the resistance of wheat to Puccinia graminis. Plants with higher percentage of crude fibre aud potatoes with thicker skin are some of the other disease-resistant characters of importance. Therefore, as indicated by Adyanthaya and Rangaswami (1) and Suzuki (12) the study of silica deposition and the development of stomata on the leaf lamina of rice are of great importance to the pathologist.
MATER ALS AND METHODS
A constant temperature thermost at regulated water bath in a greenhouse was used for the two experiments. Size of the tank was 8' x 4' x . . It was found suitable for covering the pots with an adequate level of water. The tank was partitioned into three compartments. Water temperatures in these compartments were maintained at 16° C. 24° C and 32° C respectively. Light requirements were supplied by means of daylight and a bank of cool white fluorescent lights. The air temperature was recorded by means of a Tempscribe thermograph and the water temperature was recorded by a three point thermograph.
One gallon capacity plastic pots were partially filled with seven pounds of silty clay loam soil. The pots had a space of five inches from the soil surface to the brim, so that when submerged the total depth of water in the
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pots was about six inches. (Five inches in the pot and one inch in the tank). The usual rate of fertilizer was applied to all the pots. Seeds were sown into pots under submerged condition.
In experiment ... two pots representing cold tolerant varieties aud non-tolerant varieties were sown with Caloro and Bluebonnet at each of the three temperatures (16 °. 24, 32° C). From the fourteenth day onwards two plants from each pot were removed every week and the most recent leaves were used for this study. Sections of leaves, two centimeters in length were cut from the tip of the leaf blade (after removing a centimeter from the top). These were then partially macerated, stained and mounted before observing under the microscope. Silica crystals were designated from “A” to “E” for convenience of study. (Plates I a and I b) A Leitz, Wetzler microscope with an orthomat attachment for automatic control was used for the photographs, and they were taken at x5000 magnification.
In the second experiment four varieties representing both tolerant (caloro, callrose) and non-tderant (Bluebonnet, Texas Patna), Were grown. A completely randomized design with four varieties and three replicates was used. Weekly sampling was done by removing an entire pot. Impressions of stomata from leaf blades were taken onto plastic cover slips. This was accomplished by applying acetone on the leaf and placing the cover slip on the leaf and holding with pressure for about a minute. The size and number of stomata were determined by the use of an occular micrometer under x300 magnification. Length and breadth of stomata were measured and converted to an area assuming an ellipse shape. Photographs were taken in the manner
described above. (Plate II a)
ܛ . RESULTS
Table I and 2 give the data for both stomata number . and stomata size on the upper surface of the leaf lamina. The overall effect of temperatures on the size of stomata
was quite variable. There was a significant interaction at all weeks apparently because of different variety behaviour each week. In general, leaves from the 24° C treatment had the largest stomata at the first week and 16° C had
67
 
 
 

the largest at the third week. The smallest number of stomata was at 16° C followed by the other two temperatures: 24° and 32° C in the order of increase Table I. The amount of increase at higher temperatures depended on the Week of measurement. The differences in the effect of temperature on the number of stomata were highly significant during the full period of investigation. A temperature x variety interaction was perceptible for two weeks for stomata numbers but this was absent at the third week. The stomata numbers at low temperature was usually greater in non-tolerant varieties, while at higher temperatures there was a tendency for all varieties to be about equal.
TABLE 1.
Effect of variety, water temperature, and time of measurement on the count of stomata on the upper surface of the leaf lamina in rice seedlings.
No. of stomata per square .0479 sq, mm.
Varieties
Texas Calrose Bluebonnet Caloro Average
Patna Temp. C. Week I.
I6 6.00 5.50 7.00 5.50 6. ()() 24. 8.50 5.00 7.50 5.00 6.50 32 A. OO 15.50 4, 5 () 3.5 () I.A., 37 Average 9.5 () 8.66 9.66 8. () ()
TxV* T* V ns. Week 2. I6 6.5 () 5.50 7. () () 3.50 5, 62
24, 2 . () () II. () () (). 5 () 3. ()() I. 62 32 3.50 I6.00 3.50 2.00 13.75
Average 10.66 0.83 丑0.33 9.50
TxV* T** V ns.
Week 3.
I6 5. 5 () 3.50 8.50 8,50 6.50
24. 8,50 2. () () (). O() 2.5 () ().75 32 A. () () 4. () () II - 5(0) 15.00 3.62 Average 9.33 9.83 (). OO 2.00 TxV ns. T** V ns.
Note: Impressions taken from the leaf tip of the most recent full leaf.
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ABLE 2.
Effect of variety, water, temperature, and time of measure. ment on the stomata size of the upper surface of the leaf lamina in rice seedlings. ( u")*
Varieties
Texas Cal rose Bluebonnet Caloro Average Patna Temp. C. Week I.
6 28 () }3() 26() 8. () 420 24. 37 () 54() 57() 44() 45 () $2 22 () 35() 29 () 280 28 () Average 29() A. () 34() 5 () Tx V* T ns. V ns.
Week 2. 6 284) 2. () 25() 58 () 33 () 24. 34() 53 () 29() 360 38() 32 32 () 270 28 () 280 29() Average 3. () 34() 27() A. ()
Tx V * T ns. V ns. Week 3. 6 38) 99 () 22 () 43() 5()() 24. 3() () 320 23 () 29() 28 () $2 35() 380 25() 30() 32 () Average 340 57() 230 34()
TxV * T ns. V ns. Note: from impressions taken from the leaf tip of the most recent
full leaf. * from A- it. Where a = length b = breadth
The temperature effect on silica crystal formation was clearly shown by the occurrence of more types and numbers of crystals at higher temperatures (Table 3). There was no appreciable difference between the two varieties in numbers, type, and length of crystals formed at all temperatures. At 32° C. at least four crystal types were deposited and at 24° C three or more types were formed, at 16° C the intensity of silica deposition was considerably lower. Crystals of “A” and “D” types were not observed at 16° C. The number of “D” and “C” were also extremely low. Only crystal type “E” was always present.
69

PLATE la-A, D & E types of Crystals.
PLATE I b-B, C & E types of Crystals.
PLATE 2a –Stomata on the upper
surface of Rice Leaf.

Page 49
f
 
 

TABLE 3 A.
variety, water temperature, and time of vation on the intensity and the formation of “A” and “B” type silica crystals on the leaf lamina of rice seedlings.
A = absent P = present F = few VF = very few
“A” Type
Week 2 Bluebonnet Caloro Week 3 Bluebonnet Caloro
이() 이C Temp. 16 A A. Temp. 16 A A.
24 F WF 24. A WF
32 P P 32 P WF
Week 4. Bluebonnet Caloro
OC Temp. 16 A A.
24. A A.
32 A. A.
TABLE 3 B.
"В" Type
Week 2 Bluebonnet (Caloro Week 3 Bluebonnet Caloro
P() 이() Temp. 16 F A. Temp. 16 F A. 24 F F 24. F F 32 P P 32 P
Week 4 Bluebonnet Caloro
이C Temp. 16 F A. 24 F F
32 P VF
Crystal type **C. showed an equal length for all temperatures at the end of three weeks. However, in general, Caloro had larger crystals than Bluebonnet. “D” crystals had a greater length at 24° C at the end of four weeks. There was a slight increase in length in Caloro, compared with Bluebonnet. When the number of crystals of “E” type per 066 mm. linear distance was measured at different temperatures, it was observed that there was a slight tendency
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for a greater number to occur at higher temperatures. Similar to stomata, the nnmber observed for Bluebonnet (Southern Variety) was greater than Caloro (Califonia Variety). and the size of crystal was found to be greater in caloro than in Bluebonnet.
DISCUSSION
According to Eckerson (5) variation in number and size of stomata occurs within species as well as within varieties, when grown under different environmental conditions. It is believed that this variation is more obvious when the growing conditions are non-optimal, as indicated in the present results. At higher temperatures of 24° C and 32° C. the stomatal development pattern was somewhat similar. On the other hand when they were grown at a sub-optimal temperature of 16° C they tended to respond differently. Non-tolerant varieties had more stomata per unit area of leaf opposed to that obtained in tolerant varieties.
From the results of previous investigations carried out by the author and other workers with California and other southern varieties, it was revealed that the former was more cold tolerant than the latter. Hence it was possible to infer from these results that the reduction in the number of stonata in cold tolerant varieties is an adaptive device to overcome the detrimental effect of cold temperatures. This ability of certain varieties to regulate the differentiation of cells to stomata in this instance, in response to the different external conditions is limited in non-tolerant varieties. Therefore it is believed that nontolerant varieties do not show an appreciable difference in the number of stomata per unit area of leaf whether grown at low temperatures or at high temperatures, to the same degree as tolerant varieties. In other words the range of adaptability is greater in tolerant varieties than in non-tolerant varieties.
The type of silica crystals formed on the leaf lamina was observed to be consistent with species as reported by Metcalfe (10). In this study at least five different types of Oryza crystals were seen. The number of types and the size of crystals varied at different temperatures. The intensity of silica deposition was greater at 32° C than at 16° C.
7.
ད།
 
 
 
 

indicating that a change in the environment can bring about a change in the normal rate of silica deposition. This morphological character can also be used as a tool to determine the degree of response to varying temperatures for different rice varieties. However a comparative study of varieties in respect to this aspect was not investigated in the present study.
Silica deposition is found to be more important in the study of disease resistance. The thickness of the outer wall and the silicated outer most layer of the epidermal cell and stomata, larger number of silicated short cells Suzuki (10), are some of the importart factors in disease resistance, mainly because of the ability of plants with such qualities to resist penetration of Piricularia Oryzae and Helminthosporium Oryzae. It could therefore be stated that when rice plants are grown at temperatures closer to optimal their tendency is for greater silicification which in turn serve as an important feature of disease resistance.
Suzuki (10) stated that the number and size of stomata does not seem to he significantly related to the susceptibility of the plant to diseases. Hursh (8) also reported from the results of his studies on the resistance of wheat to puccinia graminis tritici, that the size and number of stomata cannot be considered important in influencing the entrance of the germ tubes. However the stomatal movement may have some influence on the entrance of germ tubes according to the same author.
In conclusion it is conceived that the study of the behavior of stomata on the leaf blade of rice is important from an adaptational aspect and the deposition of silica crystals is important from a disease resistance aspect, and both studies provide a wide scope for future research, particularly with our local varieties.
BBLOGRAPHY.
l. Adyanthaya, N. R., and Rangas uvami, G. “Distribution of silica in relation to Blast disease in rice'. Madras Agric.
Jour. XXX IX, pp 198-199 — 1952.
Ariyanayagam, D. V. --Genotype- Environment interaction, Symposium on rice production and the environment. 1961.
2.
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().
II.
2.
mental factors on the susceptibility of the rice plant to
Chapman, A. L. and Peterson, M. I. “The seedling establishment of rice under water in relation to temperature and
dissolved oxygen". Crop Science. 2: 391-395 – 1962.
Cobb, N. A. “Contribution to an economic knowledge of the Australian rustsʼ. Agric. Gaz. N. S. Wales I HI, l02—l8l. Abs. Madras Journal of Agric. Vol. XXXIX. 198-1952.
Eckerson. S. H. “The number and size of the stonata’. Bot, (Gaz. 46: 22I—224 — 1908.
Herati, H. M. W. “Growth and development of rice seedlings as influenced by water temperature”. Un published - Master's Thesis, University of British Columbia, 1964.
Hineda, M. “Research works for rice cultivation in Ceylon". Overseas Technical Cooperation Agency, Booklet 48-57 1964.
Hursh, C. R. “Morphological and physiological studies on the resistance of wheat to Puccinia gramini tritici". Journal of Agric. Res. XXVII. 381-409, Abs, Madras Agric. Jour. Vol. XXXIX, pp 198-199 — 1952.
Matsuo, Takane. “Rice culture in Japan'. Ministry of Agriculture and Forestry, Japanese Govt. Tokyo. 128 pp 1957.
Metcalfe, C. R. “Anatomy of the monocotyledons, I. Gramineae” Clarendon Press, Oxford, 731 pp 1960.
Ormrod, D. P. and Banter, W. A. Jr. “The evaluation of rice varieties for cold water tolerance'. Agron. Jour. 53:
卫33一]84,一 1961。
Suzuki, H. Studies on the influence of some environ
Blast and Helminthosporium diseases and on the
Anatomical characters of the plant'. Jour. Coll. Agric. Vol. XIII, No. 3, pp. 235-275 - 1935.
ACKNOWLEDGEMENTS.
My thanks are due to Dr. D. P. Ormrod, Associate
Professor, Division of Plant Science, University of British Columbia, under whose supervision this project was undertaken.

