Effects of Nitrogen Application Rate and Planting Density on Grain Yields, Yield Components and Nitrogen Use Efficiencies of Rice

An experiment was carried out to study the interactive effect of nitrogen(N) fertilizer rate and planting density on rice yield and N use efficiency in order to provide a basis for rational cultivation management. The results indicated that the N rate and planting density had significant effects on grain yield of rice and the interactive effect was also significant. Compared with the no N treatment, the average yields of the treatments with N rates of 82.5, 165.0 and 247.5 kg/hm2 increased by 30.6%, 47.8% and 44.6%, respectively. The plant density was 21×104 seedlings/hm2 for the highest grain yield. Increasing the N rate and planting density significantly increased the number of spikes per unit. However, grains per spike, seed setting rate and thousand grain weight decreased with the increase of planting density. N use efficiency decreased at the higher N application rate, but increased first and then dropped with the increase of planting density. Planting density also had significant effects on grain yields of rice, increasing density promoted rice yield under the condition of low N rate(0 and 82.5 kg/hm2), but for the high density treatment, higher N rate significantly decreased the yield. In this study, the appropriate nitrogen application rate and plant density of rice were 194.9 kg/hm2 and 22.1×104 seedlings/hm2, respectively.