Effect of Nitrogen Fertilizer Regimes and Returning Straw on N Availability and Forming Yield of Direct-sowing Rice

A field study was conducted to determine the effect of nitrogen regimes and returning straw into paddy on the yield and nitrogen utilization of rice in the process of mechanical precise-quantity hill-drop drilling application.Based on the same amount of nitrogen fertilizer,rice growth dynamics,light usage,nitrogen accumulation and yield components were examined when the fertilizer was applied by different ratios among the base fertilizers,tiller fertilizer and panicle fertilizer,and whether rape straw returning was applied as base fertilizer.The results showed that increasing the percentage of ear fertilizer ratio could decrease ineffective tiller number,but increase chlorophyll content in function leaves,LAI,and photosynthetic rate.The photosynthetic rate at filling-grain stage and 1 000-grain weight increased when the straw was returned into paddy as based fertilizer.Both increasing the application percentage of ear fertilizer and replacing the nitrogen fertilizer partially with rape straw as based fertilizer could increase the photosynthetic efficiency and nitrogen utilization rate of direct-sowing rice,and could lead to higher yield.