PEASANT AGRICULTURE IN CEY LON
P, C. BANSIL
OF the total geographical area of the Island (16.2 million acres) nearly ird constitutes the Wet Zone and the balance is Dry Zone. The present extent of cultivated area is only of the order of 3.8 million acres and the total extent said to be available for cultivation is roughly 6.5 million acres. This means that the total extent of land available for further exploitation is about 3 million acres. It would he interesting to note that out of the 3.8 million acres of the cultivated area as much as 2.8 million acres lies in the Wet Zone where agriculture is devoted mainly to the growing of plantation crops, notably, tea, rubber, coconut, papaw, cinnamon, pepper and spices. The total area cultivated in the Dry Zone is thus hardly of the order of 1.0 million acres. With the exception of the Jaffna Peninsula, where the standard of cultivation is comparatively high and a few scattered colonisation schemes in which rice production has been commercialised, agriculture in the Dry Zone is generally of the subsistence type. Rice is cultivated in the irrigable lowlands, while gingelly, gourds, cowpeas, grains and chillies are grown on the unirrigable land according to the traditional chena system which has survived from the time of the Sinhalese Kings.
The resources of the Wet Zone of Ceylon have practically been fully exploited and the density of population is very high. Table I will show that the population density in the Wet Zone has increased from 682 per square mile in 1946 to 810 per square mile in 1953 while the corresponding figures for the Dry Zone are 81 and 108. Latest data are not yet available. The position has in any case become Worse.
The total area of about 3 million acres available for cultivation lies in the Dry Zone. Since the development of this land is closely linked with the availability of irrigation
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TABLE II. -
Distribution of Land, Population and Cultivation
Ceylon Wet Zone Dry Zone
Land Area
Thousand sq. miles 25. () 7.7 7.3 million acres I6.2 4.9 III, 3 Population
1946 illi 6.66 5.25 II. 4 1953 LO S 8. II (0) 6. 24. .86 Density of Population per sq. mile
1946 265 682 8. 1953 324 8. () 08 Cultivated Extent
1946 million 3.2 2.6 (). 60 1953 ) acres 3.64. 2.97. (). 67 Forests (million acres) 2.76 0.62 2.14.
Source: Census of Agriculture 1952, Part IV — Agriculture
water, the pace of agricultural development in this area is rather slow. Lack of a sufficient number of perennial rivers and the failure to find subterranean water supplies have restricted the development of irrigation almost entirely to the restoration of ancient irrigation schemes. But even with the maximum development of all the irrigation schemes it is estimated that about 2.5 million acres will still remain unirrigable.
Table 2 would give an idea of the land utilisation pattern in the country. Paddy is the most important crop in peasant farming and accounts for a total of about 1.2 million acres of as weddumised land. With the exception of the main plantation crops-tea, rubber, and coconutthe area devoted to other crops is quite negligible. Since there is no scientific basis for the collection of agricultural data with regard to crops other than paddy in this section, (commonly designated "non-export”), we will restrict our. selves to paddy alone in this discussion,

TABLE 2.
Land Utilisation Pattern in Ceylon – 1962.
million acres
Geographical area 6.228
Total State Forests 3.480
Roads, streams, tanks, buildings etc. 1.250 (α Rocky and steep lands and land over 500 ft. etc. 4.750(a)
Available for future cultivation 2.98
Net Cultivated area 3. 83 ()
Paddy I. O5
Tea (). 59.
Rubber 0.674. Coconut 1.070 (α) Other Highland crops including Chena 0.300 (e)
(a) Report of the Committee on the Utilisation of Crown Lands, p. 16,
1953.
Normally, it should be useful to examine the productivity of each of the three factors of production-Land, Labour and Capital. Because of the lack of data again it would not be possible to go into a detailed analysis of the productivity of labour and capital. What can be stated with regard to labour is that there are said to be about a million cultivators working on a total as weddumised area of l.2 million acres of paddy, which in other words means that roughly I cultivator family is handling an as weddumised area of l.2 acres. The total cropped area under paddy for both the seasons — Maha and Yala — in the Island today is l. 56 million acres, which gives an average of 1.56 acres as the cropped area under paddy per cultivator family.
The total number of families in the Island being of the order of 2 millions, each cultivator family has to support an additional family. With the present rate of increase of population at 2.7 per cent and a little possibility of the additions to the cropped area keeping pace with this galloping rate of population, pressure on land is increasing every day.
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TABLE 3.
Cultivated area per head of population 1830-1962
Total Acreage Cultivated
Year Population under Area per
Cultivation head of
Population
(millions) (000 acres) (acres) 1830 ().96 47 (). 43 1840 40 588 (). 42 1850 I.59 722 (). 45 I860 .88 928 0.43 97. 2.4 402 0.58 88. 2.76 506 O. 904 89. 3. () 025 0.67 90. 3.57 248 0.63 I 9 III 4. III 730 0.66 92. 4.50 829 0.63 93. 5.3 33 0.62 1946 6.66 2. () 0.48 1950 7.65 44() (). 46 1962 (). 34. 3. 830 0.37
Note: (a) Figures from 1830–1901 inclusive are taken from the “Statistical Review of the Progress of Ceylon 1823-1902” published in the “Ceylon Blue Book” for 1902.
(b) Figures relating to 19ll-l946 inclusive are taken from the
Census of each year.
(c) 1950 figures which are tentative have been supplied by the
Department of Census and Statistics.
Taking the Overall picture for the whole of agricultural land in the Island, the position is still worse. Between 1946 and 1962, while population increased by 56 percent. the total extent of agricultural land increased only by a little more than 9 percent. This has resulted in increasing the pressure on land. While an acre of agricultural land supported 1.56 persons in 1946, this ratio went up to 2.24 in 1962. In so far as paddy is concerned, the total area under the crop-l. 56 million acres—has to support today a population of nearly 10.6 millions for their staple food. It would be clear that at present just 0.14 acres of paddy
77

land is available per head of population. Obviously, with the present yields of the order of 38 bushells per acre and the per capita consuzimption of a mirimum of 8 bus hels, we need at least 0.25 acres per head at the present levels of productivity, if self-sufficiency is the objective. The balance of food has naturally to be imported to meet the minimum requirements of the population. As would be seen from table 3, even the total cultivated land per head of population has been decreasing slowly over the last 4-5 decades. The only solution to the paddy problem of Ceylon, will thus lie in a further intensification of the peasant agriculture.
Ceylon is one of those countries where people engaged in agriculture directly or indirectly constitute more than 75 per cent of the total population, and capital for the development of agriculture as well as any other industry is rather scarce.
Even otherwise, very reliable information with regard to the investment of capital in paddy is not immediately available. In the absence of all that, it would be rather difficult to work out the capital-output ratio in agriculture, a phenomenon which is quite easy with regard to the industrial sector. In an under-developed economy like that of Ceylon, capital-output ratios are also not of much signific cance, particularly when due consideration is given to the fixed capital stock by way of investment in irrigation and land development. Public sector investment in the develop. ment of agriculture during the last 5–6 years as given in table 4 would show that investment outside land development and irrigation for paddy is rather insignificant.
In the context of what has been discussed above, what is really significant is the productivity of land. Besides increasing the area under paddy, acre yields are extremely important in so far as the problem of this Island is concerned. Before we go over to the actual question of land productivity, it would be useful to examine how far the institutional and other factors are conducive to higher levels of production.
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INSTITUTIONAL FACTORS
Productivity in agriculture is closely linked with the institutional system prevailing in the agricultural economy of a country. This relates to,
l. Land Policy 2. Credit Schemes 3, Price Policy and allied problems.
Land Policy-Ceylon is no exception to the prevalence of the general phenomenon of peasant agriculture being subject to the exploitation of Land-lords. According to the 1953 census, a little less than half the area under paddy was cultivated by peasants who did not own the lands they cultivated. The results of the 1963 survey are not yet available but the position might have deteriorated further because of the continued pressure on lands. Such paddy cultivators have often to pay exhorbitant rents and have no security of tenure.
The Paddy Lands Act of 1959 attempted to solve these problems by granting security of tenure and fixation of rents. It also made it obligatory on all tenant cultivators to cultivate their lands efficiently. Cultivation Committees with representations from tenants and Land-lords, etc. were instituted as bodies incorporated in law for the implementation of the provisions of the Act. They were in addition intended to serve as an institutional device to impart the advantages of large scale cultivation and planning to the small fragmented individual holdings.
Largely due to the legal difficulties, implementation of the Act become rather difficult. As many as 25 thousand tenants have been evicted from the paddy' lands. The legal procedure to be followed before tenancies could be restored were so dilatory that not more than 4,000 out of them could be given protection.
It is true that the implementation of the Paddy Lands Act has been weak, but recent amendments to this Act are trying to remove the existing lacuna in the legislation. It can be reasonably expected that the existing set up of the Cultivation Committees and the education of the cultivator
'79

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Page 55
in due course will go a long way in improving the lot of the cultivator so as to give him sufficient security from exploitation by the land lords.
Credit Policy-In order to overcome fundamental defects in the institutional structure a new Credit Scheme has been introduced from the current year 1963/64. Some of the salient points under this scheme are
1. the share value to be paid by the member of the Co-op. Society asking for credit advances can be paid in instalments at harvest time. The entire value of the share amounting to Rs. 50/- can be paid during ten harvests at Rs. 5/- per harvest:
2. all the over-due loans are to be reviewed and where the fault is proved to be due to factors beyond the control of the society steps would be taken to write off such loans. Where the fault has r been due to some other cause such as fraud or mis-management a definite, course of action would be initiated to dispose of such overdues and to render such societies credit-worthy.
3. no cultivator who is a member of the Co-op. Society should be entitled to the benefits of the GPS applicable for paddy;
4. The total amount of credit admissible to a cultivator is enough for him to resort to all the improved methods of cultivation. The scheme provides for a farmer who owns one share in his Co-op. Society credit at the rate of Rs. 175/- per acre cultivated by him up to a maximum of Rs. 500/- for the first season, while a member who owns two shares may go up to a maximum of Rs. 1000/- also for the first season at the same rate of Rs. 175/- per acre cultivated. If a particular piece of land is cultivated twice, the maximum credit limits are further raised to Rs. 750/- and Rs. 1500/- respectively.
Apart from ensuring the farmers of adequate credit for production purposes, the new scheme also provides a
81
a

marketing advance to farmers about one month before the harvest is due in order to insulate them from the operations of traders and middlemen who are particularly active at this time. The limit for such advances payable to a single cultivator is fixed at Rs. 200/- or 20% of the yalue of the crop which the farmer expects to sell to the GPS from his current harvest, or 20% of the value of the paddy from his current paddy which he actually sold to the GPS during the previous corresponding harvest, whiche ver is less.
GUARANTEED PRICE SCHEME
Ceylon is one of those countries where quite an efficient CPS for paddy has been in operation for more than a decade. Every cultivator is eligible to sell off his produce to the Government through the Co-op. organisation at Rs. 12/- per bushel (about 30 lbs. of rice). Along with this GPS, each citizen of the country, including the cultivator, is also entitled to two measures of rice per head per week at -/25 cts, a measure (2 lbs) for his consumption. This in other words means that while the producer is paid roughly at the rate of Re. 1/- per measure for the rice produced by him at his farm (and his cost of production is nearly half that) he has his consumption requirements
su popolied, at —/25 cts, a measure.
pp
Other incentive Schemes
Along with these institutional factors, there also exists Fertiliser Subsidy and Crop Insurance Schemes which normally go a long way in helping the cultivator to resort to into nsive methods of cultivation. With due consideration to the economic backwardness of the cultivator, the Government of Ceylon has been subsidising the use of fertilizer for paddy for more than a decade. Upto 1962, the subsidy scheme made a distinction between members of Co-operative Societies, cultivators applying for fertiliser through the Cultivation Committees, and those making direct purchases from the Department. Members of Co-operative Societies as well as cultivators obtaining their requirements through Cultivation Committees were allowed a subsidy of 50% for cash sales and 33% when on credit. Cultivators making direct purchases from the Department for cash were entitled to a subsidy of 33 per cent only, The matter was re-examined in
82 II.

Page 56
1962/63 and the present position for the grant of fertilizer subsidy is as follows :-
(a) A subsidy of 50 per cent to all paddy cultivators whether members of Co-operative Societies or not who wish to obtain fertilizer on payment of the balance 50 per cent of the cost of the fertilizer in cash;
(b) The continuation of the 33 per cent subsidy to members of Co-operative Societies who wish to obtain their fertilizer on credit to these Societies.
Under the Crop Insurance Scheme, the area under insurance has been extended for the first time since the inception of the scheme to cover a total paddy acreage of 0.2 million acres in 16 districts. This means that roughly l6 percent of the total ass weddumised paddy land in Ceylon has now been brought under Crop Insurance. Target for 1965 is 300,000 acres. Commencing from the year 1963/64. damage by wild elephants has also been included as an additional cause of loss against which insurance protection is offered. The Act now provides for losses on account of – Lack of water, Drought. Excessive Water, Floods, Insects. Wild Boar, Wild Elephants, Adherence to methods of farming approved by the CAS, Plant diseases.
The maximum coverage offered per acre varies from Rs. 100/- to Rs. 180/-. These coverages are offered to insurers provided they follow the minimum practices specified in the Act. محصبر
PRODUCTIVITY OF LAND
Ceylon has at present an average yield of about 38 bushels of paddy per acre equivalent to roughly 1,040 lbs. per acre. Crop cutting experiments in Ceylon were started in 1952, and yield data before that period are not very reliable. Compared with 1952 as base, there has been an increase of 23% in the acre yields from 30.9 bushells
in 1952.
When compared with some of the selected countries in the world and analysed over a longer period of about 50 years, the average yield of rice in Ceylon has gone up by 1.29% and is quite comparable to some other countries
83

in the region. Whereas: Ceylon occupied the second position with regard to rice yields during the years 1909 - 1913, it has now come quite high up from among most of the rice producing countries in the World.
Grist distributed the various rice producing countries in the world according to different degrees of latitude North and South of the equator, and from among South East Asia, grouped Ceylon with Malaya and Indonesia. Ceylon is already well on its way to catch up with the present
yields in Malaya.
Whether or not this is due to higher prices offered to the cultivator is difficult to say, more so because the scheme of guaranteed prices at the prevailing rates was introduced about 10 years back. Table No. 5 however, throws an interesting sidelight on this aspect of the problem.
| A | 3 || || 5.
Price, Yield and Income per hectare of paddy
in selected Asian Countries.
tOn `ಕ್ಷ್ Gross in come Οountry 1957 59-957 «بر) hectare
Rupees 1 ܓ݂ܠ}()( kg. upees
Japan / 704 46 3237 China (Taiwan) 286 3 () 857 Korea Republic 38. 29 ()95. Ceylon 2/ 576 7 () () () Malaya 2/386 2. 809 Philippines 557 2 666 Pakistan 3/3()() 4. 428 Thailand 29 4. } () India 24 276 Viet-Nam Republic 90 3 248 Burma 2/43 6 228
1 / Paddy equivalent of form price for husked rice. 2 / Minimum guaranteed price. 3/ Government procurement price, 1957/58.
Source: The World Rice Economy, Volume II-Trends & Forces (30.
Commodity Bulletin Series. No. 36, p. 24, F.A.O.)
| 84

