Effects Of Slow/controlled Release Urea On Crop Yield,nitrogen Use Efficiency And Greenhouse Gas Emissions

China is the most populous developing country in the world,as the area of farmland per capita was quite limited.In order to protect the food safety,it can only be achieved by increasing yields.Nitrogen application is an effective way to improve crop yield.However,traditional synthetic nitrogen fertilizer has a high nutrient release rate,and it needs to be applied many times to meet crop growth demand.After the application of synthetic nitrogen fertilizer,about 40%-50% nitrogen is lost by leaching,runoff,volatilization,nitrification and denitrification,and lead to low nitrogen utilization efficiency and serious pollution to the environment.The slow/controlled of urea as a new fertilizer can slow down or control the rate of nutrient release or the rate of nutrient conversion in the soil to achieve nutrient supply and crop demand synchronization,so as to improve fertilizer utilization and reduce environmental pollution.However,the effect of continuous application of slow/controlled release urea on crop productivity and the environment is unclear.Therefore,it is necessary to carry out the study of the effect of new slow/controlled release urea and the evaluation of environmental benefits.The effects of different controlled release urea on crop growth,yield,nitrogen use efficiency and ammonia volatilization in rice-rape rotation system were studied in field experiment in Jingzhou City,Hubei Province in 2013-2015.The effects of different slow/controlled release urea on the yield,nitrogen use efficiency,ammonia volatilization and greenhouse gas emission in the double cropping rice system were studied,and the responses of greenhouse gases to different rice varieties and irrigation methods were studied.The main results are as follows:(1)The application of controlled release urea can significantly improve the yield of rice and oilseed rape compared to common urea,controlled release urea and controlled release urea + urea can reduce the dosage of 21.4% and achieve stable rice production,and enhance grain yield 5.4%-9.9% under the same amount of nitrogen fertilizer.Meanwhile,recovery and agronomic efficiency of N fertilizer were improved.(2)Environmentally Smart Nitrogen(CRU1)and biodegradable ester-coated urea(CRU2)treatments can significantly improve the yield of oilseed rape,and the sustainability and stability were better,enhance grain yield 8.3%-26.8% under the same amount of nitrogen fertilizer.Meanwhile,recovery and agronomic efficiency of N fertilizer were improved.(3)Ammonia volatilization loss is an important nitrogen loss path in rice and oilseed rape fields.The seasonal loss of ammonia fertilizer in rice and oilseed rape season is 4.4%-15.9% and 0.6%-3.5% of total nitrogen fertilizer application.Controlled release of urea can significantly reduce ammonia volatilization in rice-oilseed rape rotation system.Compared with common urea,controlled release urea can reduce the cumulative loss rate of ammonia volatiles 58.5%-78.6% in rice-oilseed rape rotation system.(4)Considering the factors such as crop yield,nitrogen use efficiency and ammonia volatilization in rice-rape rotation system,the CRU1 treatment was the best in rice season,and the CRU1 and CRU2 treatments were the best in oilseed rape season.(5)The application of slow/controlled release urea and EM bacteria can significantly improve the yield of early rice(14.9%-15.8%),late rice(16.1%-20.7%)and total annual(15.4%-18.0%)compared with common urea.(6)The application of slow/controlled release urea could effectively reduce CH4(22.9%-37.5%)and N2O(6.3%-41.8%)emission compared with common urea in paddy field.Meanwhile,N2 O cumulative emissions decreased by 20.0%-46.1% and 36.1%-45.3%,respectively,and the cumulative N2 O accumulation in early and late rice treatments decreased by 26.1% and 30.4%,respectively.(7)The application of slow/controlled release urea could significantly reduce the GWP and GHGI.The polymer-coated controlled-release urea(CRU)or nitrapyrin-treated urea(CP)treatment is the best option in early and late rice season,respectively.They are able to enhance the yield of rice and reduce the greenhouse gas emission at the same time.(8)The yield potential of different rice varieties was different.The highest yield and lowest total accumulated emission of N2 O and GWP in Liangyou 42 during early rice season.The lowest total accumulated e mission of CH4 in Liangyou 287 during early rice season.The total accumulated emissions of CH4 and N2 O and the lowest GWP in Jingchuyou 148 during late season.Liangyou 42 and Xiangfengyou 9 have the lowest GHGI during early and late rice season,respectively,which can enhance the rice yield and reduce the greenhouse gas emission intensity.(9)In the present study,the yield of rice between the two irrigation methods was similar.Compared with conventional irrigation(W1),the accumulated CH4 emission in FFP and CP treatment decreased under deep-water irrigation(W2),and the cumulative emission of CH4 increased in EM treatment.W2 can reduce the accumulated N2 O emission in early rice and late rice paddy.The GHGI was the lowest in CP treatment during the early rice season with W2 condition,and the CP treatment during the late rice season with W1 condition.In addition,the continuous application of slow/controlled release urea can achieve high yield of double cropping rice and rice-oilseed rape rotation system,and can significantly reduce soil ammonia volatilization and greenhouse gas emissions,which can be widely used as management mode for high yield and low carbon production of the local agricultural production.