Establishment of Nitrogen surplus indicators in the main vegetable and orchard systems in Hainan
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%.
vegetableorchardnitrogen surplus benchmarkreactive nitrogen emissiongreenhouse gas emissionHainan
NETL
NSTL
万方数据