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While Ceylon pays more or less the highest price (with the exception of Japan) per ton of rice, average yields here are still low as compared to Malaya, Philippines, Korea and China (Taiwan). One may, all the same observe from a study of the above table that while it may be good to provide incentive prices to the cultivator, it is not necessary that productivity of land will have a direct relation with !اسلام such prices. Land productivity is normally co-related to the application of the improved methods of cultivation and the availability of various input factors to the cultivator at reasonable prices as well as at the time required.
Even a statement of this nature may be difficult to substantiate in a country like Ceylon where agricultural data are not very reliable. While irrigated areas under paddy increased by 62% during the period under discussion and fertiliser consumption by more than 800 percent, productivity of paddy has hardly gone up by about 23 percent. Table No. 6 supplies the necessary data in this respect both with regard to the actual quantities consumed as well as an index with base as 1952. Consumption of fertilisers for paddy alone during the last 3–4 years has been going بر up by about 9,000 tons every year. With a steady increase in fertiliser consumption, acre yields have however, shown some sort of stickiness. During the year 1960, Ceylon had an average yield of 36.3 bushels per acre, and it has gone up to only 37.9 bushels per acre in 1963.
A study of the last 10 years for the whole of the Island would indicate that while there is an increase of 39 percent in the harvested area, paddy production has increased by 70 percent. But in spite of this increase in the production of paddy during the period 1952–63, per capita production has increased only by 28 percent, which in other words means that the existing increases of production are enough just to meet the natural increase of population alone. This has resulted in an actual increase in the import of rice during the period under discussion from 0.439 thousand tons in 1952 to 0.515 thousand tons in 1962, although collections under the guaranteed price have also increased 18 times during this period.
The analysis can be further taken down to the district level. All the 22 districts in the Island have been
85
 
 
 
 
 
 
 
 

****** ~ ~ ~~~~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ | ¡ ¿ CEYLON81.1 49.61473.758 36.537.2 36.9 Batticaloa 6.22/ 46.92/ 82.9572/ 35.038. 1 36.6 Vavuniya32.833. 250. 1664/ 35. () 4/ 37.436.2 Kurunegala 9/86.591.]118.37732. 434.4 33. 4 Colombo 9/85.59.676. 7]334.731.2 33. () Matara 8/ 71.025.781.33233. 430. 4 31.9 Puttalam/Chilaw78.522. 727.78231. ()31.3 31.2 Jaffna82. 729. 474 , 4 !4028.034.]. 3].] Ratnapura 8/79.334.553.964 29. O 30.8 29.9 Kalutara 8/ 79.97.573. 71027.6 28.7 28.2 Galle 8/77.48.079.0104/ 25.9 4/ 27.8 26.9
1/ Average for the last one year.
2/%%ɔɔ ɔɔ„ two years.
3/99„ „ „ three „
4/%%oo oo„ four „
5/ɔɔ„ „ „ five „ unless otherwise stated.| |- 6/ Included under Badulla District.
7/99„ Batticaloa99
8/ Districts classified under Wet Zone. 8/* Certain areas of these districts are dry. 9/ Certain areas of these districts are wet.
Source: AG/P/12.

Page 58
TABLE
AREA, PRODUCTION, GPS COLLECTION AND
1952 -- 1
Asweddumised* Harvested area Area irrigated for GPS c ಕ್ಷೌy paddy sowing paddy ра
Actual Actual Actual Actual '000 acres Index 000 acres Index 000 oes Index
Klasse
1952 964, 00 936 00 588 I00 1.535
1953 964 00 809 86 488 83 0.32
1954. 982 102 1022 109 655 III 3.65 1955 0.32 07 1092 II 7 72. 23 3,255
1956 - - 97 98 60 04. 9.66
1957 - 968 103 626 106 3. III
1958 - - 1054 II.3 762 30 I6. 26. 1959 O7 II 5 104.4 III 700 II 9 16. 642
I960 4. 18 III 84 26 834. 42 2.836
96. 160 120 II96 28 862 47 21,967 1962 195 124 269 136 902 I53 28,657 1963 230 128 1297 139 950 I62 27, 760
*Area which is prepared for the cultivation of paddy, but the as weddumised and harvested
 

6.
FERTILISER CONSUMPTION IN CEYLON,
963.
ollections Fertiliser Production Per capita iddyn consumption paddy Production paddy
Index Index ဂျိုးမျိုး Index 蠢E. Index
O() 2,554 00 28.9 IOO 3.58 00
2. 3,912 53 2.9 76 2.64. 74. 236 6,945 272 3. 108 3.65 O2 864. 8,989 352 35.7 24 4.09 II.4.
629 12,837 503 27.5 95 3。08 86 854. 14,139 554, 3.3 08 3.42 96 1059 16.942 663 36.6 27 3.90 09 1084, 26.844 105. 36.4 126 3.78 106 1423 20.340 796 43.0 I49 4.35 122
43. 29,299 47 43。2 49 4.25 II9 1867 38,750 57 48. 166 4.6 29 1808 47,930 I877 49.2 70 4.59 28
is not actually sown.
less than the sown one.
Sown area is always less
than

Page 59
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Page 60
TABLE 7.
RELATION OF AVERAGE PADDY YIELDS TO SIZE OF HOLDING AND IRRIGATION IN EACH DISTRICT OF CEYLON.
YIELD PER ACRE
Percent paddyExtent 5/Gross acreage駐----(BUSHELS) DistricthelaeosaᏣᎱᏋS*sown 5/as % of size group000 acres1000 acresGross acreage
S@WynMaha 5/Yala 5/Average Moneragala6/4/ II. 94/ 14.5821/ 55.3 1/ 49.552. 4 Polonnaruwa18. 773.376.29656.448. 152.3 Nuwara–Eliya 8/93.224.324. 7984/ 51.9 4/ 47. I49.5 Badulla 8/*91.530. 636. 2853/ 49. I 3/ 49.549.3 Kandy 8/93.043.675.55851.744. 248.0 Kegalla 8/94.910.947.22347.]43.945.5 Matale 8/*94.423. I33.86843.341. 442. 4 Hambantota21.961.867. ()9241.343.]42.2 Trincomalee25. 543.054.47938.344.941. 6 - Anuradhapura88.2109.5110.89941.641.241. 4 Mannar49.928. 731. 49]40 . ]38.539.3
A manarai7/2/ 91 - 12/ I 19. 9Ĵ 762/ 36 - 3. 2/ 38 337 3

arranged in the order of acre yields of paddy in Table 7. The percent of paddy area per I's acre size group and irrigated area for each district are also shown. The districts marked 8/ fall in the wet zone which has an average of more than 75 inches annual rain fall.
The highest yields are to be found in the Moneragala and Polonnaruwa districts. These two districts which represent the recent colonised areas have the ideal conditions for growing paddy. The soils are rich and the size of holdings is much above the average in the Island and controlled irrigation is available for practically the whole of the paddy area.
it would be interesting to note that the second best group of Nuwara Eliya and Badulla districts have practically the whole of the paddy area below I's acre size groups but that irrigation facilities are available to a large extent. These districts are in a position to maintain the high level of productivity. The same pattern is not, however, being maintained by Puttalam-Chilaw where 80% of the paddy area is irrigated and nearly 78% of the area falls below I's acre size group. Yields in this district fall much below the average in the country. The only explanation for such a phenomenon can be found in the fact that the average cultivator in this district is not prone to improved methods of cultivation and that the extension services of the Department of Agriculture have got to be strengthened so as to educate the cultivator to attain higher levels of productivity which should otherwise be possible. Same would be the fate of a district like Anuradhapura or even Hambantota
where ideal conditions exist by way of full irrigation facilities for the whole of the paddy area.
As has been emphasised in the pages above it might not be possible to make any categorical statement about
the Importance of one or the other factors leading to higher levels of production. Irrigation, fertilisers (including organic
manures) and improved seed can definitely be isolated as ܐ. to give first priority to the development of paddy but under conditions of Ceylon agriculture weedicides would also seem to be very important because it has been observed that in certain parts of the country a major
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portion of the plant food is consumed by the weeds Unless some economic method of controlling weeds are evolved and spread among the cultivators, it would be rather difficult to raise the levels of productivity in the Island. With the various incentive schemes already in operation, facilities provided by nature, and an improved extension service, Ceylon should be well on its way to achieve much higher levels of productivity.
87
*T

DRY ZONE CLIMATOLOGY
GEORGE THAMBYAHPILLAY
“........ the missionaries of the Indic Civilization in Ceylon, once achieved the TOUR DE FORCE of compelling the monsoon-smitten highlands....... to give water and life and wealth to the plains, which Natnre had condemned to lie parched and desolate........ அத
Toynbee in A Study of History (1934),
vol. II, p. 4.
IN seeking to provide adequate evidence and substantive Weightage to his them. - “challenge and response' - in the context of history, Toynbee in his voluminous Study of History, has drawn upon the evidence left behind by the ancient kingdoms of south and southeast Asia, including that of the Dry Zone kingdoms of Ceylon. To Toynbee, the varied and intricate irrigation network, as is to be witnessed even to this day in the myriad tank-landscape of our Dry Zone, is clear evidence of man's positive “response” to the “challenge” posed by the “plains, which Nature had condemned to lie parched and desolate'. It was indeed human ingenuity that eventually rendered this vast and desolately "arid landscape, into the “rice-bowl that it was centuries ago. The we was and kulams, the anicuts and elas, continue to bear mute witness to the engineering ingenuity of our ancients. They were, thus able to make possible the flowering of the “golden age” that was Lanka's between the fourth and the twelfth centuries. The excess water incident upon the monsoonal rainfall, instead of being allowed to run to waste into the Indian Ocean, was stored in the ancient reservoirs and then directed by miles of elas, to water the desolate plain, to render it, as has been claimed, the granary of the East.
That our ancient civilization flourished in this naturally arid landscape, was indeed due to irrigation. This was
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true also of our neighbouring Carnatic, which forms a climatic homologue to our own Dry Zone. Both areas were subject to seasonally recurrent droughts - the Dry Zone of Ceylon and the Tamil Nad. In reviewing the attempts at recent “peasant colonization” in south Asia, Farmer underlines throughout his research findings, the role of irrigation in sustaining these ancient civilizations. Thus, “the Dry Zone of Ceylon is climatically very much like the corresponding part of India across the water ... the Tamil Nad. ; in fact, the ancient Sinhalese civilization, like the civilization of Madras, existed only because of irrigation (l).
It is clear, then, that the recurring seasonal drought, has been a persistent theme in the climatic regime of the Dry Zone. It is, however, noteworthy that the prolonged droughts observed in recent years, has even evoked the suggestion that our climate has perhaps changed for the worse in recent decades. This, seemingly mistaken suggestion, is nevertheless, not entirely without foundation. Since the 1940s, drought conditions have seemed to be more persistent than in previous decades. Recent researches into this aspect of our climate (ll, l5), have revealed that the island has, within the last eighty years, very definitely exihibited “dry phases" and “wet phases"; the island at present is characterised by a “dry climatic phase'. However this climatic-phases are not confined to the island but in fact constitute part of a larger pulsation involving the tropical zone and even the mid-latitudinal Zone (20).
Apart from the mute evidence available in the Dry Zone, in its intricate irrigation network, in support of a longcontinued recurring seasonal drought, there is also available authentic documentary evidence in this context. In our ancient chronicle — the Mahavamsa — references point to prolonged droughts causing famine and misery; there is also the reference to even secular drought phases in a later work written by an Englishman, towards the end of the 17th century (3).
While, the attribute of drought has come to be accepted when reference is made to the Dry Zone, it is indeed paradoxical that during certain months, the rainfall in this area
89

far exceeds that in any other area in Ceylon. Often, it is also, that in some years, such rainfall in the Dry Zone exceeds more than two hundred percent of the mean annual rainfall (6). The heavy diurnal rainfalls of over twenty inches, experienced in Ceylon, have been confined to the Dry Zone in particular; such rainfalls are incident upon the seasonal cyclonic storms (16). It is indeed, also noteworthy, that from an over-all rainfall standpoint, no part of this island has been deemed to be "arid, to be brought under investigation, in the UNESCO sponsored international programme on Arid Zone Climatology; no rainfall station in Ceylon records a mean annual fall of less than thirtyfive inches. Indeed, from a climatological standpoint, the designation, DRY ZONE, seems a mis nomer.
Despite these considerations, the characteristic of seasonal aridity, is accepted as integral to the climatic regimen of the Dry Zone. It is in this context, that during the British regime, a programme of restoration of the ancient irrigation works, was inaugurated and which continued systematically right up to the 1930s. To empha. size the significance of the need to “regenerate and retransform the Dry Zone into the granary that it was once, in 1932 was inaugurated the modern phase of peasant colonization, involving a planned programme. At the present time, with a background of three decades of evolution and growth, the total peasant colonies number fifty-seven in the Dry Zone. The total acreage brought under this scheme is little less than 200,000 acres (195, 570 acres in 1959), with the Gal Oya “colony comprising a 26,000 acre allocation. In the recent past, succeeding Governments, have placed priority emphasis on the development of the Dry Zone, for it is in this region that is envisaged the growing of sufficient food-crops to support a rapidly growing population. Many new cultivation techniques, the Japanese transplanting technique in respect of paddy, use of tractors, use of improved ploughs, use of pure-line seed paddy, spraying of weedcides, use of artificial manure, adoption of crop rotation, -have been tried out but the overall increase in food-crops has not been commensurate with the total amount of outlay that has been expended on these schemes. -
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From the climatic standpoint the Dry Zone has been treated as a single unit, with its weather regimen overgeneralized. The Maha Illupalama Research station located in the Dry Zone to understake meteorological observations and investigations into other climatic aspects such as evaporation, transpiration, water need and the like, has had but a few years of existence. A thorough understanding of the significant characteristics of the Dry Zone climatology, must obviously constitute a sine qua non, for the optimum exploitation of this agriculturally vital region. Some of the neglected aspects of climatology pertain to wind regimes, potential evapo-transpiration investigations to estimate water need, micro-climatic studies of judiciously selected localities, bearing in mind such considerations such as 'exposure’, localized wind-effects (fohn wind-effect, evaporation-inducement etc), the reliability of rainfall incidence, any secular over-all fluctuation patterns and the like. The attempt will therefore be made in this paper, to focus attention upon some of these aspects, while presenting the weather and climatic regimen of this vital region.
THE DRY ZONE DEFINED
In spite of the numerous and continued references to the Dry Zone of Ceylon in literature, pertaining to agricultural and irrigation considerations and in general to the geographical context of the island, yet a truly definitive demarcation of the Dry Zone has so far not been satisfactorily attempted. It must be conceded, however, that from a qualitative standpoint, there is indisputed acceptance that it is the prolonged drought season from June to September, that is characteristic of the Dry Zone. This is of real significance, because paradoxically enough, it is during these months that the Southwest Monsoon is in full dominance over the island and is responsible for the heavy rainfall in the southwest quadrant of Ceylon. In effect, it is this very same moisture-laden Monsoon that eventually dominates the Dry Zone but as a moisture-bereft and drying wind. After being induced to precipitate all its precious moisture on the windward flanks of the central Highlands, it crosses the north-south trending mountain backbone of the island (Fig. 1) as a dry wind and imposes its quality of aridity to the entire Dry Zone. The rainless season
91.
 

