WATER AND NUTRIENT USE EFFICIENCY OF HIGHLY PRODUCTIVE RICE CROPPING SYSTEMS

摘要

Rice production in Asia needs to increase to feed an ever-growing population. More than 75% of the rice produced comes from irrigated land. The water crisis is threatening the sustainability of the irrigated system. Rice is especially sensitive to declining water availability since it requires much water and has a low water-use efficiency. Therefore, water-saving production technologies need to be developed. To increase both grain yield per unit water input as well as yield per unit area, factor productivity of other inputs such as nitrogen need to increase as well. Cutting back on the relatively large and unproductive losses of seepage and percolation can reduce water input in rice production. Water-saving irrigation such as saturated soil cultureand alternate wetting and drying can drastically reduce these losses. Under these technologies, yields also decline, though to a lesser extent, and water productivity increase. A new concept of growing rice using less water is aerobic rice: high-yieldingrice grown in non-puddled, aerobic soil under high inputs of water and nutrients. New, aerobic, rice varieties are needed if this system is going to be successful in the tropics. The major cause of low nitrogen use efficiency is that the supply of nutrients is not well synchronized with the demands of the crops. Crop simulation studies and field experiments contributed to a better understanding of nitrogen demand of irrigated rice crops during consecutive development stages. Smart farming technologies,like site specific management, aiming at both productivity and efficiency gains are promising. Crop and soil diagnostics will be needed to increase the accuracy of nitrogen recommendations in water saving rice-cropping systems. The combination of fielddiagnostics and modeling would enable a greater use of dynamic optimization strategies in the field.