Nitrogen Utilization And Loss In Winter Wheat-Summer Maize Rotation System Of Beijing Suburb

Due to the serious loss of nitrogen (N) in suburb of Beijing, the study focused on the N loss in winter wheat (Triticum aestivum L.)-summer maize (Zea mays L.) system. In order to trace the loss of nitrogen (N),15N labelled fertilizer was applied at the pot experiment in greenhouse from2012to2013. The whole experiments were conducted in of Beijing Academy of Agriculture and Forestry Sciences and agricultural nonpoint source pollution research center of Beijing Fangshan District Academy of Agricultural Science. The ammonia volatilization, N2O emissions and leaching losses of winter wheat-summer maizesystem were investigated through in-situ soil column experiment. The main results were as followed:1. Nine nitrogen fertilization treatments (N at22-266mg/kg) were maintained in the pot experiment, and the biomass of maize were5600～100300mg/kg. According to the15N tracing results, the plant N accumulation were11.83%～67.60%, the soil N accumulation were21.01%～39.32%, and the N loss rates were11.39%～48.85%. In N at88mg/kg treatment, the plant N accumulation was67.60%, the soil N accumulation was21.01%, and the N loss rate was11.39%. Compared with N at22、44、66mg/kg treatments, in N4treatment, the plant N accumulation increased55.8%,19.4%, and28.1%. In the meantime, the soil N accumulation reduced18.3%,11.7%, and12.7%. Moreover, the N loss rate reduced37.4%,7.7%, and15.4%. Compared with N111.133、177、222、266mg/kg treatments, in N88mg/kg treatment, the plant N accumulation increased9.2%,12.7%,19.5%,26.6%, and28.0%. In the other hand, the soil N accumulation reduced7.5%,4.2%,14.9%,17.8%, and5.1%, and the N loss rate during the maize growing period was reduced13.8%,28.9%,37.9%,37.2%,27.2%,19.4%, and16.1%. The shortage and excess supplied of the N fertilizer seriously affects crop yield and N efficiency. In that case, the N88mg/kg treatment was the most reasonable N fertilization than the other treatments.2. The ammonia volatilization was mainly occurred at the13th after nitrogen fertilizer applied in the winter wheat-summer maize system. The different nitrogen levels treatments had relatively different amount of ammonia volatilization, with which the increased of N caused the increased of ammonia volatilization. In the winter wheat period, the amount of ammonia volatilization were3.01～21.20kg/hm2with different N treatments. And the amount of ammonia volatilization was higher than the previous winter period reviving basal dressing period. In summer corn period, the amount of ammonia volatilization were4.75-37.12 kg/hm with different N treatments. And the amount of ammonia volatilization was higher at topdressing nitrogen than base. The total amount of ammonia volatilization with the treatment of N150kg/hm2were9.46kg/hm2(in wheat period) and15.21kg/hm2(in corn period). Quadratic curve drawn through the simulation showed that, when the amount of farmland soil nitrogen fertilizer when N150kg/hm2had the minimum rate of volatilization losses and the highest crop yields in the winter wheat-summer maize system. When the quantity of nitrogen was more than N150kg/hm2, the nitrogen loss through ammonia volatilization could not be ignored.3. Winter wheat area in the suburbs of Beijing-summer maize rotation system in farmland has soil nitrification N2O fluxes showed significantly seasonal and diurnal variation. In the winter wheat period, the N2O emissions were0.32-2.21kg/hm2, the N loss rates were0.37%-0.49%, and0.51%. In the summer maize period, the N2O emissions were1.09～15.65kg/hm2, the N loss rates were2.52%-3.64%. Due to the summer season the average temperature is higher than winter wheat corn season, the soil N2O flux was higher in maize period than in wheat period.4. The increased application of nitrogen fertilizer significantly increased the soil NO3--N content and N leaching loss in the treatment winter wheat-summer maize system. Through determination of the eluent, in the wheat period, the N losses were1.74-4.10kg/hm2with the various levels of N treatments. Otherwise, in the corn period, the N losses were0.66～9.76kg/hm2with N0-N7treatments.5. The increased application of nitrogen fertilizer significantly increased the crop yield. However, the amount of N fertilization above150kg/hm2had negative effect on the treatment crops yields. In this study, the treatments amounts of nitrogen were at0-400kg/hm2, the wheat yields were at5045.78-6346.20kg/hm2, and the corn yields were at7311.6～10389.60kg/hm. The highest yields of the treatment crops were obtained in N150kg/hm2treatment, which were6346.20kg/hm2of wheat and10389.60kg/hm2of corn.In conclusions, as for the winter wheat-summer maize rotation system in Beijing, the reasonable amount of nitrogen fertilizer application could improve the plant N input, N use efficiency, and crop yield. In the meantime, it also could reduce the loss of nitrogen and environment problems.150kg/hm nitrogen fertilization was the most reasonable amount of nitrogen application for the winter wheat-summer maize rotation system in Beijing. The effective application of nitrogen fertilization could improve the coordinately development of sustainable agriculture-economic and environmental benefits.