旱地农田氮磷淋溶发生特征研究进展

Research progress on the occurrence characteristics of nitrogen and phosphorus leaching in dryland farmland

氮磷淋溶是旱地农业面源污染的主要形式,直接导致水体污染风险尤其是地下水氮磷含量超标,明确氮磷淋溶发生特征是制定针对性措施阻控农田养分流失的前提条件。本文利用文献计量学方法分析了1984—2022年国际农田氮磷淋溶研究热点,论述当前主要淋溶监测方法及其优缺点,总结了影响淋溶的关键因素及其所带来的环境效应,探讨了氮磷淋溶研究存在的问题及未来研究方向。1984—2022年研究热点主要集中在不同水肥条件和管理方式下土壤氮素、磷素、硝酸盐等溶质的淋溶特征:NO_(3)^(−)-N为氮素淋溶主要形态;磷多以难溶颗粒态固持在土壤中,垂直迁移较少,但随着磷肥用量增加,淋溶逐渐成为磷损失的重要途径。当前的氮磷淋溶定量化方法主要包括原位实地监测和人工模拟降雨重塑淋溶过程,每种方法均有其优缺点,在研究过程中应当根据土壤、作物、目的等因地制宜地选择监测方法。受施肥、降雨灌溉、土壤类型和土地利用方式等因素影响,各地农田氮磷淋溶风险不一,主要农区肥料投入量大,土壤氮磷盈余量、地下水污染情况较其他地区更严重,环境风险仍十分严峻。未来面对极端气候变化,应在评估地下水硝酸盐污染程度的同时加强旱地深层土壤微生物过程、驱动机理研究,准确识别主要污染物类型从而进行针对防控,继续研发适合长期、连续和与自然条件相似的监测方法,综合运用原位监测、遥感、模型模拟等方法,量化同一区域内不同土地利用方式氮磷淋溶贡献,开展分类分区分级治理。

Nitrogen and phosphorus leaching is the main form of non-point source pollution in dryland agriculture,which directly leads to a risk of water pollution,especially excessive nitrogen and phosphorus content in groundwater.Clarifying the characteristics of nitrogen and phosphorus leaching is a prerequisite for formulating targeted measures to control farmland nutrient loss.In this study,by analyzing the relevant literatures,the research hotspots of nitrogen and phosphorus leaching in farmlands at home and abroad over the past two decades were clarified.The main leaching monitoring methods and their advantages and disadvantages were discussed,and the key factors affecting leaching and their environmental effects were summarized.Finally,the existing problems and future research directions for nitrogen and phosphorus leaching were discussed.In the past two decades,the leaching characteristics of soil nitrogen,phosphorus,nitrate,and other solutes under different water and fertilizer conditions and management methods have been eval-uated at home and abroad.Long-term excessive fertilizer input is the main reason for the accumulation and leaching of nitrogen and phosphorus in the soil.Long-term excessive fertilizer input leads to a surplus.Some nitrogen is discharged into the atmosphere along with ammonia,nitrous oxide,and other gases,whereas some nitrogen and phosphorus enter rivers and groundwater via runoff and leaching.NO_(3)^(−)-N is the main form of nitrogen leaching.Phosphorus is mostly immobilized in the soil in the form of insoluble particles,and there is less vertical migration.However,with the increase in phosphorus fertilizer use,leaching has gradually become an important mode of phosphorus loss.Current quantitative methods for nitrogen and phosphorus leaching mainly include in situ field monitoring and artificial simulation of the rainfall remodeling leaching process.Each method has its advantages and disadvantages.Monitoring methods should be selected according to local conditions such as soil,crops,and purpose.Affected by factors such as fertilization,rainfall irrigation,soil type,and land use,the risk of nitrogen and phosphorus leaching in farmlands varies from place to place.The amount of fertilizer input in the main agricultural areas is large,with a correspondingly large surplus of soil nitrogen and phosphorus,and the pollution of groundwater is more serious than in other areas,representing a serious environmental risk.In the face of extreme climate change,it is necessary to strengthen research on the microbial processes and driving mechanisms of deep soil in drylands while assessing the degree of nitrate pollution in groundwater and accurately identifying the main pollutant types for prevention and control.Moreover,it is important to continue to develop monitoring methods suitable for long-term,continuous,and similar natural conditions and to comprehensively use in situ monitoring,remote sensing,model simulation,and other methods to quantify the nitrogen and phosphorus leaching contribution of different land use patterns in the same area.Finally,classification,zoning,and grading management should be carried out.