Nitrogen Loss And Related Environmental Effects In Agricultural Ecosystem In The North China Plain

On the base of examines of crop yield and different nitrogen(N)loss pathways and greenhouse gas emissions,this paper observed crop N uptake,NH3 volatilization,N2O emission and leaching N in the North China Plain.We also try to observe the effect of fertilization way,substitution of chemical fertilizer nitrogen by manure and winter cover crops on reactive N emissions in the North China Plain,and then we analyze nitrogen surplus and nitrogen balance.The main conclusions are as follows:(1)Compared with conventional fertilization(urea)and same-row planting techniques,wide-narrow row with high ridge(banding)and slow-controlled release fertilizer could ensure maize yield.The wide-narrow row with high ridge technology increased nitrogen use efficiency(NUE)by 36.4%under application of urea,and slow-controlled release fertilizer increased NUE by 5.45%under the technology of wide-narrow row with high ridge.The wide-narrow row with high ridge technology and slow-controlled release fertilizer both reduced N surplus,and thus may reduce the risk of N loss.The ammonia volatilization coefficient of wide-narrow row with high ridge was lower than that of same-row planting techniques,and the ammonia volatilization coefficient of slow-controlled fertilizer was lower than that of urea.Compared with urea combined with same-row planting,the technologies of wide-narrow row with high ridge + urea and wide-narrow row with high ridge +slow-controlled fertilizer both reduced N2O emissions,but had no significant impact on CO2 emissions.(2)The long-term application of pig manure and chicken manure in 50%substitution of chemical fertilizer nitrogen increased maize yield,soil SOC and TN content in the North China Plain.Compared with NPK treatment,NPKC and NPKP increased NUE by 28.7%and 25.0%,respectively,but decreased N surplus by 34.2%and 29.8%,respectively.The main loss pathways were N leaching and NH3 volatilization.The NH3 volatilization and N leaching from a maize system after a long-term livestock manure incorporation was decreased on a crop-yield basis,but CO2 and N2O emissions could not be reduced.(3)The soil SOC,TN,soil microbial activity and maize yield were improved in the winter cover crop-spring maize rotation system.In spring maize growing season,the nitrogen surplus of treatments with cover crops were ranged from 27.0 to 41.6 kg·ha-1.In the winter fallow field-maize treatment,the loss ways from spring maize growing season were NH3 emissions and N leaching,and NH3 emissions accounted for 33.5%of the nitrogen surplus,and leaching nitrogen loss accounted for 16.6%in bare land-spring maize system,which were lower than those of the cover crop-spring maize system.In maize growing season,the incorporation of cover crop combined with chemical fertilizer decreased NO3-leaching,but had no significant effect on NH3 emissions.In the long run,the incorporation of cover crop as a substitution of N fertilizers partially may reduce the environmental risk caused by nitrogen loss.