摘要
为了定量海南热带蔬菜和果树体系氮素输入和输出,建立氮素盈余指标并评价其环境影响,搜集了1980年以来发表的有关海南农田的34篇符合要求的文献,包括蔬菜和果树传统和优化氮素管理的72个样本,用土壤界面氮素平衡法分析氮素输入、输出和盈余,并以优化管理下氮素盈余作为氮素盈余阈值.同时,用生命周期评价法(Life Cycle Assessment)定量活性氮损失、温室气体排放、碳和氮足迹.结果表明:传统氮素管理条件下,海南典型蔬菜和果树氮素(N)盈余分别为290和432 kg·hm-2;优化氮素管理条件下,对应氮素盈余(阈值)减少39%和49%,分别为176和222 kg·hm-2;蔬菜传统氮素管理下活性氮排放、氮足迹、温室气体排放(CO2-eq)和碳足迹(CO2-eq)分别为145 kg·hm-2、4.5 kg·t-1、9 444 kg·hm-2和295 kg·t-1,优化氮素管理分别减少以上指标的26%、24%、19%和19%;果树传统氮素管理下活性氮排放、氮足迹、温室气体排放和碳足迹分别为177 kg·hm-2、4.5 kg·t-1、14 758 g·hm-2和388 kg·t-1,优化氮素管理分别减少以上指标的28%、33%、21%和26%.综上所述,海南典型蔬菜和果树体系氮素盈余阈值分别为176和222 kg·hm-2,采用优化模式(如"4R Plus"养分管理策略、土壤"改酸增碳"和水肥一体化等)可以达到以上氮素盈余阈值,并降低当前活性氮排放、氮足迹、温室气体排放和碳足迹的19%～33%.
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%.
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