Dry zone of CE. YLON
os 75 "annual sohyer
an 2 O'SW monsoonal
(Sohyer
éj over う○○○ fee/ 3 /OOO-5OOO feet
GT fins
Fig. 1.-The DRY ZONE of Ceylon defined by 20-inch SW Monsoonal isohyet, with the 75-inch annual isohyet superimposed. The major irrigation works (abandoned and in use) have also been indicated.
The DRY ZONE HIGH LAND is also identified, viz., the area over 1000 feet east of the SW monsoonal isohyet.
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MEAN ANNUAL Rx RAINFALL DA?Y ZOAVA
(1881-1950) of CEYLOW
D < 50
Se asonal Rainfal
( 1881-1950)
MAR r
ΔPR ίί.
f is
Fig.
2.-Mears annual Rainfall and Seasonal Rainfall in the DRY ZONE of Ceylon. All values
have been computed from the long period data, viz., 1881-1950. The recognized seasons (after Thambyahpillay, 1954) are :-(a) VERNAL CONVERGENCE-CONVECTIONAL-March to April, (b) PRE-SW MONSOONAL-May, (c) SW MONSOONALJune to September, (d) AUTUMINAL CONVERGENCE-CONVECTIONAL-CYCLONIC-October to November, and (e) NE MONSOONAL-December to February.
 
 
 
 
 

then inhibited any agricultural activities and consequently irrigation-water became essential to maintain any form of agricultural pursuits. The maze of irrigation works then had the double duty of storing water from the moistureladen monsoons and then in releasing through elas and distributary channels this stored water for use during the dry season.
The first attempt to demarcate with some definiteness the Dry Zone was the use of critical isohyets; the 75-inch mean annual isohyet was accepted as a working-boundary. This boundary coincided with the Deduru Oya in the north, the Wallawe Ganga in the south and with the 1000-foot contour in the east (Fig. 1). This meant that nearly threequarters of the island constituted the Dry Zone and included the Jaffna Peninsula. Further within this vast region, was also recognized and defined by the 50-inch mean annual isohyets two sub-regions, designated the Arid Zones in the northwest and in the southeast (Fig. 1). The rest of the island, namely the remaining quadrant in the southwest was designated the Wet Zone. It is clear that these zones were in effect defined only from the rainfall criterion and not truly from a climatic standpoint.
The real inadequacy of this 75-inch annual isohyet as the Dry Zone boundary, was in respect of the exclusion of a large part of the area east of the central Highlands; this included almost the entire Uva Basin (or the Welimada Basin) which is strongly characterised by a climatic regimen so closely parallel to that of the Dry Zone. The Southwest Monsoon period (June to September) was one of marked drought and the total rainfall during this season less than 20 inches (Fig. 2). The many irrigation elas and some vewas in this Basin, was substantive proof that a long drought season necessitated the use of irrigation water for agriculture during the prevalence of the Southwest Monsoon. Furthermore, the vegetation in this Basin also is closely similar to the typical Dry Zone deciduous forest and jungle eco-system, with modifications imposed by the altitudinal factor. The sub-montane grassland-the patana-here is seen to reflect the effect of aridity and hence a drier facies, designated the Dry Pataтas (6).
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In the light of these many considerations - clima tological, vegetational, irrigational - it is clear that the Dry Zone needs to be redefined. It has beer brought earlier that the 75–inch annual isohyet constitutes an un satisfactory Dry Zone boundary. The Uva Basin should with justification be included within the Dry Zone, for reasons already adduced. The author's attempt to apply the Koppen climatic classification, with justifiable modifications (18) has demonstrated that the regions with effective rainfall attribute - namely f = should be excluded from the Dry Zone (Fig. 4). This boundary then so demarcated coincides also with the 20-inch Southwest monsoonal isohyet. The latter will then permit the Uva Basin to be included within the Dry Zone. It is seen that this 20-inch SW monsoonal isohyet coincides with the 75-inch annual isohyet in the north (Deduru Oya boundary — Fig. I), and in the south departs slightly from the 75-inch isohyet. In the east, it is noteworthy that the 20-inch isohyet runs closely to the central mountain backbone and quite rightly excludes the Knuckles and the Rakwana massif from the Dry Zone. This eastern boundary forms a true climatic divide, because the ‘wet’ and “dry” facies of the patana grassland occur on either side of this 20-inch isohyet. It is natural that such a single isohyet cannot be accepted as a truly adequate boundary. All climatic boundaries (with exceptions) are transitional and so is it in this context as well. It will be seen from the Koppen map (Fig. 4) that the Amwi climatic regions lie adjacent to the northern and southern portions of the 20-inch isohyet and in the east it is the Csbi climatic region that is the transitional zone. It is this transitional zone that has been recently designated the intermediate zone by the Canadian Hunting Air Survey
Corporation (1963, 1964).
In view of the Uva Basin being inteluded within the Dry Zone, as defined by the 20 - inch SW Monsoonal isohyet, and it being an elevated region (1500–4000 feet), it is appropriate that the Dry Zone ble said to constitute an (a) Upland Dry Zone and (b) a Lowland Dry Zone.
WEATHER REGIME OF THE DRY ZONE
It is usual in climatological practice, to adopt a month to month description of weather regimes, beginning
95
//

with the Calendar Year in January. However, detailed researches into the climatology of the island, as carried out by the author, has clearly demonstrated that the weather regime, may be recognized to constitute of well defined seasons, and that the “climatic year begins in March (6.9, II) and not in January. This month (March) also thus, initiates the seasonal weather rhythm and so it is that the “seasonal year ranges from March to February. The author's own demarcation of the island's weather regime into its seasons, has now been adopted and used recently for investigations into river-flow studies in connection with the River Basin Projects Programme (2) in Ceylon. In the present analysis, the same season-based descriptions will be adopted.
(a) The (Vernal) Convectional-Convergence Season (March to April).
In March atmospheric conditions over the island are being established that reflect simplified climatic controls both planetary and geographical. This is the period when the planetary control exercised by the island's latitudinal position becomes most exemplified. The Inter-Tropical Convergence Zone (ITCZ) interposed between the hemispheric Trades, moves into the equatorial latitudes and is centred about the “thermal equator - viz., 5° N latitude. The island being located between 5° N and 10° N, is naturally confined to within the ITCZ and as such its influence is clearly exerted. Doldrum conditions are experienced and this permits for the establishment of the local geographical control, namely, convectional circulation consequent upon high temperatures, high humidity and insularity. It is only when the ITCZ. boundary - the Northern Convergence Zone (NCZ) - crosses the island, that there is experienced the sudden deterioration of weather. Apart from this circumstance, it is convectional Weather par excellence that constitutes the weather theme of this season, over the entire island.
In the Dry Zone, the significant effect of the constant and alternating interplay of off-shore and on-shore circulations - the land breeze and the sea breeze — are varied, in view of the coastal and inland aspects of the
different stations. However, the clear morning skies-cloud spattered early afternoon skies — the cumulus build - up
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:Հ ) : : : ,
30. (1881- 1950)
A/g°AAV AAM/W0/4 t. Agaw a WAV/4
De // A'r 10 Aw5 AREFUL 4 7^/VE YR ( (Ո S. vaa/ae/L/ τΥ (%)
፭›E AየC £ /V r
திட 8
β - γ2
፱2-46 Oجمے--6/ [IIIII| ごc. : ہے O -3 26ےα . ليز
Awsta ay aAwawa. Mga W AWAwUa L goሠy : $ r4ለ04/የp waA/ae/t/ 7 y
DAFW/477 OAVS N. COE affo/EN r(%)
Fig. 3. Rainfall Variability in the Dry Zone. All values based on the
long - period data - 1881 to 1950.
97
 

by late afternoons — the deluge from the resulting thunderstorm – the clear cloudless night skies -- constitute the daily regime practically everywhere over the island. Any variation from this theme, is a reflection of localized aspect', “exposure” and such condition. The afternoon thunderstorm then becomes an epitome of the weather theme during this period.
Temperatures are high, everywhere in the Dry Zone, during March and April. The mean monthly values range over 80°F, except in the Upland Stations, where the altitudinal influence is reflected, as between Badulla (2225 feet) with 73.2° F and 75.2° F and Diyatalawa (4104 feet) with 67.6° F and 69.1 °F, during the two respective months (Table A. 2). The higher temperatures in April, are as to be expected, in view of the overhead Sun. Diurnal temperatures are also high during these months. This effect may be explained by the clear mornings permitting strong incidence of incoming solar radiation as contrasted with the clear cloudless night-skies which then permit rapid loss of nocturnal radiation (Table A. 3). However, it is significant that a number of Dry Zone stations (viz., Anuradihapura, Badulla, Diyatalawa, Jaffna, Mannar, Puttalam and Hambantota) exhibit lower diurnal temperature ranges in April than in March, though in fact, temperatures in April are higher than in March (Table l). This may be easily explained. By April convectional conditions are fully established and hence the higher humidity incident upon the increasing rainfall and the greater cloud cover; these in cumulative effect, bring about the negative diurnal temperature range anomalies. Only Batticaloa and Trincomalee show higher diurnal ranges in April than in March.
These are also the months of marked convectional activity and this will be reflected in the incidence of thunderstorms (Table A 5) Again, as is to be expected, the incidence is higher in April than in March. The heavier rainfalls in April is seen to commensurate with the greater number of thunderstorm days and the increasing number of “rainy-days'. The comparative picture of the correlation between thunderstorm incidence, “rainy days and amount of rainfall is demonstrated for a number of Dry Zone stations, with varied locational situations (Table 1). It is
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TABLE I. Comparative analyses of mean monthlytemperatures (°F), mean monthly diurnal tempe
rature ranges (°F), mean monthly rainfall (inches), rainy-days and thunderstorm incidence in March and April at Dry Zone stations.
Station and LocationMarchApril ab|-Cde|a.bCd€.
( i ) Lowland Coastal (Eastern)
Batticaloa80.210.373.5382.211.1- 62.38
Trincomalee80.99. ()62.3283.311. 462. 17 (ii) Lowland Coastal (Northern)
Jaffna82.212.731.5284.79.452. 27 (iii) Lowland Coastal (Western)
Mannar82.214.341.9884. 212.573. 413
Puttalam81.316.863.0682.713.2104.98 (iv) Lowland Coastal (Southern)
Hambantota80. 412.593.41082.011.3103.9.14 (v.) Lowland (Inland)
Anuradhapura 81.219.384.1782.916.8126.414 (vi). Upland (Inland)
Badulla73. 217.9 125.0|-75.217.8167. ()-
Diyatalawa67.619. I134.81069. I17. 4176.618
a=monthly temp. (°F) b-diurnal temp. (°F) c=rainy-days d=monthly rainfall (inches) e=thunderstorm days
Information collated from a number of sources.
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Climatic fregions of
f/beg DAPY ZOAVE
fnodified by
* KOPPEMw ThambyahpỉWay, 7954 7/70/7//7////4/7/:
Fig. 4. The Climatic Regions of the Dry Zone of Ceylon, according to the Koppen and Thornthwaite classifications, on the basis of modifications introduced by Thambyahpillay (1954).
to be seen that the Upland inland stations of Badulla and Diyatalawa, are seemingly more favoured from the standpoint of rainfall incidence and especially of number of “rainy days and days of thunderstorms. The Uva or Welimada Basin (Fig. 1) where these two stations are located is a region of strong convectional activity. This Basin, and the corresponding western counterpart — the Hatton Plateau in the Wet Zone - are suitably located in plateau positions on either side of the Central mountain Ridge and hence are favoured for convectional activity (8). It is when the ITCZ. boundary crosses Ceylon in April, that weather is seen to suddenly deteriorate and disturb the regular convectional sequence.
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The regional rainfall pattern reveals that almost the entire Dry Zone receives less than five inches in March, while in April, a number of stations record between five and seven inches. For the season (March and April) the regional pattern shows a low value for the Jaffna peninsula (less than five inches) while the amount is seen to increase from the north towards the southwestern sector (Fig. 2).
This is a season of highly variable winds, as is to be expected in the context of the strongly developed landbreeze and sea breeze rhythm. No specifically aligned air streams are yet established, though by mid-April a variable southwesterly component wind stream may be observed to intrude into the southern sector of the Dry Zone, especially about the Hambantotal environs. Though this season is definitely not susceptible to depressional activity, yet it is notew worthy that one of Ceylon's disastrous cyclones, struck the Batticaloa - Trincomalee coast in March 1907 (16). The only other occasions during a 120 year observation period, when cyclonic storms struck the Dry Zone during this season, were in April 1937, March 1938 and April 1939. All these storms caused moderately heavy rain along the Batticaloa - Trincomalee coast and in the Jaffna peninsula
(1937).
(b) The Pre-Southwest Monsoonal Season (May)
During the latter half of April, the atmospheric conditions over the island begin to portend the change that is to be finally initiated with the onset of the SW monsoon. The southwesterly streamlines are already evident in the southwest quadrant of Ceylon and the anemometer at Hambantota itself records rather gusty southwesterly streamlines. By May this feature is fairly well established, at least in the western part of Ceylon. In the Dry Zone, occasional stronger gustiness is evidenced and hence is responsible for the observable change in the weather regime.
The convectional circulation of the previous season is not yet eliminated, for some Dry Zone stations continue to exemplify true " convectional weather. The diurnal temperature ranges continue to exhibit positive changes, as for example at Badulla, Batticaloa and Trincomalee (Table A. 3) while temperatures also are on the increaae (Table A. 2).
().

