海南典型稻菜轮作区和香蕉园氮磷盈余及土壤硝态氮累积

Nitrogen and Phosphorus Surplus and Soil Nitrate Nitrogen Accumulation in Typical Rice-Vegetable Rotation and Banana Garden in Hainan

【目的】海南省是我国稻菜轮作和香蕉种植面积较大的省份,农户投入的氮(N)和磷(P)肥远超过了作物的养分需求,对海南生态环境可能造成不利影响。研究海南典型作物体系氮磷输入、输出、盈余及土壤硝态氮累积,为评价其养分损失及环境影响、提高养分管理水平提供科学依据。【方法】2021—2022年选取海南稻菜轮作和香蕉种植典型区域澄迈县为研究区,确定20个稻菜轮作田块和15个香蕉园。采用跟踪记录的方法获取所有地块的化肥施用量、有机肥施用量和秸秆还田方式及还田量等信息。采用跟踪采样的方法测定作物生物量及其养分含量。采用文献调研的方法获取研究区域土壤-作物体系养分沉降和生物固氮等其他来源数据。选取5个旱地香蕉园,采用土钻法采集土壤并测定0—400 cm土壤剖面硝态氮累积量。【结果】海南典型稻菜轮作区氮肥和磷肥投入量分别为1308 kg N·hm^(-2)(化肥和有机肥分别为975和333 kg N·hm^(-2))和515 kg P·hm^(-2)(化肥和有机肥分别为385和130 kg P·hm^(-2)),作物地上部吸氮量和吸磷量分别为248 kg N·hm^(-2)和48 kg P·hm^(-2),稻菜轮作区氮素和磷素盈余分别为1196 kg N·hm^(-2)和484 kg P·hm^(-2)。香蕉园氮肥和磷肥投入量分别为1340 kg N·hm^(-2)(化肥和有机肥分别为1293和47 kg N·hm^(-2))和447 kg P·hm^(-2)(化肥和有机肥分别为442和5 kg P·hm^(-2)),香蕉地上部吸氮量和吸磷量分别为242 kg N·hm^(-2)和23 kg P·hm^(-2),氮素和磷素盈余分别为1271 kg N·hm^(-2)和435 kg P·hm^(-2)。香蕉园0—400 cm土壤剖面硝态氮累积量为1131 kg N·hm^(-2)。【结论】过量施用氮肥和磷肥,导致海南典型区土壤-作物体系存在大量的养分盈余,旱地土壤也累积了大量的硝态氮。海南以较大的养分损失和环境代价生产热带高值水果和蔬菜,未来必须优化农田养分管理措施以保障其生态环境安全。

【Objective】Hainan is the province with a large area of rice-vegetable rotation and banana cultivation in China,but the nitrogen(N)and phosphorus(P)fertilizers input by farmers far exceed the nutrient requirements of crops,which may have a negative impact on Hainan's ecological environment.The aim of this study was to investigate the N and P surpluses,and soil nitrate accumulation in typical cropping systems in Hainan,thus to provide scientific basis for evaluating nutrient losses and their impacts and achieving sustainable nutrient management.【Method】In 2021-2022,a typical area for rice-vegetable rotation and banana cultivation in Chengmai,Hainan,was selected as the research area and 20 rice-vegetable rotation plots and 15 banana orchards were identified.The information of chemical and organic fertilizer application,straw returning method and amount of above fields were obtained by real-time record of farmers'agricultural activities,crop biomass and the nutrient content were determined at crop harvest,and other nutrient input include nutrient deposition and biological N fixation were obtained by literature survey.Five banana orchards were selected and soil was collected by soil auger method and nitrate N accumulation was measured in the 0-400 cm soil profile.【Result】The N and P fertilizer inputs to the rice-vegetable rotation were 1308 kg N·hm^(-2)(975 kg N·hm^(-2)of chemical and 333 kg N·hm^(-2)of organic fertilizer)and 515 kg P·hm^(-2)(385 kg P·hm^(-2)of chemical and 130 kg P·hm^(-2)of organic fertilizer);the aboveground N and P uptake of the crop were 248 kg N·hm^(-2)and 48 kg P·hm^(-2);the surplus of N and P in rice and vegetable rotation was 1196 kg N·hm^(-2)and 484 kg P·hm^(-2).The N and P fertilizer inputs to banana orchards were 1340 kg N·hm^(-2)(1293 kg N·hm^(-2)of chemical and 47 kg N·hm^(-2)of organic fertilizer)and 447 kg P·hm^(-2)(442 kg P·hm^(-2)of chemical and 5 kg P·hm^(-2)of organic fertilizer);the aboveground N and P uptake were 242 kg N·hm^(-2)and 23 kg P·hm^(-2);the banana N and P surpluses were 1271 kg N·hm^(-2)and 435kg P·hm^(-2).The nitrate-N accumulation in the 0-400 cm soil profile of banana orchards was 1131 kg N·hm^(-2).【Conclusion】Excessive application of N and P fertilizers has led to the large nutrient surplus in typical soil-crop systems in Hainan,and large amount of nitrate-N has accumulated in banana orchard in the deep soil layer.Hainan produces typical high-value fruit and vegetables at the cost of large nutrient losses and negative environmental impacts,optimized nutrient management should be implemented to ensure its environmental safety.