Keywords: 
• vegetable /
• orchard /
• nitrogen surplus benchmark /
• reactive nitrogen emission /
• greenhouse gas emission /
• Hainan

Abstract: This study aims to quantify the nitrogen （N） input and output of Hainan’s tropical vegetable and orchard cropping systems,establish N surplus indicators,and evaluate the environmental impacts.We collected 34 papers published in Hainan since 1980,including 72 samples of conventional and optimized N management of vegetables and orchards.The N inputs,outputs,and surpluses under conventional and optimized N management were analyzed based on the soil surface nitrogen balance method,and the N surplus under the optimized management was used as the N surplus benchmark.The life cycle assessment method （LCA） was used to quantify reactive N losses,greenhouse gas emissions,carbon and N footprints under conventional and optimized N management.Under conventional N management,the N surpluses were 290 kg·hm^-2 in vegetables and 432 kg·hm^-2 in orchards,respectively,the corresponding N surplus benchmarks under optimized N management were reduced by 39%and 49%,which were 176 and 222 kg·hm^-2,respectively.The reactive N emission,N footprint,greenhouse gas emissions（CO₂-eq）,and carbon footprint（CO₂-eq） under conventional N management of vegetables were 145 kg·hm^-2,4.5 kg·t^-1,9 444 kg hm^-2 and 295 kg·t^-1,respectively;under optimized N management,the above indicators were reduced by 26%,24%,19%and 19%,respectively.The active N emission,N footprint,greenhouse gas emission,and carbon footprint under conventional N management of orchards were 177 kg·hm^-2,4.5 kg·t^-1,14 758 kg·hm^-2 and 388 kg·eq t^-1,respectively;Optimizing N management can reduce the above indicators by 28%,33%,21%and 26%,respectively.In conclusion,the N surplus benchmarks of Hainan’s typical vegetable and orchard systems were 176 and 222 kg·hm^-2,respectively,using optimized N management （such as"4R Plus"nutrient management strategy,soil acid modification and organic carbon improvement,fertigation,etc.） can achieve the above N surplus benchmarks,and the current reactive N emissions,N footprint,greenhouse gas emissions,and carbon footprints can be reduced by 19%-33%.