Crop management research and recommendations for rainfed lowland rice production in Cambodia

摘要

Rainfed lowland rice dominates the farm cropping systems in Cambodia. More than 80 percent of the cultivated area sown to rice is rainfed lowland culture: the systems are traditional and ancient in origin and rice is monocropped year after year on thesame land; shortages of water and inadequate irrigation infrastructure are typical of rural areas. In areas where supplementary water is available, other crops are also grown, providing a measure of diversification, crop rotation, change of diet and opportunities for off-farm sales and trading-all positive factors. Supplementary water also enables rice production to be intensified with two-or even three-crops grown annually. Where supplementary water is insufficient for a second rice crop, growers willtypically sow a second short-duration cash or food crop. Mung beans, black gram and vegetables are popular, and frequently precede or follow a wet season rice crop. Rainfed lowland rice is grown in a variety of environments, even where production resources are poor: it is not uncommon, for example, for no fertilizer to be used despite the low level of nutrients, particularly N and P (White, Oberthur and Sovuthy, 1997). The risks inherent in intensification can be minimized with the choice of suitable varieties. For example, earlymaturing varieties that flower to coincide with the peak of the rain season risk damage to spikelets and this reduces pollination levels; furthermore, spikelets at this time are more likely to be damaged by rodents. An understanding of crop scheduling is essential for double or multiple cropping, in order that growers can select varieties, stagger planting to suit the season and space crops on their small areas of land (Sarom, 2001).