RICE WHEAT IN SOUTH-ASIA - SYSTEMS AND LONG-TERM PRIORITIES ESTABLISHED THROUGH DIAGNOSTIC RESEARCH

Rice and wheat are grown in rotation on about 12 million hectares in South Asia. Yields in this rotation have increased over time, but evidence indicates that factor productivity may be declining. Recently, multidisciplinary teams of agricultural scientists conducted diagnostic surveys in several rice-wheat areas in South Asia. This paper reviews rice-wheat system problems and longer-term issues of sustainability identified through the surveys (near-term problems affecting rice and wheat yields are discussed less fully). System problems include poor wheat populations caused by the poor soil structure and plow pan formed for puddled rice, late wheat planting resulting from late rice harvesting, and losses to grassy weeds encouraged by continuous rice-wheat cultivation. Sustainability issues include soil nutrient depletion and possible buildup of insects, weeds, and diseases.