Effects Of Urea Type And Tosage On Agronomic Traits And Nitrogen Use Efficiency Of Rice

The aims of this study are(1)to screen nitrogen fertilizer varieties of higher nitrogen use efficiency(NUE)with comparison to conventional nitrogen application practice,and(2)to confirm the characteristics of yield growth and the feasibility of increase in profit by means of nitrogen reduction.Two relevant field experiments were carried out on rice in Haerbin region.The first experiment was called main effect-high NUE nitrogen fertilizer types screening,with 5 treatments,(1)CK,(2)traditional urea(CU),(3)Loss-controlled urea(LCU),(4)polymerenergized-netted urea(PENU),(5)humic acid coated urea(HCU),and the second experiment was called nitrogen rate reduction-ratio experiment with 8 treatments,(1)CK,(2)CU,(3)LCU,(4)LCU minus 10%(LCUR10%),(5)LCU minus 20%(LCUR20%),(6)LCU/CU=7:3,(7)LCU/CU=5:5,(8)LCU/CU=3:7.Both experiments were completely randomized block(CRB)design with four replications.The main conclusions are as follows:1.In the main effect experiment,all treatments increased in rice yield compared to CK,but only both LCU and PENU increased in rice yield compared to CU,with percentages of 16.2 % and 3.3% respectively.Yet the yield of HCU was inferior to CU;2.In the N rate reduction and ratio experiment,all treatments increased the yield significantly compared to CK,while LCUR10% and LCU/CU=3:7 increased yield compared to LCU with percentages of 27.31% and 11.96% respectively.LCUR20%,LCU/CU=7:3 and LCU/CU=5:5 were inferior to LCU in rice yield.3 For the yield components,grains per panicle was significantly and best correlated to the rice yield.In the main effect experiment,LCU and PENU increased the grains per panicle compared to CU,being 31.42% and 1.62 % higher respectively.While in N rate reduction and ratio experiment,grains per panicle of LCU related treatments were significantly higher than that of CU,the maximum of grains per panicle appeared for the LCU,being 76.91% higher than that of CU.4.Compared to CU,LCU increased significantly in RE(recovery efficiency),AE(agronomic efficiency)and PE(physiolological efficiency),being respectively 25%,53%? 53%(relative value);PENU increased either the nitrogen use efficiency but in a much lesser level compared to CU.