Effects Of Optimized Fertilization On Nitrogen Use Efficiency And Environmental Effects Of Rice Under Different Rotation Systems

Rice is one of the most important food crops in our country.In recent years,with the increasing population,the demand for food has been increasing.Especially,the current cultivated land area decreasing year by year,improving the yield of grain crops which plays an important role in China’s food security.However,most of the farmers in China at present only blindly pursue crop yield,and excessive application of chemical fertilizers,which making the use of nitrogen fertilizer efficiency decreased.Moreover,it makes a variety of environmental problems.The establishment of soil-plant-enviroment optimization,synchronous crop yield and fertilizer efficiency has become one of the important measures for sustainable development of agriculture.This experiment conducted from 2014 to 2016 in a long-term experiments site in the Agriculture Science Research Institute of Rugao of Jiangsu.The control(CK)and the farmer’s fertilizer practices regime(FFP)and the optimal fertilization regime(OPT)were established in three cropping systems,including the rice-wheat rotation system(RW),the rice-vegetable rotation system(RV)and the rice-fallow cropping system(RF).This study aimed to investigate the effects of different fertilization methods on rice yield and nutrient uptake and utilization under the three rice rotation systems in the middle and lower reaches of the Yangtze River,which would provide the theoretical basis for the production.The main findings are as follows:1.In the optimal fertilization regime,a high yield was still maintained with reduce N supply amount.Compare with the optimal fertilization regime,the farmer’s fertilizer practices regime decreased by 1.4%in average yield from 2015 to 2016.The increased yield of the optimal fertilization regime was attributed to the increased spikes numbers,grains per spike and 1000 grain weight.Under the same fertilization systems,the yield of the rice-vegetable rotation system was significantly higher than that of the others rotation systems,because of the fertilizer application of fore crop in the rice-vegetable rotation system is higher than others rotation systems in 2016.2.Nitrogen optimal management significantly improved nitrogen utilization efficiency in rice.Compared with the farmer’s fertilizer practices regime,the nitrogen agronomic efficiency,nitrogen recovery efficiency and nitrogen partial factor productivity were increased by 70.3%,69.4%and 68.0%respectively under the different rotation systems.In the way of the farmer’s fertilizer practices regime,due to the nitrogen fertilizer application excessived,a large number of fertilizer are wastful.Moreover,it also makes nitrogen fertilizer utilization decreased.The model of nutrient optimize management could be rational allocation N accumulation and distribution of rice plant,collaboration to achieve the high grain yield and increase fertilizer use efficiency.3.The optimal fertilization regime can reduce the NH3 volatilization and N2O emission flux in paddy field.Compared with the farmer’s fertilizer practices regime,the optimal fertilization regime could significantly reduce the total amount of NH3 volatilization and the ratio of nitrogen fertilizer application,the average decline was 49.1%and 4.0%respectively.NH3 volatilization and N2O emission flux are affected by the amount of fertilizer application.Based on the above results,it can be seen that the optimal fertilization regime can reduce NH3 volatilization and N2O emission flux.Meantime,it can reduce nitrogen loss and improve nitrogen use efficiency,while also stabilizing or even increasing rice yields.In summary,the three different rotation systems could be rational allocation N accumulation and distribution of rice plant by the optimal fertilization regime.optimizing the application rate of fertilization and the proportion of the operation,Moreover,it is consistent with the crop demand for nitrogen.It also could be collaboration to achieve the high grain yield and its composition,increase fertilizer use efficiency.Optimize the yield composition of rice,and finally achieve the purpose of increasing yield,for different rotation system under the high and stable yield of rice to provide a theoretical basis.