スリランカ

Double cropping of paddy fields has become possible under rainfed condition with the introduction of improved varieties of rice with shorter term of growth and higher yields (HYVs) that were introduced in the 1960s, and has progressively grown since then in Sri Lanka. The double cropping coupled with the labour intensive paddy production technology affected not only on the previous system of low-land utilization but also buffalo keeping and upland farming which were closely integrated with low-land farming during the single cropping. The dissemination of double cropping has compeled farmers to concentrate more on the improvement and maintenance of soil fertility, that might be exhausted through continuous cropping. The purpose of this study is to examine and ascertain the development trend towards the double cropping of paddy fields with the changes of production technology and management strategies, from the aspect of improving soil fertility. For this purpose, a traditional village, Moragalla, was selected. Findings are summarized as follows: 1. The double cropping has been spread without any improvement of the field tracts. In addition to storing water for paddy fields, the higher and larger levees provided multipurposive benefits, such as grass cutting for buffaloes, growing some subsidiary crops on the top of levees, drying and temporarily storing reaped paddy produce. The usage of the levees in this way has coincided with single cropping of paddy fields, but has disintegrated mainly due to the changes of forming practices and the labour scarcity under the double cropping system since the 1960s. The labour required for the maintenance of levees even has sometimes been cut. As a result, levee-breakes have tended to increase and accelerate soil erosion of the field. The reduction of the grass cut on the levees has also made it inconvenient for peasants to keep buffaloes. 2. The sharp reduction of buffalo numbers in the 1970s was due to insufficient pasturing. The reasons for this were: (1) the lack of fallowed paddy fields which were fallowed in the yala season but were now raised to rice under the double cropping system in the paddy fields, (2) coconut lands on which the buffaloes previously pastured became scarce due to the introduction of intertilled crops such as banana, and (3) the decrease of waste lands, much of which had been reclaimed to coconut. The decrease in the number of buffaloes has resulted in poor manuring of paddy fields. 3. The lack of land improvement adversely affected not only on achieving higher yields of HYVs, but also the raising of other subsidiary crops on the paddy fields to improve the soil conditions through crop rotation. 4. Because of the yield sharing tenancy system and the traditional customs involved therein the adoption of advanced production technology is somewhat retarded. It goes without saying that there is less incentive for improving soil conditions under this system. 5. The iron (mold-board) plough replaced the indigenous wooden plough in the later part of the 1960s. They were well suited for cultivating HYVs in the sense of ploughing speed and ploughing weeds under furrow slices. However, negatively, there have been some demerits. The ploughing with iron plough requires a larger quantity of water to cover the larger furrow slices and larger size of buffalo teams for trampling operations. The partial introduction of tractor ploughing since the 1960s is also not more than a substitute for buffalo driven ploughing. 6. The development of farming practices has been centered on broadcast sowing on muddy soil with the application of chemical fertilizer both for basal and top dressings and chemical weedicides. This has tended to degenerate and ignore the traditional dry farming. It is the time to reevaluate the traditional dry farming, which has many merits, ie. : minimizing water requirements and labour input, and lowering farmers’ expenditure on chemical fertilizers and weedicides.