Effects Of Reduced Nitrogen Fertilizer And Nitrification Inhibitor On Yield And N-₂0 And NO Emission In Vegetable Fields

The proportion of vegetable production in the whole agricultural production is getting larger and larger with the increase of people's living standard and demand.The characteristics of high intensification,high multiple crop index and large amount of fertilization of planting vegetables caused a large number of Nitrous oxide(N2O)and Nitric oxide(NO)emissions from vegetable soil,so that vegetable ecosystem has become an important N2O and NO source in the farmland.A field experiment with 6 consecutive vegetable crops was conducted in a continuously cultivated vegetable cropping system in Nanjing to investigate the effects of reduced N dose and a kind of nitrification inhibitor(CP)on vegetable yields,nitrogen use efficiency,N2O and NO emissions,yield-scaled N2O and NO emissions under different N application rates which contain control(CK)reduced N dose(Nr)and the normal N dose(Nn)by using static chamber-gas chromatography from December 2014 to July 2016.NO fluxes of each treatment were monitored continuously by using static chamber-NOx analysis meter from September 2015 to July 2016.Effects of were studied.The main results were listed as follows:(1)Nr reduced the concentration of soil NH4+-N and NO3--N while CP significantly inhibited the transformation of soil NH4+-N to NO3--N,thus maintain a high level of soil NH4+-N concentration in vegetable soil.Compared with Nn treatment,Nr treatment did not significantly affect the yield with or without CP,but the N partial factor productivity(PFPN)was significantly increased due to the decrease nitrogen fertilizer amount.The effects of the amount of nitrogen applied on the yield of vegetables were different in each vegetable season,but yield of CK treatment was lowest across the 6 vegetable seasons.CP did not significantly affect the yield,thus did not significantly affect the PFPN.(2)Vegetable field is an important source of N2O emissions.The N fertilization increased N2O emissions.Seasonal variation of N2O fluxes of all treatments showed the same pattern,but they were different in various vegetable seasons.N2O fluxes varied 0.5?6424.6?g N m-2 h-1.Compared with Nn,Nr reduced cumulative N2O emissions by 23.4%and 24.8%with and without CP,respectively.The N2O fluxes of CP treatments were lower than treatments without CP.The application of CP decreased the total N2O emissions by 23.4%and 24.8%,respectively,and it also significantly decreased N2O emission factors from 3.4?3.6%to 1.6?2.3%under Nr and Nn.Compared with Nn treatment,Nr treatment did not significantly reduced the yield-scaled N2O emissions in CP-N treatments.CP significantly reduced the yield-scaled N2O emissions in vegetable cropland.For Nr and Nn,CP inhibited the yield-scaled N2O emissions by 31.3%and 29.7%,respectively.(3)The NO fluxes of the each treatment showed obvious seasonal variation,and the NO emission from different vegetable season was different.The N fertilization increased NO emissions during the entire observation period,and the Nr treatment reduced cumulative NO emissions by 33.0%and 11.7%with and without CP,respectively.The application of CP reduced cumulative N2O emissions by 26.8%and 44.5%,respectively,and it also significantly decreased N2O emission factors from 0.30?0.41%to 0.12?0.13%under Nr and Nn,which because CP can directly the inhibit nitrification process,and thus decrease the NO emission.Compared with Nn treatment,Nr treatment did not significantly reduced the yield scaled NO emissions in CP-N treatments.CP significantly reduced the yield scaled NO emissions.For Nr and Nn,CP decreased the yield-scaled NO emissions by 31.4%and 47.9%,respectively.(4)Compared with Nn treatment,Nr treatment significantly reduced the yield-scaled N2O and NO emissions by 13.5%(P<0.05),but did not significantly reduced the yield scaled N2O and NO emissions in CP-N treatments.Meanwhile,the yield-scaled N2O emission and the yield-scaled NO emission was high in the CK treatment,which probably be due to the yield of CK treatment is relatively low.In addition,CP significantly reduced the yield-scaled N2O emissions and the yield-scaled NO emissions in vegetable cropland,thus significantly decreased the yield-scaled N2O and NO emissions.In this experiment,reduction of one third of the amount of nitrogen fertilizer did not significantly affect the yield of vegetable,but increased the PFPN and significantly reducing the N2O and NO emissions,and thus reduced the yield-scaled N2O emissions and the yield-scaled NO emissions.CP decreased the N2O and NO emission and maintaining vegetable production in intensive vegetable cropland.It is a recommended to combine practices of reducing nitrogen fertilizer and CP was the best in intensive vegetable production.