It is noteworthy to observe that it is these stations that lie to the lee of the central mountain chain. In view of their sheltered locations, these stations are bereft of the influence of the southwesterly streamlines and hence convectional weather continues to be the theme. However, the amount of rainfall shows significant decrease (A. 4). The number of thunder days, however, show no correspondingly
appreciable decrease (Table A. 5).
A comparative analysis of mean monthly rainfall. mean monthly temperatures and mean diurnal ranges (Table II), demonstrate rather interesting features during this season in the Dry Zone. The significance of aspect is clearly evident.
TABLE III.
Comparative weather features at selected Dry Zone stations: MAY
(Temperatures in of; rainfall in inches)
Mean monthly Mean diurnal Mean monthly
Station temp. range rainfall
Amount change Amount change Amount change
Anuradhapura 83.2 十0.3 l4。2,一2.6 3.5 - 2.9
Badula 75.8 - 0.5 l8.6 - 0.8 4.7 - 2.3 Batticaloa 84.0 + 1.8 12.3 + 1.2 I. 7 - 0.6 Jaffna 84.8 - 0. I 6.5 - 2.9 2.0 - 0.2 Mannar 85. () + (). 3 8.9 3.. 6 II. 8 — I : 6
Hambantota 8.8 - 0.2 9. - 2.2 4.3 + (). 4
Data collated from a number of sources.
It is to be noted that all stations, with the exception of Hambantota, exhibit an increase in monthly temperature and an overall decrease in monthly rainfall. The variations in the changes in diurnal ranges, are indicative of the aspect or "exposure locations (Fig. 1). Thus, it is, that while the lee-location stations of Batticaloa and Badulla. alone show positive changes (this is true of Trincomalee and Diyatalawa, not shown in the Table), all other Dry Zone station exhibit negative changes.
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Hambantota, in the context of its coastal location and lying athwart the moisture-laden low-level southwesterly streamlines, reflects the immediate change of amelioration in its temperatures, only a slight decrease though from 82.0°F to 81.8 °F. It is however, noteworthy, that of the Dry Zone stations, only Hambantota shows an actual increase in the May rainfall. The actual rainfall received at Hamban tota from year to year, is very variable and in some years very much greater than the mean increase shown in Table II. Thus, when the ITCZ. boundary crosses the island, convergence weather and incident rainfall, can be fairly high. Furthermore, the observed “surges' in the pre-Monsoonal streamlines (19) can also induce heavier precipitation in those years, when these “surges' reach the Hambantota environs.
This season, then, is the very important transitional phase, occurring in-between the strong convectional regime of the March–April Convergence-convectional season and the true Southwest Monsoon season that is to be fully established not until June. The weather regime at different stations in the Dry Zone, vary according to the degree to which either of the controls-convectional or pre-monsoonaldominate while engaged in a pari passu sequence and also on the exposure of the station-locations.
(c) The Southwest Monsoonal season (June - Sep
tember)
The initiation of the Southwest Monsoon season, has vital agricultural significance to the Dry Zone. It is paradoxical that it is during this very season that there is presented in the island, two contrasting rainfall zones - a very wet zone and a very dry zone. It is even more paradoxical that it is the very same SW Monsoon that brings copious rainfall to the smaller southwest quadrant; it is at the same time, primarily responsible for the larger Dry Zone that covers nearly two thirds of the island.
It has already been demonstrated (19) that the true Southwest Monsoon does not dominate our island's environs until the last week in May and the first week in June. And then for nearly four months the agro-climatological characteristics of the island is dominated by this Monsoon. It is not realized that it is the geographical circumstance
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of a north-south trending central mountain chain that has rendered the Dry Zone, a region of virtual seasonal drought, during the SW Monsoon season. It acts as a climatic divide" par excellence (Fig. I).
The changes that were first observed in May, are now emphasized and the southwesterly wind flow is now definitive and also beginning with June, gradually reaches a ceiling of over 10,000 feet and hence is not impeded at that level by the 8000 - foot central mountain chain. Thus, it is, that stations located all over the Dry Zone, even as far distant from the southwest as Jaffna, Mannar, Trincomalee and Batticaloa reflect in their anemometer - graphs, a persistent southwesterly component. However, the central mountain chain does exert orographic influence over the Monsoonal streamlines at lower levels, ie., below the 9,000 foot level. Apart from inducing orographic ascent of the streamlines as they flow against the western flanks, here is also induced strong eddy-flow at the spill-over into the easterly-located Uva Basin. This effect is of special note during the height of the monsoon, when the monsoon blowing at full strength spills over the mountain chain as a moisture - bereft wind and in descending acquires fohncharacteristics and has been designated the kachchan (13). This is experienced in July and August.
By June, then, with the establishment of the Monsoon, there is reflected everywhere in the Dry Zone, decreases in temperature. This temperature amelioration is as to be expected in the context of the strong wind incidence. Only Batticaloa and Trincomalee show slight increases (Table A. 2). Diurnal ranges again show marked effect of aspect. Thus, while the lee-location stations, viz; Badulla, Batticaloa and Trincomalee, show increases, all other stations exhibit decreases as is to be expected, with increasing cloud incidence. Again, the expected consequence of marked decreases in thunderstorm incidence and lower rainfalls, are reflected everywhere in the Dry Zone (Tables A. 4 and A. 5). Except for Hambantota and Diyatalawa, which receive about two inches, all other stations display drought effect and hence "ineffective rainfall, with most stations receiving
an inch or less (Table III).
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TABLE III.
Comparative analysis of weather changes in JUNE at selected stations in the Dry Zone.
Diurnal
Station temp. temp. Rainfall Rainy Thunderstorm
(°F) range (inches) days days
(°F)
Changes from May
Anuradhapura — 0.2 — 0.9 — 2.8 — 3 -5
Badulla — 0.5 + l. 4 — 3. l — 5 — 8(Diyatalawa)
Hamban tota - (0.2 + (0.5 - 2.2 () - 5
Jaffna - 0.2 - 0.8 - 6 - 2 -
Mannar — (0 , 6 — II . 2 — II a. 4 — 3 — 5
Puttalam — (0). 7 — II a. 6 — 2. 4 — 2 — 3
Trincomalee + (0.2 + 0.2 - 2.2 - 3 - 4
Batticaloa + 0.9 + 2.3 - 0.8 - 2 - 3
The regional pattern of rainfall distribution shows
that compared to May, the over 5 - inch belt is confined
to the southwest quadrant while the entire Dry Zone falls within the below 2 - inch region. All rainfall regimes for the Dry Zone (Fig. 1) clearly reveal the inauguration of the “drought phase' in May. This is seen to be continued until September.
In July, weather conditions demonstrated for June continue and is even accentuated, with the Monsoon in full control and reaching a consistent ceiling level. While the temperatures tend to show a decreasing trend, the diurnal ranges show noteworthy increases every where in the Dry Zone. This explains, the continuance of convectional activity, below the level of the Monsoonal streamlines. In effect in the lee location, i.e., east of the central mountain chain (Uva Basin) and along the east coast there is to be observed persistent convectional activity.
In August, generalized weather conditions are not appreciably different from those observed in July, except, that again it is the lee-location stations in the Dry Zone that stand out. Thus, these stations (Badulla, Batticaloa, Trincomalee and Diyatalawa) continue to exhibit marked diurnal ranges (Table A. 3) with increased thunderstorm
105 |

incidence. By this time, however, it is the windstream that acquires special significance. In the Northern Plain, very specifically in the Tamil-speaking area, this is the period of the inauguration of the Solaha-kachchan, which in effect is a “drying wind and of agro-climatological significance. It is, however, in the Uva Basin and the Batticaloa coastal zone — which lie to the lee of the central Highland - that the föhn wind is best developed. The author's own study of this kachchan (13) has shown, that during late July and August, this fohn wind in the Uva Basin, is comparable to such well-known examples as the Bohorok (Sumatra), the Berg (South Africa) and the Chinook (east of the Rockies in North America).
In Table IV is set out some comparable wind component percentages during the SW Monsoon period for Diyatalawa and Batticaloa. It is to be seen that westerly
TABLE IV,
Mean wind-directions (percentages) during the Southwest Monsoon period at Batticaloa (a) and Diyatalawa (b). Values shown thus (56) signify westerly - component winds.
Direction June July August September
0930 1530 0930 1530 0930 1530 0930 1530
N 3. O 3. 3 2 O 2 O NIE 2 5 O O 2 5 3 3 E 2 12 5 2. O 30 5 IO SE O 38 6 34. 13 47 7 52 (a) S 7 5 2. 16 18 13 26 12 SW 20 12 18 5 13 3 24 8 W 28 33 13 O 24. 2 19 2 NW 8 (56) 5 (50) 14 (45) 2 (17) 10 (47) 0 (5) I (50) 3 (23) Calm 10 O 19 O 19 O 7 O
N O 2 3 2 O 3 O 3 NIE O O O 6 O 5 O 2 E 13 3 3 6 14. 10 23 7 SE 8 O IO 6 23 O 13 3. (b)S 2 15 16 19 11 l 17 3 SW 12 8 18 13 8 8 3. O W IO 23 24 8 13 3. 18 25 NW 28 (50) 48 (79) 16 (58) 39 (60) lil 29 (68) 18 (39) 43 (78) Calm 17 O 10 O 19 3 7 3
All values adopted from the Colombo Observatory Reports
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Wind components in both stations show more than a 50 percent persistence. It is during this period then, that easterly wind components constitute the balance wind percentages, demonstrating that convectional activity continues to persist.
This westerly component windstream (southwesterly, Westerly and northwesterly) is obviously the SW Monsoon, which having deposited its moisture on the Windward flanks of the central Highland, spills over into the Uva Basin as a moisture-bereft dry wind. This eddy-effect, induced by the north-south trending mountain chain, results in adiabatic warming of the descending wind. Hence the föhn effect. It is seen in Table V that during the full effect of this föhn wind -- the kachchan - extremely drying conditions are imposed within the Uva Basin and even as far east as Batticaloa (more than 80 miles away). Temperatures show remarkable rise and for comparison, the mean annual and mean monthly (August) temperature values have also been included. Obviously this is a period of marked evaporation, due to “drying conditions imposed by the kachchan.
TABLE V.
Comparative analysis of temperatures (F) at Batticaloa and Diyatalawa. (a) diurnal temperatures between 3 - 12, August, (b) mean August temperatures and (c) mean annual temperatures.
Date (a) 3 4 5 6 7 8 9 10 II. I2 (b) (c)
Batticalioa 9I. 93 95 9I. 9I. 96 92 91 87 87 83.6 81. 4. Diyatalawa 72 74 77 73 74 77 78 8l 86 80 69.8 68.2
Values adopted from outstation weather reports received at the Colombo Observatory.
At Diyatalawa, the daily temperatures reveal even positive anomalies of as much as 16.2° F (86°F) while at Batticaloa it is 12.5° F (96 F). All these temperatures are as measured in the shade (Stevenson screen). From the agro-climatic standpoint, this sudden descent of the kachchan is very inimical to crops, for evapo-transpiration is very high.
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It is seen then, that the SW Monsoon season to the Dry Zone, signifies the inauguration of the drought period and hence is of vital significance for agriculture. It has already been shown that, this drought regime is not something of recent origin but has been a persistent feature of the historical climate. The vevas and kulams, which have stored the water from the NE Monsoon rains and which also utilise the SW Monsoonal rain by means of elas drawn out from the Mahaweli Ganga, provide the irrigation water so vitally needed for Yala crops. This climatological season designated the kodaikalam (Tamil: “dry season”), inaugurates the irrigated cropping-season desig
nated the Edaipokam (Tamil).
In September, the weather regime begins to reflect changes that mark the end of the SW Monsoon season. The Monsoon begins to weaken in view of its withdrawal phase and once again convectional activity begins to reassert its role in the Dry Zone. Thunderstorm incidence increases every where (Table A. 5) and diurnal ranges also show slight increases. The number of rainy days increase and so does the rainfall. This is reflected in the rainfall graphs (Fig. 1) and rainfall gradually becomes “effective for agriculture.
TABLE VI
Rainfall changes in September in the Dry Zone
Station Rainfall in Change from August
September (ins.) rainfall (ins.)
Anuradhapura 3. 8 + 1.6 Badulla 4.5 + 1.3 Batticaloa 2.3 + 0.3 Hamban tota 2.8 + 1.3 Jaffna 2.5 + 1.4 Puttalam 1.6 + 1.0
The regional rainfall pattern (Fig. 2) reveals the occurrence of two arid zones in the northwest (Mannar-Puttalam -Jaffna environs) and a smaller area in the southeast (YalaKirinda environs). As Would be natural to expect, the over 12 - inch rainfall zone is confined to the Wet Zone/
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Dry Zone boundary and rainfall decreases northwestwards and southeastwards. Rainfall is naturally ineffective for agriculture and everywhere cropping is irrigation-based, even in the transitional Zone.
(d) The (autumnal Convergence - Convectional - Cyclo
nic season (October - November).
By October, new atmospheric conditions get to be established over the island and it is the Dry Zone that is immediately distinctly affected. This is the period of the seasonal wind-change, namely the transitional phase between the withdrawal of the southwesterly streamline and the setting-in gradually of the northeasterly streamline. In the Indian sub-continent, with the SW monsoon withdrawal in September, already the so-called Northeast Monsoon has established itself. In effect, this is the hemisphereic Trades - the Northeast Trades. It has already been pointed out, that the seemingly Monsoonal characteristics of heavy rainfall associated with this season, is due to the circumstancial combination of a number of atmospheric conditions (9).
In keeping with the seasonal “return of the Sun to the southern hemisphere, the ITCZ which lies athwart the thermal equator also migrates similarly, and makes its seasonal passage over the island. Convergence weather is then expected to prevail over Ceylon in October and November. At the same time this is also the period of convectional activity and it is only when the ITCZ. prevails that the normal afternoon thunderstorm rhythm is disturbed and the island experiences all - day drizzle and rain. Sudden weather deterioration is then experienced only when the ITCZ. boundary, viz., the Northern Convergence Zone (NCZ), crosses the island. During such a crossing, it is very probable that “frontal characteristics develop, consequent upon the convergence of the warm Equatorial Air Mass and the relatively “colder' northern hemispheric Air Mass. This season, then, is also one of marked cyclonic incidence. It has been shown (16), that nearly fifty percent (50%) of cyclonic storms experienced in the island since 1845, was confined to the October - November months. Some of these
storms have been responsible for noteworthy 24 - hour rainfalls; constituting almost fifty percent of the mean annual rainfall.
109

