Effects Of Irrigation And Nitrogen Fertilization Regulation On Soil Ammonia Volatilization And Its Influencing Factors In Greenhouse

NH₃ volatilization is one of the main form of nitrogen gas loss,and it is also one of the main reasons for the decline in the utilization of nitrogen fertilizer rate in farmland.With the increase of planting area year by year,and phenomenon of high nitrogen fertilizer input is very common in greenhouse production,the problem of ammonia volatilization in greenhouse soil gradually attracts more and more attention.Water and nitrogen are the most easily regulating and controlling factors in greenhouse production.Scientific irrgation and nitrogen management is of great practical significance for reducing excessive nitrogen fertilizer input,reducing fertilizer of ammonia volatilization loss,and preventing atmospheric environmental pollution.Based on a 6 consecutive years field positioning experiment of irrigation and nitrogen regulation in greenhouse.2-factor 3-level randomized block experiment design was conducted to study the effects of irrigation and nitrogen regulation on the emission characteristics of soil ammonia volatilization,related soil physical and chemical properties,and the influencing factors of ammonia volatilization using different irrigation lower limits?W₁:25k Pa,W₂:35k Pa,W₃:45k Pa?and nitrogen rates(N₁:75 kg N·hm^-2,N₂:300 kg N·hm^-2,N₃:525 kg N·hm^-2).Highresolution laser spectroscopy was used to measure the soil ammonia volatilization dynamics and environmental,soil physical and chemical and biological properties in greenhouse.The main findings are as follows:?1?The regulation of irrigation and nitrogen significantly affected the soil physical and chemical properties,and the interactive effects of irrgation and nitrogen significantly affected the soil temperature and moisture.Soil p H decreased with the increase of nitrogen application rates,and the soil Eh decreased with the increase of the irrigation lower limit.The interactive effects of irrigation and nitrogen had the grestest effect on soil average CEC and EC content.Different combinations of irrigation lower limits and nitrogen rates had different dynamic changes of p H,Eh,and CEC.W₁N₁ treatment was the highest for soil p H and Eh,and the CEC of W₂N₁ treatment was the highest.The surface soil ammonium content increased with the increasing of nitrogen application rates.The average content of NO₃^--N,TSN,and SON were significantly affected by the single nitrogen rate at different fertilization periods,and the interaction effects of irrigation and nitrogen and single irrigation lower limits on them had different significance at different fertilization periods,but the three peaks all appeared in W₂N₃ treatment.Nitrogen rates and the interactive effects of irrigation and nitrogen significantly affected soil total nitrogen,total organic carbon and C/N.The interactive effects of irrigation and nitrogen significantly affected the soil urease activity,amidase activity and L-asparaginase average activity during top dressing stage.?2?The irrigation lower limits,nitrogen rates,and their interactions had extremely significant effects on the peak of ammonia volatilization flux,cumulative volatilization,cumulative ammonia volatilization yield,ammonia volatilization loss rate,and tomato yield in greenhouse soil.The maximum tomato yield in W₁N₃ treatment was 123.36 t · hm^-2.The empirical statistical S model can better fit the changes of soil ammonia volatilization during different fertilization periods in greenhouse tomatoes.The characteristic parameters of ammonia volatilization in the basal fertilizer stage were mainly affected by the irrigation lower limits and the interaction of irrigation and nitrogen.The characteristic parameters of ammonia volatilization during the top dressing period were mainly influenced by the single nitrogen rates and the interaction of irrigation and nitrogen.In this study,the nitrogen loss rate ranged from 0% to 2%,and the nitrogen loss caused by ammonia volatilization was relatively low.Compared with the soil fertilization?basal fertilizer?mode,the drip irrigation fertilization?top dressing?mode can significantly reduce ammonia volatilization by 94.78%⁹6.30%.?3?Soil ammonia volatilization was closely related to the environment and soil factors,and it indicated different influencing effects at different fertilization periods.NH₄⁺-N,NO₃^--N,soluble total nitrogen,soil urease activity,amidase and L-asparaginase activity were significantly influencing factors on ammonia volatilization flux in both basal and top dressing stages,which showed a significant negatively correlated with amidase and L-asparaginase activities,and nificant positive correlation with other indicators?P <0.05?.In addition,the peak flux of soil ammonia volatilization in the basal fertilizer stage was significantly positively correlated with the greenhouse temperature,p H and CEC,but negatively correlated with Eh.During the top dressing stage,ammonia volatilization flux was significantly negatively correlated with EC and soluble organic nitrogen,and significantly positively correlated with Eh and CEC.The stepwise regression model with environment and soil factors as explanatory variables could explain 73.9% 99.3% of the variation of ammonia volatilization of different irrigation and nitrogen treatment.Ammonium nitrogen was an important factor affecting ammonia volatilization flux under different irrigation and nitrogen treatments.Comprehensive analysis of nitrogen fertilizer input,yield and environmental and soilfactors affecting ammonia volatilization,nitrogen rate of 300 kg N · hm-2 combined with theirrigation lower limit of 25 k Pa?W1N2?was most suitable for economic and environmentalbenefits,and it was the best irrigation and nitrogen management model to coordinate ammoniavolatilization loss and tomato yield.