Effects of N and Water Coupling on Early-Rice Yield and N Use Efficiency in Red Soil Regions

In a field experiment,effects of variation of the use of water and N fertilizer on early-rice yield,yield composition and N use efficiency in red soil regions were studied.Results showed that in comparison with flooding irrigation,intermittent irrigation increased the number of valid panicles per unit area,1000-grain weight and yield of rice,and total N uptake by 1.7% ~ 6.2%,but decreased apparent N recovery rate;with the rise of nitrogen application rate,1000-grain wt and seed setting rate decreased,but the number of valid panicles per unit area,yield,total N uptake, and nitrogen use efficiency increased;the effects of N application pattern on yield composition of early-rice varied with irrigation method and N application rate,showed a different changing rule,moreover,split application significantly increased yield,total N uptake and apparent N recovery efficiency,but did not show much difference three and four times of split application.From the experiment it can be concluded that the yield and the nitrogen uptake of the crop was the most reasonable when intermittent irrigation,and application of 210 kg/hm~2 pure nitrogen split into 50% as basal, 30% at tillering and 20% at panicle forming as sidedressing were adopted.Comparing with the conventional farming practice of the local farmers,this treatment could increase yield by 11.1%,and N uptake by 34.3%,and raise apparent N use efficiency up to 36.7%.It is an ideal treatment taking account of production,ecological,and economical benefits.