TABLE VII.
Rainfall incident upon cyclonic storms
Rainfall in Mean annual
Station Date 24 hours (inches) Rainfall (inches)
Jaffna Nov. 17, 1918 20.48 53.00 Chavakachcheri Nov. II, 5, 1939 2.7 56.00 Jaffna College
(Vaddukoddai) Nov. 15, 1939 5.00 55.00
These triple-meteorologic circumstances - convergence - convection - cyclonic - then are responsible for the notable heavier rainfalls that are experienced in the Dry Zone during this season compared even to the total SW Monsoonal rainfall of four months. It is also noteworthy, that the annual rainfalls exhibit negative anomalies, in those years, when the expected cyclonic incidence during this period, has been totally absent. It is now accepted that the heavy rainfall incidence during this season, is not truly “monsoonal, but is related closely to depressional or cyclonic activity. During non-cyclonic incident years, the seasonal rainfall is conditioned by convectional activity and the passage of the
NCZ and generalized ITCZ dominancy.
By October, with the island now coming within the seasonal hemispheric winter, temperatures show appreciable fall everywhere in the Dry Zone, the lesser falls being observable in the Upland Zone (Table A. 2 and Table VIII). Hamban tota, in view of its location near the transitional zone (Fig. 1) naturally also reflects a smaller change from the SW Monsoon months. Except for small positive changes in Hamban tota, Jaffna, Mannar and Puttalam, diurnal ranges show negative changes in the Dry Zone. This is as to be expected with the increasing cloud cover. Nevertheless, thunderstorm incidence show increases every where, for convectional circulation also is operative during this season. It is to be noted, that as is to be expected, thunder incidence decreases slightly in November, while October with less tendency for cyclonic incidence, naturally exhibits high thunderstorm frequency. This explains the negative
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|- *:|-•• *:( o TABLE VIII.
Comparative weather rhythm for Dry Zone Stations in October and November. (All figures
shown within () relate to changes from the monthimmediately preceeding, e. g., September and October respectively. Temperature values in oF and rainfall ininches.) StationOCTOBERNOVEMBER abCdeabo ede Anuradhapura81.2 15.39.6161078.6 11.3 10.7198 (-2.0) (-1.2) (+5.8) (+9)(+5)(-2.6) (-4.0) (+1.1) (#3)(–2) Badulla74.217. 49,02214歌72. 413. 410. 22112部 (-0.8) (−4.1) (†4.5) (#3) (+5)(-1.8) (−4.0) (+1.2) (–1) (-2) Batticaloa81.211.87.2|18979.29.713. 8205 (-1.8) (-1.9) (†4.9) (†5)(十3)(-2.0) (-2.1) († 6.6) (#2)(–4) Hambantota80.810.94.813979.611. 27.51610 (-0.5)(于0.5)(于2.0)(十4)(于6)(-1.2) (+0.3) (#2.7) (#3)(+1) Jaffna81.68. 29.212679.29.010.5185 (-1.0) († 1. 1) (†6.7) (#8) (#3)(-2.4) (†0.8) (#1.3) (+6) (-1) Puttalam79.510. 67.514679. 4.12. 110.1185 (-2.7) (+0.7) (†5.9) (+8)(+4)(-0.1) (+0.5) (†2.6) (+4)(–1) a = mean monthly temperature ; b = mean diurnal range ; c = mean monthly rainfall d = Rainy - days ; e = Thunderstorm days ; * Diyatalawa
II.

changes (Table VIII) observed in November, in practically all the Dry Zone stations.
It is to be noted that in November, all stations continue to show rainfall increases, but that only Hambantota exhibits some increase in the thunderstorm days. Being far removed from the incidence of the early monsoonal streamlines, this station naturally is under the stronger influence of convectional activity. The total number of “rainy days' is very high, with most stations reflecting a 16 - day to a 21day incidence. The continuing rainfall increases may be attributed to increasing cyclonic or even slightly depressional effect.
It is indeed noteworthy that the October - November rainfall of only two months is far in excess of the total four-monthly SW Monsoon seasonal rainfall, some of the excesses being as much fourteen to sixteen inches, which in effect constitute between two hundred to five hundred percent excess. Thus, it is to be noted (Table IX) that the 14 - inch excess in Mannar is in effect nearly a five hundred percent increase over the SW Monsoon total rainfall of only 2.7 inches. The regional rainfall pattern reveals that for the Dry Zone, this is the heaviest rainfall season for a number of stations, including Jaffna, Diyatalawa, Hambantota, Mannar and Puttalam. In November, it is only the Hambantota - Yala - Kirinde Zone, that receives less than 10 inches, while the rainfall is widespread, with concentrations indicative of orographic uplift. From the agro-climatic standpoint, rainfall become effective during this season.
These months, constituting the “transitional season from one Monsoon to the other, does naturally reflect in its regional pattern no concentration - Zones, for cyclonic incidence often induces heavy rain over a wide area. The general trajectory of tropical storms is from the southeast (near Batticaloa) towards the northwest coast (near Mannar. The year to year rainfall then, during this season, tends to be highly variable and this aspect will be considered later (Fig. 3).
(e) The Northeast Monsoon Season (December –
February).
By December, the northeasterly streamline is well established over the island and in the local context, the
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TABLE IX.
Comparative rainfall analysis between the SW Monsoon season and the Convectional - Convergence - Cyclonic season, at selected Dry Zone stations. (all values in inches).
Station SW Monsoon October - Now. Change Percent
rainfall rainfall (approx.)
Anuradhapura 7. A 9.6 + 2.2 29 Badulla ... 5 9.2 + 7.7 67 Hamban tota 0.5 2.3 + I.8 II. Jaffna 4.5 I9.7 + 15.2 350 Mannar 2.7 6, 7 + 14. () 50 Batticaloa 22. O + 15.7 250
NE Monsoon is then said to be in control over Ceylon's climatic regime. It has already been pointed out that the NE Monsoon is in effect a mis nomer to this normal, seasonal hemispheric Northeast Trades (9). This so called NE Monsoon is in no way a counterpart of the SW Monsoon, from any consideration. There is no dynamic changes effected in the wind stream, the rainfall is highly conditioned by the incidence of cyclonic incursions during the prevalence of the NE streamline, the wind strength is very much lower than that of the SW Monsoon and the “depth of the Monsoon during this season is very much lower than that of the SW Monsoon. Some degree of quasi-monsoonal or semi-monsoonal characteristics are, however, acquired by the Trades from the wind-flow from the Kashnir - Jammu High which reaches the Bay of Bengal down the Ganges gradient The “surges' experienced during the NE Monsoon, has been traced either to these quasi-monsoonal flow from NW India or to the occasional polar outbreaks (9) that enter the Monsoonal parameter through the Brahmaputra gap.
In the Dry Zone, temperatures naturally continue to exhibit decreases from the November values. Often it is, that low temperatures bringing in cold spells are experienced in the Northern Lowland, as far south as Anuradhapura and even to Matale, consequent upon the occasional polar outbursts' referred to earlier (10). In view of the decreasing temperatures, rainfall becomes “effective for agriculture.
13

Since the northeasterly streamline is in full control, it is natural that diurnal temperature ranges must show decreases and this is best seen in respect of stations that are located with easterly “exposure”, viz., Badulla, Batticaloa and Trincomalee. Other Dry Zone stations that are either in 'sheltered or “distant locations, reflect a slight increase
in diurnal ranges, viz. Jaffna, Puttalam, Hambantota and Anuradhapura (Table X).
Thunder days are at a minimum everywhere, with only Badulla and Hamban tota (with 5 and 6 days respectively) which in themselves are appreciable decreases compared to November. Convectional activity is now at a minimum. Rainfall shows interesting features, with decreases everywhere in the Dry Zone except at Batticaloa and Trincomalee (Table A. 4) and to some degree at Badulla. Though statistically the rainy-days in December are seen to show a decrease (Table X) yet in effect, these days of rain are appreciable, with most stations having more than half the month with a minimum fall of 0.01 inch.
The regional pattern of December rainfall, exhibits a southeast — northwest aligned concentration, with a certain degree of orographic-induced falls. But, as during the previous season, it is the incidence of cyclonic storms that condition the year to year rainfall in the Dry Zone, during this NE Monsoon season. Heavy twenty-four hour rainfalls, have been recorded and equal to nearly fifty percent of the mean monthly totals. Both December and January are
cyclonic months, while occasional depressions have appreciably increased February rainfall.
The regional rainfall pattern in January, is similar to that of December, except for the lower rainfall; it is the initial “uplift of the low level streamline which was responsible for the higher falls in December. In January again, as in December, it is the incidence of depressional activity that conditions the year to year rainfall. With the monsoonal ceiling now at a higher level it is only adequate orographic lifting that can induce the otherwise dry Trade-wind to precipitate its acquired moisture. The southeast-northeast aligned rainfall belt is still dominant, while in the northwestern and western coastal zone of the Dry Zone, the rainfall is below five inches (Table A. 4), with Mannar (3.9
14
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^!*|-! s^, , o o,
TABLE X.
Weather changes since November at selected Dry Zone Stations during December.
(Changes shown thus: (); temperature values in degrees fahrenheit and rainfall in inches.)
|-
DECEMBER
Station#"Rainfall露* Anuradhapura76.6 ( — 2.0)13.0 (+1.7)5.7 (– 5.0)16 ( – 3)2 (–6) Badulla70.6 ( — 1.8) 12.4 ( — 1.0) 11.5 (+ 1.3)21 ( — 1)5 ( – 7) Batticaloa77.7 (-1.5)8. 4 ( — 1.3). 17.0 ( + 3.2)20 (+2)3 ( — 2) Hambantota78.8 (-0.8)11. 7 (+0.5)5.7 (– I.8)13 (–3)6 (–4) Jaffna77.6 ( — 1.6)9.5 (+0.5) 10.4 (-0.1)14 (– 4)2 ( – 3) Puttalam78.0 (-1.4). 13.6 (+ 1.5) 5.5 (-4.6)13 (–5)2 ( – 3)
115

TABLE XI.
Daily rainfalls during December and associated with cyclones,
24-hours mean December Station Date rainfall rainfall (inches) (inches)
Kannukeni Dec. 19, 1911 20.00 58. 27 Mullaitivu Dec. 18, 1911 3.18 6.94. Nedunkeni Dec. II, 5, 1897 3. 72 66.52 Amparai Tank Dec. 7, 1881 I9. 20 72. 30 Diwulana Tank Dec. 8, 1884 1950 79.30
inches), Jaffna (4.4 inches) and Puttalam (3.4 inches). Hambantota in the south, is the other Dry Zone station with less than 5 inches (4.0 inches).
February, is a “dry” month and is certainly the driest month for the entire island. In the Dry Zone, however, rainfall is appreciably more than during SW Monsoonal months and even some heavy falls may be experienced, due to an occasional cyclone. Monthly temperatures are only slightly on the increase but diurnal ranges have increased, as expected, in view of the cloudless days (Table A. 3).
The NE Monsoonal season, is in a sense the climatological counterpart of the SW Monsoonal season, as far as the Dry Zone is concerned. The seasonal rainfall pattern (Fig. 2) reveals a general “wetter eastern zone (over 20 inches) and a “drier western zone (10–20 inches). The highest amounts are closely related to the Knuckles orographic zone and is confined to the Western boundary of the Dry Zone.
This season, then, with the setting-in of the Vadai (Tamil: “northerly winds") inaugurates the important agricultural season of the Kalapokam (Tamil). The Marikalam (Tamil: “wet season”) is the eagerly looked-for period in the Northern Lowland, after the dry and scorching solagam “dry monsoon”. Already, the early November rains has
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heralded the Vasanthakalam, which marks the change from the irrigation-fed to the rain-fed cropping season.
SEASONAL RHYTHM
It has been demonstrated that in the Dry Zone, the Weather regime, does exhibit a definite rhythm, mainly correlated to the incidence of rainfall. While temperatures both monthly mean and diurnal ranges-do reflect a seasonal sequence, they do not vary very much, so as to condition agricultural activities. It has already been suggested earlier, that in the Dry Zone may be indentified, a dual zone on a thermal basis, namely by and large the dominant LOWLAND ZONE and a secondary yet important UPLAND ZONE (Fig. 1). During the analysis of the seasonal climatic regime, it was evident that the Upland Zone did reflect its own characteristics in such considerations as a regionalized temperature zone and that diurnal ranges often exhibited changes opposite to those exhibited by lowland stations. The topographic character also induces other “micro-climatic conditions, even so far as to affect even as large an area as the Uva Basin. The Kachchan was cited as being of direct effect to the lee-located depressional zone, east of the central mountain chain.
However, it is in the reversal conditions of rainfall incidence during the two dominant seasons — the SW Monsoon period and the NE Monsoon period — that the raison d’etre is sought for the agricultural structure of the Dry Zone. Thus in effect, an over-generalized, over-simplified and even an easily recognizable irrigation-fed cropping season during the long drought period and a rain-fed cropping season during the major “rainy period. It is seen from Table XII that the major portion of the Dry Zone receives hardly 20 percent of its annual rainfall during the drought period from June to September; Hambantota which lies close to the southern boundary (Dry Zone / Wet Zone) alone receives a 25 percent incidence during this season. On the other hand, it is to be noted, that all Dry Zone stations receive upwards of 25 percent of the annual total rainfall, from the NE Monsoon - period rains, A further examination of Table XII clearly demonstrates the transitional features of the rainfall climate of Puttalan and Hambantota, for the excess of NE Monsoon rainfall
II 7
";

