Effects of planting density and nitrogen application rate on absorption and utilization of nitrogen in rice

The effects of planting density and nitrogen application rate on nitrogen absorption and utilization by rice were studied with Wuxiangjing 9(Japonica variety).Results showed that increasing nitrogen application rate increased total N uptake,but decreased the percentage of nitrogen exported(PNE)from vegetative organs,nitrogen harvest index(NHI)and nitrogen efficiency for grain production(NEGP).On the contrary,increasing planting density could increase not only total N uptake but also PNE,NHI and fertilizer utilization efficiency(FUE).Thus,it is an effective way to increase nitrogen utilization efficiency by decreasing nitrogen application rate and transplanting more plant within proper range.The results indicated that there was basically stable requirement for nitrogen and FUE during rice growing period under high grain yield(about 9 t·hm -2).The nitrogen requirement for producing 100 kg grain was 2.1 kg,and the FUE was 42% in this experiment.