Environmental Impacts,Mitigation Potentials And Management Approaches In Chinese Vegetable Production System

China has the largest vegetable production in the world.Chinese intensive vegetable system is characterized as a high-input and high-output system with serious environment risks.It is critical to achieve the vegetable sustainable development by analyzing the environmental impacts and greenhouse gas mitigation potentials through a proper management approach in Chinese vegetable production system.Therefore,the objectives of this study were 1)to establish the reactive nitrogen loss model for Chinese vegetable system using a meta-analysis;2)to quantify the nutrient inputs and environmental impacts of Chinese pepper production,as well as the variation between different regions,using the life cycle assessment(LCA)for local emission factors based on 538 farmer survey data;3)to further quantify the mitigation potentials of Chinese pepper production system through analyzing the different farmers' groups in a same region;4)to establish the Integrated Soil-crop System Management(IS SM)in vegetable production system,and 5)to validate the comprehensive effect of the ISSM on yield and environment through a two-year field experiment.The main results were summarized as follows:1.Based on results of the meta-analysis,the reactive nitrogen loss model for Chinese vegetable system has been established.Nitrous oxide(N2O)emissions and nitrate leaching linearly increased with fertilizer N rate in Chinese vegetable production system,with mean values of 3.91 kg N2O-N ha-1 and 79.1 kg N ha-1,for N2O emissions and nitrate leaching,respectively.N2O emission and nitrate leaching were significantly greater in the greenhouse than in the open-field system.The emission factors(EFs)for N2O emissions were similar between the greenhouse and the open-field systems,whereas the leaching factors for nitrate leaching were significantly lower in the greenhouse than in the open-field system.2 Based on the local emission factor determined using the life cycle assessment(LCA)for 538 farmer survey data,the area-based mean potentials for reactive N loss,global warming,acidification,and eutrophication of Chinese pepper production were 120 kg N ha-1,5656 CO2-eq ha-1,48.8 PO4-eq ha-1 and 79.3 kg SO2-eq ha-1,respectively.The yield-based mean potentials for reactive N loss,global warming,acidification,and eutrophication were 6.15 kg N t-1,287 C02-eq t-1,2.51 PO4-eq t-1 and 4.14 kg SO2-eq t-1,respectively.Environmental impacts differed among regions of Chinese pepper production systems.On both area and yield basis,environmental impacts followed the order of:South region>North region>Northwest region>Yangtze River basin>Southwest region;Northwest>North regions>Southwest regions>South region>Yangtze River basin.3 Based on the analysis of different farmers' groups in the same region,environmental impacts of fertilizer management differed among farmers in Chinese pepper production systems.For Southwest pepper production system in China,the mean potentials for global warming,eutrophication,and acidification in the high yield and high PFP-N(HH)group were lower by 37.3%,34.4%and 33.9%,respectively,compared to the regional average.Meanwhile,yields in the HH group were 35.0%higher.For Yangtze River Basin pepper production system,the mean potentials for global warming,acidification,and eutrophication in top 25%of the pepper yields group were lower by 23.9%,25.0%,and 25.7%,respectively,compared to the regional average.Meanwhile,yields in the top group were 26.6%higher.These results clearly showed that environmental costs could be significantly mitigated through integrated nutrient-crop management strategies in vegetable production based on farmers' practice.4 The Integrated Soil-crop System Management(ISSM)have been designed through optimizing the soil management,crop population design,and nutrient management in pepper production under greenhouse system in Yangtze River Basin.A two-year field experiment was conducted for the validation.Results showed that compared to famers' current practices,ISSM reduced N application rate by 54.5%,increased pepper yields by 16.3%.On yield basis,the potentials for the reactive nitrogen loss,global warming,acidification and eutrophication were reduced by 59.5%,37.5%,51.2%and 59.1%,respectively.