ܠܓ
TABLE XII.
Comparative Analysis of Monsoonal Rainfall in the Dry Zone. (All values in inches. Based on the 1881-1950 data).
a. b C d e f Station SW Mon- annual a as % NE Mon- d as %
soonal rainfall of b soonal of b d - a rainfall (approx.) rainfall (approx.)
Anuradhapura 7.4 55.85 12.5 24.2 43. + 16.8
Badulla II.5 72.28 7.0 25.0 35. -- 13.5
Battica Joa 6.3 65.52 9.0 33.9 55. + 27.6
O
O
O
Trinco malee 9.8 65.62 15.0 24.0 36.0 + 14.2
Hamban tota | 0.5 40.50 25. 0 II . 2 28. 0 -- 0. 7
Jaffna 4.. 5 5II . 75 J. 0. 0 16. 3 35. 0 + I.I. 8
O
O
十10.7 +5.7
Mannar 2. 7 39.65 7.5 3.4, 33. Puttalam 4.6 44.26 (), () 10.3 25.
over the SW Monsoon raintall, is less than 10 percent only in these two stations. All other stations reveal excesses of between approximately 150 percent and 500 percent. But it was also shown that it is during this high-rainfall period, that the year to year amount is conditioned by the incidence of cyclonic activity. Often it is, that the failure of the NE Monsoon rains, coincides with marked absence of cyclonic incidence. It is necessary therefore to examine the nature of reliability of the seasonal rainfall incidence.
RAIN FALL RELIABILITY IN THE DRY ZONE
One of the major hazards in Tropical agriculture is the factor of rainfall variability. Often it is that critical rainfall limits are adopted for agrarian purposes. It is also observed that there occurs a high degree of variance from year to year, from this vitally important statistical measure. It has also been suggested that “agriculture in the lindian area is a gamble in the monsoon'; time and again, the monsoon has “failed either to appear on time or to produce the rainfall amount that is expected of it.
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Considerations of assessing the reliability of such a highly variant factor as Monsoon rainfall, must be made in the context of two aspects. There is first, the aspect of adopting a satisfactory statistical central measure for the computation of the average statistic. The common practice of adopting the arithmetic mean, especially when such a mean is computed from a short-period data, is pregnant with too much simplification so as to become almost of little significance. It has been pointed out with reference to agriculture in Ceylon (17) that the adoption of the arithmetic mean based on the 1911-1940 rainfall data is very un satisfactory from the agro-climatological standpoint. Recent research (II) has conclusively proved that this period is made up of two decades of wet phases and a single “dry phase'. This near s that the arithmetic mean so computed, is already positively-weighted and hence all critical values are also positively — weighted. Other central measures of dispersion are available and may be adopted (21).
The second aspect is that of seasonal variation, i. e., year to year as well as that of “secular fluctuations'. Detailed considerations have already been made elsewhere (ll, lS) to this very important aspect. It may suffice here to point out the significant features. In the adoption of the arithmetic mean for use as critical limits in agriculture, the aspect of variability must also be embodied. For, any single year's value is bound to vary considerably from the adopted mean. The usual practice is to adopt four easily computable measures of variability, viz., the mean deviation (absolute value), the standard deviation (absolute value), the relative variability (percent value) and the variability coefficient (percent value). In this investigation, the first two measures have been used to demonstrate the significance of the factor of variability in the Dry Zone rainfall climate.
In Figure 3, two maps have been prepared showing the degree of rainfall variability that is to be expected in the Dry Zone, on an annual consideration. It is seen in Map A, that the greatest variations occur along the landward boundary of the Dry Zone and also along a coastal belt extending from Batticaloa to north of Trincomalee. These
are areas of high rainfall (Table A. 4 and Table XIII: viz.,
19

ܠܢ
Badulla, Batticaloa, Trincomalee, Negombo). It is natural, that such stations would reflect high absolute deviation values, ranging from between ten and fourteen inches.
TABLE XII.
Mean Deviations (inches) and Relative Variability (percent) of Annual Rainfall at Selected Stations in the Dry Zone of Ceylon.
Deviation values computed from the long period mean,
1881-1950.
Mean Mean Relative
Station Annual Rainfall Deviation Variability
(inches) (inches) (percent)
I. Allai Tank 7.80 2.79 7.80 2. Anuradhapura 55.85 8.05 4.3. 3. Badulla 72. 28 2. 77 17, 70
4. Batticaloa 65.52 9.6 4.65 5. Chadaiyan talavai 65.60 3.3 20. 27 6. Dambulla 63.9 () 12., ()6 18.93 7. Hamban tota 40.50 7.00 7.28
8. Jaffna 51. 75 II. 69 22.63 9. Kantalai Tank 7.89 88 6.55 10. Mannar 39.65 7.4 8.68 11. Negombo 73. O2 2. 32 6.84. I 2. Puttalam 44.26 7.09 I5.82 13. Rukam Tank 75. 49 13. 60 8. O. 4. Sakamam Tank 63.08 II. 83 8. 70
I5. Tissamaharama 40. O. 6.85 7.00
16. Trincomalee 65.62 0.40 5.85
Data collected from manuscript records at the Colombo Observatory (1881-1924) and from the Colombo Observatory Reports (1925-1950)
On the other hand, the low deviation values (absolute amount) are seen to be confined to areas of low rainfall, viz., Mannar, Puttalam, Hambantota and Tissamaharama,
with each station reflecting values around only seven inches. The use of this map alone would give a picture that is not
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truly of significance and also one that can be quite misleading. It is necessary therefore to provide a complementary map and this is seen in the rainfall variability map (Fig. 3, B). Here the mean deviation value (inches) is expressed as a percent of the annual total rainfall of the respective station. An examination of Table XIII, now provides an entirely : different picture, for the originally low-value stations now exhibit high values (percent). Mannar, which orginally had a low deviation-value of 7.4 inches now exhibits a very high relative variability value of nearly 19 percent. The corresponding map (Fig. 3. B) now shows the reverse effect, namely, that low deviation — value areas now appear as high variability areas. However, it is also to be observed, that some high deviation value stations, viz., Jaffna, Chadaiyantal avai (west of Batticaloa), Allai Tank (south of Trincomalee) also exhibit high relative variability values. This may be explained in the context of these stations being located within the belts of cyclonic trajectory. It is clear, then, that the factor of rainfall variability in the Dry Zone, must be reckoned with, in attempting to define critical limits of crops. Investigations into the variability factor in respect of seasonal rainfall incidence would prove of تر immense value, especially if correlated with probability values. It is also seen that the year to year, Southwest Monsoonal rainfall at Hamban tota, conditions the salt harvest (22).
Yet another aspect of variability that has been given hardly any consideration, is that of secular variability. The author's own researches have demonstrated that statistically such secular fluctuations' especially in the rainfall climate of the Dry Zone, has been real and have even been provided sufficiently tenable physical reasoning. The twenty year wet-dry phase-pattern has been observed not only for Ceylon (II) but also within the tropical zone (20). This means that 20 - year periodicities of 'wet' and “dry” rainfall
phases, are superimposed upon the year to year variations. This may be summaries d as :-
Up to 1880: Dry Phase I 188 - 1900: Wet Phase I ܕܠ
1901 – 1920: Dry Phase II
1921 - 1940: Wet Phase II 1941 - 1960: Dry Phase III (?) 1960 - ? Wet Phase (?) III (?)
2.

The exact dates of phase changes are not coincident with the decadal dates but are approximately about 1903, 1923, 1946 (ll). The seasonal phase - periods are almost coincident with the annual periodicities of 20 years.
CLIMATIC REGIONS OF THE DRY ZONE
The investigation of the climatology of any area must finally envisage the ecognizance and demarcation of climatic regions. In view of the overall significance of the prolonged drought period coincident with the SW Monsoonal season, the tendency has been to oversimplify the climatic theme of this vital area and hence also to assign the Dry Zone a single climatic designation. It has already been demonstrated, that from the temperature standpoint, two distinct “thermal regions may be identified, viz., the Dry Zone Lowland and the Dry Zone Upland. These are climatic regions, which are not only characterised by temperature value differences but also find substantiation in the biota expression. Apart from these regions, in view of the demonstrated variation in rainfall incidence -- both in amounts and in seasonal concentration - isohyetal zones or rainfall regions may also be truly recognized and demarcated in this assumed single climatic Zone.
The author's own attempts to arrive at an adequate identification and demarcation of the climatic regions will eventually appear in a research paper. However, some pointers to such demarcation, have been made already (6). Subsequently, in later years, the author has attempted to recognize for the island, climatic regions based on the application of the well known Köppen (8, 18) and Thornthwaite (8) climatic classifications. In these attempts, it was brought out that “modifications were necessary in their application to an island like Ceylon, in the context of its dinnension and local features. Thus, it is, that the maps appearing in Figure 4, exhibit the identification of regions much different from those in the map, incorporating the strict Köppen classification (8).
According to the original Köppen classification (3a), no part of the Dry Zone, would be categorized under the Dry Climate, viz., the B climate. However, the author’s own investigation of the two areas in the northwest (Mannar
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environs) and in the southeast (Yala - Kirinda - Hamban tota zone) have clearly revealed that the vegetation of these areas are strongly correlative to the vegetation of true B climates in the United States (i. e., based on author's own field investigation in the Mohave Desert, California). Thus, it is, that (Fig. 4a) these zones have been designated BSh, viz., Semi-Arid (hot) climate. Similarly, other modifications have been suggested (18) and incorporated in Figure 4, namely, the sub-climates of the A Zone (Rainy climate). These have been based on seasonal variation of rainfall and with special emphasis on the monsoonal rainfall concentration. Thus, the identification of the Ams, Amsi, Amw’i, Asi, As w” and Asw’i in the Dry Zone. The Upland Zone is categorized under the Csbi climatic region, i. e., Humid Mesothermal.
Similarly, the application of the strict Thornthwaite classification (23) shows that further modifications are necessary when applying this scheme to Ceylon (8). Five climatic regions were identified (Figure 4b), viz., BA’r (Humid Tropical), BA’s (Humid Tropical with marked dry season), BB'r (Humid Mesothermal), CA’r (Sub - Humid Tropical) and CA's (Sub - Humid tropical with marked dry season). These regions when considered with the climatic regimes of the respective zones in the Dry Zone, are inadequately representative of their true climates. Hence, the author's attempt to apply the later Thornthwaite classification (24) which provides for more realistic climatic zones on the basis of potential evapotranspiration. Even here modifications are necessary in the context of the local climatic themes as will be shown in a research paper (to appear in the Tropical Agriculturist).
An adequate presentation of the climatic regions, not only of the Dry Zone, hut of the entire island, is most essential, in the context of the island's agrarian economy. Such a classification must try and aim at incorporating the agro bias and hence justify the designation of agro - climatic regions.
BIBLOGRAPHY
(l) Farmer, B. H. - “Peasant Colonization in Ceylon, Pacific
Affairs, vol. 25 (1952), pp. 389-398.
(2) Hydrometeorology of Ceylon - Parts I and II (Canada
-Ceylon Colombo Plan Project, 1962).
23
 

(3) Knoa, Robert. - A Historical Relation of Ceylon. (1681).
(3a) Köppen, W – “Das Geographische System der Klimate,
in Vol. 1 of Köppen and Geiger: Handbuch der Klimatologie (Berlin: Gebruder, 1936).
(4) Mahavansa - (transl. W. Geiger, 1912).
(5) Toynbee, A. - A Study of History (Oxford Univ. Press,
1934), Vol. II, p. 5.
(6) Thambyahpillay, G, - “Climates of Ceylon” (M. A. Thesis:
Univ. of California, 1952), 295 pp.
(7) Thambyahpillay, G. -- “Ceylon and the World Climatic Mosaic, University Ceylon Review Vol. XIII, 1 (Jany. 1954), pp. 24—54.
(8) Thambyahpillay, G, - “Thunderstorm Phenomena in Ceylon,' Univ. Cey. Rev. Vol. XIII, 3 (July, 1954, pp.
64 - 76.
(9) Thambyahpillay, G, - The Rainfall Rhythm in Ceylon
(1955), 52 pp.
(10) Thambyahpillay, G, - “The Thermal Factor in Ceylon's Climate.” Univ. Cey. Rev, Vol. XIII, 2-3 (Apr., 1955), pp. 83–112.
(II) Thambyahpillay, G, - Climatic Changes in Ceylon (Ph. D Thesis: Univ. of Cambridge, 1958), Vols. I, III and III.
(12) Thambyahpillay, G. - “The Investigations of Climatic Fluctuations,” Ceylon Geographer, Vol. 12, 1-2 (Jany. - June, 1958, pp. 25–30.
(13) Thambyahpillay, G. - “The Kachchan - A Fohn Wind in Ceylon.” Weather (Royal Net. Soc.), Vol. XIII, 4 (April, 1958), pp. 107—114.
(4) Thambyahpillay, G, - “Secular Fluctuations in the Rainfall Climate of Colombo,” Univ. Cey. Rev. Vol. XVI, 3-4 (July - Oct., 1958), pp. 93-106.
(15) Thambyahpillay, G, - “The Rainfall Fluctuations in Ceylon.” Ceylon Geographer, Vol. 12, 3-4 (July - Oct, 1958), рр. 51—73.
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(16) Thambyahpillay, G, - “Tropical Cyclones and the Climate of Ceylon.” Univ. Cey. Rev., Vol. XVII, 3–4 (July–Oct. 1959), pp. 137—180. (17) Thambyahpillay, G, — “Agro - Climatological Significance of Rainfall Variability in Ceylon.” Agriculture, Vol. 3 (1960), pp. 13—27. (18) Thambyahpillay, G, - “Climatic Regions of Ceylon,' Trop.
Agriculturist, Vol. CXVI, 3 (Sept., 1960), pp. 1-31. (19) Thambyahpillay, G, — “Burst of the SW Monsoon.” Ceylon Geographer, Vol. l4, l-4 (Jany.-Dec., l960), pp. 31—54.
(20) Thambyahpillay, G. -- “Climatic Changes within the Inter-Tropical Convergence Zone,” Paper read at the Asian Geographers' Conference (Kuala Lumpur, Malaysia, 1962).
(21) Thambyahpillay, G. - “Mathematical aids to Climatological Research in Ceylon Mathematica (1963), pp. 42–5l.
(22) Thambyahpillay, G, - “Salt Industry of Ceylon, Jour. Hist, Soc. Studies, Vol. 7, I (Jany.-June, 1964), pp. 73–87.
(23) Thornthwaite, C. W., - “The Climates of North America according to a New Classification,” Geographical Review, Vol. XXI (Oct., 1931), pp. 633-652.
(24) Thornthwaite, C. W., - “An Approach Toward a Rational Classification of Climate,” Geographical Rev., Vol. XXXVIII (Jany., 1948), pp. 55-94.
A P P E N D X
TABLE A. I. - DRY ZONE CLIMATOLOGICAL STATIONS
h AMAN AMA ight la an 4. . , ור Station 蠶 S. l. Aspect Rainfall TME". (inches) ture (F) (1911-1940) Anuradhapura 295 Inland Lowland 56.9 80. 9 Badulla . 22:25 Inland Upland 72.0 73.5 Batticaloa 26 (E) Coastal Lowland 69.0 81.4 Diyatalawa 4.04 Inland Upland 65.6 68.2 Hambantota 6. (S) Coastal Lowland 43.3 80. 7 Jaffna 14 (N) Coastal Lowland 53. 81 .. 5 Mannar 12 (W) Coastal Lowland 39.7 82. Puttalam 27 (W) Coastal Lowland 43.5 81.0 Trincomalee 24 (E) Coastal Lowland 64 - 8 82.
125

