The Agronimic And Environmental Effects Of Combining Nitrification Inhibitor Supply With Nitrogen Input Reduction On The Open-field Vegetable Cultivation In Southwest China

The problems of large amount of nitrogen(N)fertilizer and unreasonable nutrient input in open field vegetable production in Southwest China,coupled with regional high temperature and rainfall and serious soil weathering and leaching,lead to serious nitrogen loss and high environmental cost in vegetable system.Therefore,field trials were conducted and life cycle assessment(LCA)was used in this study.On the one hand,it quantitatively evaluated the effects of different N reduction combined with nitrification inhibitor(DMPSA)fertilizer products on the growth,development,agricultural,environmental and economic effects of Chinese cabbage and pepper in Southwest China.On the other hand,the influence of the theory and technology of soil-crop integrated management based on the combination of N reduction and DMPSA fertilizer products on the agronomic,environmental and economic effects of vegetable production in Southwest China was comprehensively evaluated.The main results are as follows:(1)The results showed that,compared with farmers’ conventional treatment,different N application rate reduction combined with DMPSA fertilizer products treatment had no significant effect on the Chinese cabbage growth and nutrient absorption under reduce about 62% of the N application rate.The total yield,commercial yield and N use efficiency of Chinese cabbage were increased by 4.2%～6.7%,9.0%～16.4% and 9.6%～11.2%,respectively.The average apparent N surplus,reactive N loss per unit yield,greenhouse gas emission,eutrophication effect and acidification effect were significantly reduced by 78.1%～78.8%,74.5%～74.9%,73.0%～73.5%,73.3%～73.8% and63.3%～63.9%,respectively.At the same time,the average economic benefit and net ecosystem economic benefit were significantly increased by 9.36%～16.6% and 110%～130% respectively,and the environmental cost per unit net ecosystem economic benefit was significantly reduced.There were no significant differences in growth,yield,nitrogen fertilizer efficiency,environmental cost and ecosystem economic benefits among the treatments of DMPSA calcium ammonium nitrate,urea and ammonium sulfate.The application of DMPSA calcium ammonium nitrate,urea and ammonium sulfate was beneficial to the sustainable production of Chinese cabbage.(2)The results showed that the application of different N reduction combined with DMPSA reduced the amount of N fertilizer by about 32% compared with farmers’ conventional treatment,whcih had no significant effect on the dry matter accumulation,nutrient absorption and yield of pepper.Compared with farmers’ conventional treatment,the apparent surplus of N decreased by 54.6% ～59.9%,N use efficiency increased by 9.30% ～ 13.7%,reactive N loss,greenhouse gas emissions per unit of production,and the effects of eutrophication effect and acidification effect were significantly reduced by 48.5% ～ 50.5%,45.6% ～ 47.7%,76.6% ～ 79.8% and 27.6% ～ 30.4% for different N application rate reduction with DMPSA fertilizer treatments respectively.The net ecosystem economic benefit of pepper production was increased by 0.73%～5.86%,and the potential environmental cost per unit net ecosystem economic benefit was significantly decreased by 19.6%～52.4%.In this study,there was no significant difference in the agricultural,environmental and economic effects of pepper production for the calcium ammonium nitrate,urea and ammonium sulfate combine with DMPSA treatments which were conducive to the sustainable production of pepper in Southwest China.(3)The results of experiments on five vegetables from seven experimental sites in different regions of Southwest China showed that compared with the conventional treatment of farmers,the soil-crop system integrated management strategy of reducing N combined with DMPSA could reduce the N fertilizer input by 50% on average,ensure the vegetable yield not to decrease,and the fertilizer use efficiency increase by 8.60%～26.3% on average.The average apparent N surplus of vegetable field decreased by 42.6%～94.4%,and the average active N loss of vegetable production,greenhouse gas emission,eutrophication potential and acidification potential per unit yield decreased by51.9%～77.5%,49.7%～75.1%,51.1%～76.9% and 32.4%～68.0%,respectively.Average gross revenue and net economic benefit increased by 6.58% and 12.5%,respectively.In addition,the average cost of environmental damage cost was significantly reduced by 64.2%,the net ecosystem economic benefit was significantly increased by 24.1%,and the average potential value of environmental cost per unit of ecological economic benefit was significantly decreased by 63.5%～74.1%.This comprehensive strategy can improve vegetable production efficiency,economic benefit and reduce environmental cost in southwest China,which is conducive to the sustainable production of vegetables.In summary,the management strategy of N application rate reduction combined with nitrification inhibitor(DMPSA)can increase yield and production efficiency,significantly reduce environmental costs,improve economic benefits and ecosystem economic benefits on main open-field vegetables,which is conducive to sustainable vegetable production in Southwest China.