Study On Annualnitrogen Cyclingandbalanceofcornandwheat Double Cropping Fieldbased On Strawincorporatedinthe Northern Henanprovince

With the application of total straw return,serious problems has been caused by excessive applying of nitrogen fertilizer,such as loss of fertilizer,low resource utilization,and environmental pollution.In this study,afield experimentwas carried out to deal with these problems.In the corn and wheat double cropping system,nitrogen application amountwas433.80kg·hm^-2in maize season,0,160,220 and280kg·hm^-2in wheat season.The effects of nitrogen utilization efficiency and yield of winter wheat under different nitrogen rate with straw incorporated hadbeen analyzed.Nitrogen cycling and balance of cornandwheatdoublecroppingfieldhadbeen evaluated.The results showed that:1.The population and dry matter accumulation of winter wheat under nitrogen treatments were significantly higher than no nitrogen treatments inthe wintering,green and jointing period.During anthesis and mature period,the population and dry matter accumulation of winter wheat were significantly increased with the adding of nitrogen application level and reached the highest under the nitrogen application amount 220kg·hm^-2.The population and dry matter accumulation of winter wheat were decreasedwith the continuousadding of nitrogen application level.Therefore,the tillering ability and dry matter accumulation of wheat plantcould be improved significantly with proper nitrogen fertilizer application.2.The N content of winter wheat plants showed a single peak curve during the whole growth period and reacheda peak at greenperiod.The N content and N accumulation of winter wheat plants were significantly increased with the adding of nitrogen application level and showed the highest under the nitrogen application amount 280kg·hm^-2.Thenitrogen utilization efficiency and nitrogen partial factor productivity significantly decreased with the adding of nitrogen application level.There was no significant difference in the nitrogen agronomic efficiency,nitrogen recovery efficiency and nitrogen harvest index under different treatments.The ear number,grain number per spike,fertile spikelet and yield could be improved significantly with nitrogen fertilizer application.The grain yields under the treatment of 280 and 220kg·hm^-2was higher and increased 24.44%,19.38% compared withno nitrogen treatments.3.N content,N accumulation,NO3--N content,NO3--N accumulation of soil in winter wheat seasonincreased with nitrogen fertilization rate.N content,N accumulation,NO3--N content and NO3--N accumulation of soil in winter wheat season showed the highest under the nitrogen application amount 280kg·hm^-2.Soil NO3--N was mainly accumulated in topsoil at corn mature stage and wheat mature stage.4.TheNH3 volatilization accumulation of base fertilizer and first topdressing significantly decreased because of rainfall before fertilization in maize season.The NH3 volatilization accumulation of second topdressingwas 4.32 times of base fertilizer and 1.37 times of first topdressing in maize season.The NH3 volatilization accumulation oftopdressing at jointing stage significantly decreased compared tobase fertilizer because of irrigation before fertilization in wheat season.The accumulation of NH3 volatilization at jointing stage under the treatment of 160,220 and 280kg·hm^-2N was 1.59,3.14 and 6.16 timesof no nitrogen treatments,respectively.The NH3 volatilization rate and accumulation of maize season were significantly higher than wheat season.5.N surplus amount was-58.35kg·hm^-2 under the treatment of 433.8kg·hm^-2inannualwhich was a depletion of soil nitrogen.The N surplus amount was 35.01kg·hm^-2 under the treatment of 593.8kg·hm^-2inannualwhich had alower yield and a risk of soil nitrogen consumption.The N surplus amount was 63.39kg·hm^-2 under the treatment of 653.8kg·hm^-2inannualwhich showed balance of nitrogen input and nitrogen output.The N surplus amount was 69.25kg·hm^-2 under the treatment of 713.8kg·hm^-2inannualwhich had a high input and high loss of nitrogen,and polluted the environmentat the same time.According to the results above,the recommended annualnitrogen application rate was 653.8kg·hm^-2under the condition of straw returning.In this amount of nitrogen application ratecan effectively control the loss of nitrogen leachingand ammonia volatilization.At the same time in this amount of nitrogen application rate can save production cost and maintain the sustainable development of nitrogen in farmland system.