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Page 81
TABLE A. 3.
-
|-Dry ZoneClimatological Stations : MeanMonthly Diurnal Temperature Ranges. (°F)
----
sæ-æ−========–_ Station Jan. Feb. Mar. Apr. May June JulyAug. Sept. Oct.Nov. Dec. Range Year
sæ
•=
|--•=
Anuradhapura 14.2 17.3 19.3 16.8 14.2 13.3 15.0 16.0 16.5 15.3II (313.0 6.3 15.4
Badulla12.8 15.0 17.9 17.8 18.6 20.0 22.3 21.8 21.5 17.4 13.4 12.4 9.917.6 Batticaloa8.0 9.1 10.3 11. I 12.3 14.6 15.4 14.0 13.7 11.8 9.7 3.4 7.411.5 |-Diyatalawa14.7 18.0 19.1 17.4 16.5 14.5 15.7 16.4 17. I 15.6 13.9 13.8 5.3 16. I
Hambantota12.4 12.9 12.5 11.3 9.1 9.6 11.4 11.8 10.4 10.9 11.2 11.7 3.3 11.9
Jaffna 11.0 13.2 12.7 9.4 6.5 5.7 6.2 6.7 7.1 8.2 9.0 9.5 7.5 g. 3 Mannar9.2 12.6 14.3 12.5 8.9 7.7 8.4 8.9 9.1 9.7 8.9 8.0 5.9 9.9 Þuttalam15.6 18.1 16.8 13.2 9.4 7.0 7.5 8.4 8.9 10.6 12. I 13.6 II. I 11.8
Trincomalee5.5 6.7 9.0 11.4 12.9 13. I 14.3 14.9 14.9 12.2 8.6 6.9 9.4 10. g
ææ
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|-- Highest and lowest values inheavy type.
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TABLE A. 5. Thunderstorm incidence (days) in the Dry Zone (1931 – 1950)
■
Jan. Feb. Mar. Apr. May. June July Aug. Sept. Oct. Nov. Dec. Year
...
Anuradhapura1 1 7 14 6 1 2 4 5 10 8 2 61 Batticaloa1 3 3 8 8 5 4 6 6 9 5 3 61 Diyalalawa2 3 10 18 12 4 5 9 9 14 12 5 99 Hambantota2 3 10 14 7 2 1 1 3 9 10 6 68 Jaffna0 0 2 7 4 1 1 2 3 6 5 2 33 Mannar1 1 8 13 6 1 1 3 5 10 9 2 60 Puttalam1 2 6 8 3 0 0 1 2 6 5 2 36 TrincomaleeI m 3 , & 3 %, , , mm , 3 없
Highest and lowest values in heavy type.- -
|-
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Page 83
PHOSPHORUS NUTRITION OF THE
RICE PLANT.
| S. T. SENE WIRATINE
OME of the physiological aspects of phosphorus nutrition have been investigated. Mitsui (II) has shown that the partial efficiency of P205 was greatest during the early stages of growth. These results obtained by using solution culture techniques have been confirmed in pot experiments. Foliar symptoms of phosphorus deficiency have been described by Aiyer (2). He found deficient plants to be stunted, with small dark green or blue green leaves bunched together at the top. It was also noticed that such plants failed to reach maturity. Recent work by Mitsui has linked phosphorus uptake with oxidative phosphorylation (3).
The work done on soil phosphorus in relation to rice culture is more impressive. Aoki (4) has worked on the availability of soil phosphorus to plants under both aerobic and anaerobic soil conditions. He has demonstrated that solubility of P205 is largely dependent on pH, and that phosphate availability was greater under flooded soil conditions. It has also been suggested that the reducing conditions occuring in a flooded soil increase with time. This increase has been associated with a correspondingly greater release of phosphorus to the plant. This view has been put forward in support of the general observation that rice yields are greatest, when phosphate applications are given as basic dressings rather than as top dressings. It is visualized that the basic dressings of phosphorus compensate for the relatively poor availability of phosphorus in the early stages of growth. (I).
The investigations reported in this paper attempt to
explain the nature of phosphorus uptake and the various phosphorus nitrogen relationships.
3.

PHOSPHORUS UPTAKE
Data obtained from tissue analysis indicates that leaves accumulate phosphorus and translocate the element out with the onset of senescence (Table 1). The behaviour of phosphorus in the culm tissue is identical. The seasonal variation in the phosphorus content in the grain shows a gradual increase in phosphorus, to be followed by a sudden rise during the last month. This accumulation is the result of translocation of phosphorus from other tissues rather than the result of increased uptake as can be seen from table 1. About 75% of the total phosphorus taken up is finally located in the grain.
TABLE
Seasonal Changes in Phosphorus Content of Entire Plants
Age of Mg. P per plant plants in days Leaves Culm Grain Roots Total
46 (). 883 0.059 - 0.75 II 7
67 5, 200 0.387 - 0.49 6.078
88 2.39 2.687 -- 0.49 15.569
()2 II. I 59 || 4.876 || 0.377 || 0.528 6.940
23 0.38 9.938 5.969 0. 600 26.888
49 5,047 I. 953 22.907 0.525 30.432
60 3. 807 2.253 26.02 . (). 225 32.297
The more interesting aspect of phosphorus uptake, is the general pattern of accumulation as related to the physiological changes that occur in the plant. From germination to the initiation of flower primordia the total phosphorus taken up amounts to only about 20% of the final quantity assimilated. From this time on, there is a marked increase in the rate of uptake and at floral exertion the plant has accumulated nearly 65% of its total needs. The balance 35% is taken up during the filling and maturity of the grain. It is evident that this relationship does not follow the pattern of either nitrogen or potassium accumulation (5, 6).
32

Page 84
It is also interesting to note that phosphorus uptake is quite slow at the inception and that rapid accumulation actually occurs only half way through the growing period. This small requirement of phosphorus during the early stages of growth does not appear to substantiate the explanation offered for the high yields obtained from basic dressing of phosphate fertilizer, namely that the basic applications supplemented an inadequate supply, during the early stages of growth.
LUXURY CONSUMEPTION OF PHOSPHORUS
Solution culture studies have indicated, that no increase in vegetative growth occured when the concentration of phosphorus exceeded II p. p. m. in the culture media. This has been found to be true when the plant is supplied with either nitrate or ammonium nitrogen as its source of nitrogen (Table 2). However tissue analysis of these solution culture grown plants, did indicate that luxury consumption of phosphorus was possible, when the solution culture was supplied with over 1 p. p. m. phosphorus. Thus, after the phosphorus levels required for growth are once met, no further growth responses appear to be made, but luxury consumption could occur.
TABLE 2.
The effect of varying phosphorus levels on plant weight and phosphorus composition of plants.
(Results from solution culture experiment)
Dry Weight in Grams % P in plants
added to
NH NO INHI NO culture c. Càfie C. (NÏ
O 4. 24. 4. 20 0.067 0.073
0. 6.34 6.82 0.089 0.089
0.5 8.48 II. 40 0.97 0.43
II . 0 9.44 14. 20 0.320 0.225
2.0 8.64 3.22. 0.486 0.368
3.0 7.52 2.90 0. 553 0. 508
33

Z
PHOSPHORUS-NITRO GEN INTER RELATIONS
The data discussed below was obtained from a field experiment, where ammonium sulphate and super phosphate were drilled into the soil at the rates of 40 and 60 lbs. nitrogen and 80 lbs. phosphorus in all possible combinations, prior to flooding.
EFFECT OF NITROGEN ON PHOSPHORUS UPTAKE
As would be expected, the plants grown in the plots to which no phosphorus was added, did not show any significant variation in phosphorus composition at any level of nitrogen fertilization, or at any sampling date up to the 87th day. (Table 3.) The more important difference was the effect of nitrogen application on phosphorus uptake. The phosphorus content of plants rose from 0.17 to 0.23% in samples collected on the 42nd day, an increase of about 40%, as a result of the application of 40 lbs. nitrogen per acre. The rapid increase in vegetative growth that resulted from these treatments, probably caused a dilution effect and resulted in a decrease in phosphorus levels by the 68th day.
TABLE 3
% Phosphorus in Plant tissue as influenced by Treatment and Age.
Percent phosphorus in plant tissue
Treatment Days After Planting
42 68 87 No Po (). 136 0。丑34 0.37
N4o Po || 0 . 122 O. 20 0. III 9 Neo Po || 0.134 0.2 0.26
No Pao 0.172 0.46 (). I.47 N4o Peo || 0.231 0.32 0.30 Neo Pso 0.244 0.48 0.38
EFFECT OF PHOSPHORUS ON NITROGEN UPTAKE. (Table 4.)
The analytical data showed that the nitrogen content in the plant tissues increased with the addition of nitrogen
34

Page 85
fertilization as would be expected, but the more significant result is the effect of phosphorus on nitrogen uptake. The addition of phosphorus increased the nitrogen composition of plants at all levels of nitrogen fertilization. This resulted in accelerated growth and by the 68th and 87th day the nitrogen composition was depressed as a result of the dilution effect caused by vigorous vegetative growth.
TABLE 4.
% Nitrogen in Plant Tissue as influenced by Treatment
and Age.
% Nitrogen in plant tissue
Treatment Days After Planting
42 68 87
N, P, ... 8 . 37 I. O6 No Po 2.83 I. 72 ... 20 Nga P., 2.99 2.36 ... 20
No Pao 3.05 .2 ().94 No Pao 3. 60 25 0.88 No Pro 3.92 I. 84. I. O7
The most important result is the effect of phosphorus on nitrogen uptake during the early stages of growth. Table 5 presents the nitrogen taken up as a percentage of the total taken up by the plant over the entire season. The results are striking. The addition of phosphorus resulted in a most remarkable increase in nitrogen uptake during the first 42 days of growth. In the absence of phosphorus the uptake of nitrogen varied around 8%, with the addition of phosphorus this value rose to 20%. These values establish quite clearly the need for an readily available source of phosphorus at the commencement of the season.
SUMMARY
From the data presented, it would appear that rice benefits from basic dressings of phosphorus fertilization, not from the direct effect of supplying phosphorus to the plant
35

TABLE 5.
Nitrogen taken up by plants on the 42nd day expressed as % of the total Accumulated over the entire season
Treatment
% Total N. Accumulated
Treatment
% Total
N. Accumulated
N. P.
No Po
Ngo Po
8.7
9.39
6.3.
No Pao No Pao
Neo Pao
24.97
20.94
5. IO
Average
7. 96 Average 20.33
alone, but from the accelerated uptake of
nitrogen which
accompanies phosphorus availability.
LITTERATURE CITED
(l)
(2)
(3)
(4)
(5)
(6)
Mitsui S., Inorganic nutrition, fertilization and soil amelioration for lowland rice. Yokendo Ltd. Tokyo. 1955
Aiyer S. P., The effects of phosphate deficiency on rice. Proc. Indian Acad. Sci. 23: 165-193, 1946.
Ponnamperuma F. N., Review of the Symposium on the Mineral Nutrition of the Rice Plant. International Rice Research Institute. Manilla, Philippines
(1964).
Aoki M.,
82, 1941.
Journ. Sci. Soil and Manure, Japan, 15,
Seneviratne, S. T. Nitrogen uptake by the Rice Plant and a comparison of cultural practices with regard to their efficiency in meeting the nitrogen needs of the crop. Paper presented at the Annual Sessions of the Ceylon Association for the advancement of Science 1958.
Seneviratne, S. T. Potassium uptake by the Rice Plant. Paper presented at the Annual Sessions of the Ceylon Association for the Advancement of Science 1959.
36

Page 86
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Page 87
VEGETABLE GROWERS!
start with quality seed
Exotic and local varieties of vegetable seeds
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For particulars contact the
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P. O. Box 636
19, Saunders Place, COLOMBO 12

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Page 88
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Page 89
ALL CHI C4S ARE EGUAL
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ALL CHICKS ARE EQUAL
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Judging from external appearance it is impossible to distinguish one brand of chick from the other. But in actual fact no two brands are the same. Wherein does the difference lie
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Page 90
COCONUT
CO CON UT IS NOT A LAZY MAN’S CROP AS
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Printed by R. K. de Alwis at Lankapradipa Printing Works, l83, Trincomalie Street, Kandy and Published by the Editor, the National Agricultural Society of Ceylon, Department of Agriculture, University of Ceylon, Peradeniya, 5000

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Page 91

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