Abstract:

Aerobic rice is a new production system in which specially-developed varieties are grown under nonflooded, nonpuddled, and nonsaturated soil conditions. Insight is needed into water and fertilizer N response and water by N interaction to develop appropriate management recommendations. In 2003-2004, irrigation x N experiments were done near Beijing using variety HD297. Water treatments included four irrigation levels, and N treatments included different fertilizer N application rates and different number of N splits. The highest yields were 4.5 t ha-1 with 688 mm of total (rain plus irrigation) water input in 2003 and 6.0 t ha-1 with 705 mm of water input in 2004. Because of quite even distribution of rainfall in both years, the four irrigation treatments did not result in large differences of soil water conditions. There were few significant effects of irrigation on biomass accumulation, but yield increased with total amount of water applied. High yields coincided with high harvest index and high percentage of grain filling. The application of fertilizer N either reduced biomass and yield or kept it at the same level as 0 N and consistently reduced percentage grain filling and 1000-grain weight. There were no or inconsistent interactions between water and N. With the highest water application, five splits of N gave higher yield than three splits, whereas three splits gave higher yield than five splits with lower water applications. High yields with 0 N were probably caused by frequent overfertilization in the past, leading to high levels of indigenous soil N supply. A longer-term (over three years) experiment may be needed to quantify the N response of aerobic rice and how much N fertilizer can be saved in N-saturated soils.

Key words: Aerobic rice, Nitrogen use efficiency, North China, Water productivity