Production trends of legumes in rice-based cropping system of Sri Lanka

摘要

Rice (Oryza sativa) followed by rice is the major cropping system traditionally practiced in Sri Lanka, often on imperfectly- to poorly-clrained soils. However, since the early 1930s, expansion of irrigated area resulted in inclusion of welldrained soils in this production system. Expansion of irrigated area, however, resulted in changed hydrology, leading to insufficient year-round water availability to reliably practice a rice-rice cropping system. In the Maha season (major rainy season from mid-Oct to mid-Jan) all lands in command areas of almost all irrigation schemes have enough water for the rice crop. But in the Yala season (minor rainy season from late Apr to Aug) only a portion of the command area can be cultivated with rice due to inadequate availability of water. Due to the low water requirement of legumes and other upland crops compared to rice, these have been introduced into the rice-rice cropping systems since the early 1960s. Comparatively higher returns from legumes and other field crops made the cropping system of Maha season rice followed by other field crops in the Yala season more popular.