Optimizing yield, water requirements, and water productivity of aerobic rice for the North China Plain

Water resources for agriculture are rapidly declining in the North China Plain because of increasing industrial and domestic use and because of decreasing rainfall resulting from climate change. Water-efficient agricultural technologies need to be developed. Aerobic rice is a new crop production system in which rice is grown in nonflooded and nonsaturated aerobic soil, just like wheat and maize. Although an estimated 80,000 ha are cultivated with aerobic rice in the plain, there is little knowledge on obtainable yields and water requirements to assist farmers in improving their management. We present results from field experiments with aerobic rice variety HD297 near Beijing, from 2002 to 2004. The crop growth simulation model ORYZA2000 was used to extrapolate the experimental results to different weather conditions, irrigation management, and soil types. We quantified yields, water inputs, water use, and water productivities. On typical freely draining soils of the North China Plain, aerobic rice yields can reach 6-6.8 t ha(-1), with a total water input ranging between 589 and 797 (rainfall = 477 m and water application = 112-320 mm). For efficient water use, the irrigation water can be supplied in 2-4 applications and should aim at keeping the soil water tension in the rootzone below 100-200 kPa. Under those conditions, the amount of water use by evapotranspiration was 458-483 mm. The water productivity with respect to total water input (irrigation plus rainfall) was 0.89-1.05 g grain kg(-1) water, and with respect to evapotranspiration, 1.28-1.42 g grain kg(-1) water. Drought around flowering should be avoided to minimize the risk of spikelet sterility and low grain yields. The simulations suggest that, theoretically, yields can go up to 7.5 t ha(-1) and beyond. Further research is needed to determine whether the panicle (sink) size is large enough to support such yields and/or whether improved management is needed.