Effect of different N management practices on yield and its main formed factors in two laterseason rice genotypes

The present study employed sitespecific nitrogen management (SSNM), realtime nitrogen management (RTNM) and RTNM plus basic fertilizer (RTNMB) to discuss the effect of optimum N management practices above on yield and its main formed factors between Var. Ganwanxian 30 (GWX) and Var. Boyou 141(BY) in the intensive laterseason rice agriculture. Comparing to farmers N management practice, the sitespecific nitrogen management and realtime nitrogen management and RTNM plus basic fertilizer didnt affect yield significantly, aboveground biomass, N uptake by aboveground, harvest index (HI) and N harvest index (NHI) in either genotype rice. The yield was significantly correlated with aboveground biomass and N uptake by aboveground (P0.01). In all N application treatments, the average of yield, aboveground biomass and N uptake was 7.8 t/ha, 16.4 t/ha, and 175.6 kg/ha for GWX and 8.9 t/ha, 16.1 t/ha, N 150.6 kg/ha for BY. After N application, the average of yield, HI, NHI, spikelets per plant and grain per plant of BY was significantly higher than those of GWX (P0.05), while N uptake by aboveground, seed setting rate and 1000 grain weight of BY was significantly lower than those of GWX (P0.05). Comparing with farmers N management practices, the saved N percentage in RTNM was largest and that in SSNM was lowest, the basic N fertilizer application can maintain the stable of high yield. In a word, under the current intensive agriculture, the yield cannot decrease if the N amount decreased from farmers excessive N rate to the optimum rate, but the sustainability in the decline of N fertilizer rate need further explore in the future.