Study On The Characteristics And Relationship Of Gaseous Nitrogen Loss From Plastic Greenhouse Vegetable Field Under Different Irrigation Conditions

The loss of gaseous nitrogen?N₂O,NO emissions,NH₃ volatilization,etc.?in greenhouse vegetable fields has become an environmental problem.Therefore,It is the realistic requirement of realizing the high-quality development of greenhouse vegetable fields in China that to reduce the loss of gaseous nitrogen under the effective supply of vegetables.At present,the research on the characteristics of various gaseous nitrogen in greenhouse vegetable fields under different irrigation conditions is not comprehensive.Moreover,the mechanism of gaseous nitrogen emission and the relation between them were not well understood.These problems has restricted the promotion and application of integrated control technology.In this paper,four treatments were set up in the typical greenhouse vegetable field in the suburbs of Beijing,including control fertilization?CK?,farmer's practice?FP?,farmer'practice with drip irrigation?FPD?and optimal fertilization with drip irrigation?OPTD?.Through the combination of field experiments and laboratory analysis,the characteristics of gaseous nitrogen loss were explored,the emission mechanism of N₂O,NO emission and NH₃ volatilization were analyzed,and the relationship between them were clarified.The main results were list as follows:?1?In terms of emission characteristics,N₂O,NO and NH₃ emission peaks were obvious appeared after fertilization and irrigation.The N₂O emission peak of each treatment lasted about 7 days in the basal fertilizer period,and lasted for 3?5 days in the top-dressing period.The peak value was235?2443?g m^-2h^-1.The NO emission peak duration is 2?6 days,and the peak value is 28?364?g m^-2 h^-1.The peak value of NH₃ volatilization was 0.15?3.68 kg ha^-1 d^-1,which reached the maximum value within 2?4 days after fertigation,and then gradually decreased with time.Air temperature,0?5cm soil temperature and 0?10cm WFPS were the main environmental factors that affected N₂O emission in cucumber season.Air temperature and 0?5cm soil temperature were the main environmental factors that affected NO emission and NH₃ volatilization in cucumber season.0?10cm WFPS were the main environmental factors that affected N₂O emission and NH₃ volatilization in tomato season.?2?In the whole cucumber tomato rotation period,the annual N₂O emission of each treatment was2.26,13.73,8.49 and 7.20 kg N ha^-1,respectively.The annual NO emissions of each treatment were 0.21,1.66,1.27 and 0.79 kg N ha^-1,respectively.The annual NH₃ volatilization of each treatment were 21.43,42.66,55.17 and 33.04 kg N ha^-1,respectively.Compared with FP,the accumulated N₂O emission of FPD treatment decreased by 45.3%and 31.7%,respectively,in cucumber season and tomato season?P<0.05?.The accumulated N₂O emission of OPTD treatment decreased by 44.5%and 50.5%,respectively,in cucumber season and tomato season?P<0.05?.Compared to FPD,OPTD did not increase the accumulated N₂O emissions.Compared with FP,FPD and OPTD reduced the accumulated NO emission by 35.4%and62.2%of cucumber in the season of topdressing,respectively.In tomato season,compared with FP,the accumulated NO emission of FPD treatment decreased by 8.6%?P<0.05?,and that of OPTD treatment decreased by 38.6%?P<0.05?.Compared with FPD,the accumulated NO emission of OPTD reduced by40.6%and 32.8%in cucumber and tomato seasons respectively?P<0.05?.Compared with FP,FPD significantly increased the cumulative loss of NH₃ volatilization in cucumber season by 45.0%?P<0.05?,and did not reduce the cumulative loss of NH₃ volatilization in tomato season.Compared with FPD treatment,the accumulated loss of NH₃ volatilization of OPTD in cucumber and tomato seasons reduced by 40.9%and 37.9%,respectively?P<0.05?.?3?The trends of N₂O and were similar in the whole cucumber tomato rotation.There was a positive linear correlation between N₂O and NO fluxes in greenhouse cucumber and tomato seasons?P<0.05 or P<0.01?.There was a positive linear correlation between N₂O fluxes and NH₃ volatilization rate in FP,FPD and optd treatments?P<0.01?.During the whole rotation period,the cumulative emission ratio of N₂O and NO was up to 11.7,and the total emission ratio of NH₃ and N₂O was up to 11.42.NH₃volatilization loss is the highest,followed by N₂O emission.In general,only changing the irrigation mode from the flood irrigation to drip irrigation significantly reduced N₂O and NO emission in greenhouse cucumber and tomato seasons,but did not reduce NH₃volatilization,and increased NH₃ volatilization loss in cucumber season.Therefore,it is necessary to comprehensively consider the interaction of different measures on N₂O,NO emission and NH₃volatilization.Changing the irrigation method while reducing the amount of fertilization not only ensures the yield of vegetables,but also has a significant emission reduction effect on N₂O,NO emission and NH₃volatilization,which is a recommended water and fertilizer management measure for vegetable field.