Grain Yield Construction And N Fertilizer Efficiency Of Hybrid Rice Under Different N Applications

To clarify the effects of different nitrogen application treatments on grain yield construction of hybrid rice and utilization efficiency of nitrogen fertilizer, the nitrogen fertilizing experiment were conducted with Liangyou Peijiu and San You 63 in 2002, the pioneer hybrid rice combination ,as the material at Changsha, Hunan.The main results are as follows :1. The applied amount of nitrogen had a significant effect on grain yield.The Liangyou Peijiu experiment results showed that during 0-240kg/hm2(pure nitrogen),the relation of N amount to grain yield was expressed in a single peak curve with the peak(10.7t/hm2) of grain yield at 180kg/hm2 of N and with the most apparent yield-increasing effect between 120 and 180kg/hm2 of N.The Sanyou 63 experiment results showed that during 0-225kg/hm2(pure nitrogen) ,The relation of N amount to grain yield was expressed in a single peak curve with the peak (7.84t/hm2) of grain yield at 120kg/hm2 of N and with the most apparent yield-increasing effect between 60 and 120kg/hm2 of N.2. Hybrid rice had a special requirement to the source organ at heading stage and applying N had an obvious effect on the accumulation of dry matter in late stage. A higher N amount would ensure a higher LAI of hybrid rice and maintain a higher rate of leaf dry matter and blade weight per shoot at heading stage ,which is favorable to increasing the photosynthetic capability of plants and keeping from early senescence and promoting the complete transfer of photosynthetic in late stage to fully make use of the great yield potentiality in hybrid rice.3. There existed a great variation in the agronomic efficiency (AE) of N fertilizer among various N treatment and different special The highest AE (16.10) occurred at the Namount of 180kg/hm2 and lowest (7.43) at 240kg/hm2 in the Liangyou Peijiu experiment with increasing of applied amount of nitrogen ,the agronomic efficiency of N fertilizer decreasing .The highest AE(25.50) Occurred at the amount of 60kg/hm2 and lowest (2.33) at 240kg/hm2.