Abstract:Using the split-plot design, effects of nitrogen application amount, planting density and their interaction on yield of super early rice (Oxyza sativa L. cv. Zhongzao 22) were studied. The results show that the yield is significantly impacted by nitrogen application amount, planting density and their interaction. Under the middle or low nitrogen application amounts, planting density does not have obvious impact on yield, while under the higher nitrogen application amount, appropriate decrease of planting density can improve the yield. For the main effects of nitrogen, effective panicles, biomass, yield, total nitrogen accumulation, maximum number of tiller, tiller panicle rate (rate of tiller productive panicles account to total effective panicles) and nitrogen requirement for 100 kg grain production are increased when nitrogen application amounts are increased, however an opposite trend is discovered for seeding setting rate under N application rates 0～195 kg/ha. Spikelets per panicle of the nitrogen application treatments are significantly higher than that of the non-nitrogen treatment. Effective panicles and biomass are increased, while spikelets per panicle and tiller panicle rate are reduced significantly as planting densities from 24×104 to 30×104 hill/ha. The seeding setting rate, apparent utilization ratio of nitrogen and total nitrogen accumulation are not apparently influenced by planting density. Biomass and total nitrogen accumulation have parabolic relationships with yield. The optimum biomass and total nitrogen accumulation are 14.90 t/ha and 155.4 kg/ha respectively. Under the experimental condition, the combination of N 195 kg/ha and 30×104 hill/ha is favorable for high yield of Zhongzao 22.