Effect Of Urea And Slow Release Nitrogen Fertilizer On Rice And Wheat Yield And Nitrogen Fertilizer Efficiency

China is the biggest producer and consumer of nitrogen fertilizer in the world.The application of nitrogen fertilizer plays an important role in promoting China’s food security.However,only a small amount of nitrogen applied in large rate can be used by the crops and remain in the soil.According to relevant reports,the nitrogen recovery of applied nitrogen fertilizer is 35%in China,only 70%of the world’s average level.Low utilization rate of nitrogen fertilizer not only leads to higher cost of fertilizer application but also causes environmental concerns,especially eutrophication of water and the increase of greenhouse gas emissions.Therefore,investigation on enhancing the utilization rate of nitrogen fertilizer and reducing the fertilization costs is very important in crop production and eco-environment protection.As a new type of fertilizer,slow-release nitrogen fertilizer can satisfy the dynamic demand of nitrogen during crop growing season through controlled-release mechanisms,and thus improve the utilization rate of nitrogen fertilizer and reduce application times.In this study,the effects of one-time application of ordinary urea and slow-release nitrogen fertilizer on the physiological characteristics,yield and nitrogen utilization of wheat and rice were investigated through field and pot experiments,so as to provide theoretical and technical support for more efficient fertilization and simplified crop production.The main results obtained are as follows:(1)The nutrient release curve of resin coated urea was s-shaped,in which 0～5 d was the slow release period of nutrients,5～84 d was the rapid release period of nutrients,the release curve was basically linear,and 84～112 d was the attenuation period of nutrients.Under the culture condition,the fastest time of nutrient release rate was 47th day.(2)In this experiment,the optimal ratio of urea and slow-release nitrogen fertilizer for wheat was 7/3.The experimental study in 2017 showed that under the conventional nitrogen application level,the wheat yield,nitrogen accumulation,grain and straw nitrogen absorption under the treatment of urea and slow-release nitrogen fertilizer with the proportion of 5/5 were all better than those under the conventional nitrogen application,which increased by 9.02%,8.40%,16.18%,5.41%and 7.94%,respectively,The experimental study in 2018 showed that under the conventional nitrogen application level,the wheat yield,nitrogen accumulation,grain nitrogen absorption with the ratio of urea to slow-release nitrogen fertilizer 7/3 was better than that with the ratio of urea to slow-release nitrogen fertilizer 5/5,which increased by 8.82%,17.81%,14.03%,4.76%,respectively,Under the condition of nitrogen reduction by 20%,the yield,apparent nitrogen use efficiency,nitrogen accumulation,grain and plant nitrogen absorption of wheat treated with urea and slow-release nitrogen were reduced to a certain extent,but not to a significant degree,when compared with the conventional nitrogen 10/0 treatment.(3)In this experiment,the optimal ratio of urea and slow-release nitrogen fertilizer for rice was 5/5.At the conventional nitrogen application level,the rice yield,nitrogen apparent utilization rate,nitrogen accumulation,nitrogen uptake in grain and straw in urea and slow-release nitrogen fertilizer treatments were all higher than that in conventional nitrogen application treatments(7/3,5/5,3/7,0/10).During the two-year experiment,the yield and nitrogen accumulation of rice treated with urea and slow-release nitrogen fertilizer with the proportion of 5/5 increased by 107.84%,156.15%,95.18%and 68.41%,respectively,compared with that treated with conventional nitrogen treatment 10/0.The apparent nitrogen use efficiency of rice treated with 70%slow-release nitrogen fertilizer was 299.4%and 96.10%higher than that treated with conventional nitrogen fertilizer.Under the condition of nitrogen reduction by 20%,the rice yield,nitrogen accumulation amount,nitrogen apparent utilization rate,nitrogen absorption amount of grain and straw in urea and slow-release nitrogen fertilizer combined treatments(7/3,5/5,3/7,0/10)were improved to a certain extent compared with the conventional nitrogen 10/0 treatment.