降雨、施肥对补水河流周边土壤硝态氮迁移分布的影响

Effects of rainfall and fertilization on soil nitrate nitrogen migration-distribu-tion around water replenishing rivers

补水河流周边土壤硝态氮迁移过程受到河流水文条件、降雨、施肥等多因素的影响,研究多种因素共同作用下土壤硝态氮分布及淋失特征,可以为深入理解土壤氮素循环过程奠定基础。本研究以华北平原白洋淀入淀河流周边农田和农林复合区(AF)为研究对象,其中农田区设置不施肥(CK)、优化施肥(YH)、习惯施肥(XG)3个施肥处理,综合分析在不同降雨类型、生态补水等因素作用下土壤硝态氮剖面分布、淋溶等迁移特征。研究结果表明:施氮量、降雨类型、生态补水等均是影响补水河流周边硝态氮迁移淋失的关键因子。其中,施氮量决定土壤硝态氮淋失总量(P<0.01)。随着施氮量的增加,土壤剖面的硝态氮含量和硝态氮淋失量均显著增加,与XG处理相比,YH处理和AF处理的硝态氮淋失总量分别减少40.6%和40.1%。降雨和生态补水改变了硝态氮在土壤剖面的迁移过程。其中,降雨主要影响表层土壤硝态氮向中下层迁移,生态补水主要影响中下层土壤硝态氮向更深层土壤的迁移。另外,不同降雨类型对土壤硝态氮迁移的影响有所差异,即两种降雨类型下硝态氮向下层土壤迁移速率和迁移量不同。常规降雨(3 d累积降雨65.2 mm)和强降雨(5 h累积降雨49.2 mm)两种情况下硝态氮累积峰均在40~60 cm土层。常规降雨导致XG处理40~60 cm比0~40 cm土层硝态氮储量增加9.7%;强降雨导致XG处理40~60 cm比0~40 cm土层硝态氮储量增加16.7%。生态补水导致YH处理和XG处理在100~140 cm土层硝态氮储量分别减少42.7 kg·hm^(-2)和39.6 kg·hm^(-2)。以上研究结果对于生态补水和极端降雨背景下土壤氮素污染管理具有重要意义。

Soil nitrate-nitrogen migration around recharge rivers is affected by multiple factors,such as the hydrological condition of the rivers,rainfall,and fertilization.The study of soil nitrate-nitrogen distribution and leaching characteristics under the joint action of multiple factors can lay the foundation for an in-depth understanding of the soil nitrogen cycling process.In this study,we used farm-lands and agroforestry composite region(AF)around the Baiyangdian River on the North China Plain as the research focus.The farmland area was set up with three fertilization treatments-no fertilization(CK),optimized fertilization(YH),and conventional fertilization(XG).The distribution of nitrate-nitrogen along soil profile and leaching characteristics under different types of rainfall and ecological recharge,and other factors were comprehensively analyzed.The results showed that nitrogen application,rainfall type,and ecological water recharge were the key factors influencing nitrate-nitrogen migration around the recharged river.The amount of applied nitrogen determined the total amount of leached soil nitrate-nitrogen(P<0.01).With the increase in nitrogen application,the nitrate-nitrogen content and nitrate-nitrogen leaching within the soil profile increased significantly.The total nitrate-nitrogen loss of YH treatment decreased by 40.6%compared with XG treatment,and the total nitrate-nitrogen leaching loss in the AF treatment de-creased by 40.1%.Rainfall and ecological recharge altered the migration of nitrate-nitrogen in the soil profile.Rainfall mainly af-fected the migration of nitrate-nitrogen from the surface to the middle and lower soil layers,and ecological recharge mainly affected the migration of nitrate-nitrogen from the middle and lower layers of the soil to the lower layers.In addition,the effects of different rainfall types on the migration of soil nitrate-nitrogen varied.The migration rate and amount of nitrate-nitrogen in the lower layer of the soil differed between two rainfall intensities.The peak of nitrate-nitrogen accumulation was in the 40-60 cm soil layer during both regular and heavy rainfall.Regular rainfall(3 d cumulative rainfall of 65.2 mm)resulted in an increase of 12.4 kg·hm^(−2)(9.7%)in ni-trate-nitrogen storage in the 40−60 cm soil layer with XG treatment(compared with the 0−40 cm layer),while heavy rainfall(5 h cu-mulative rainfall of 49.2 mm)resulted in an increase of 16.3 kg·hm^(−2)(16.7%)in nitrate-nitrogen storage in the 40−60 cm soil layer with XG treatment.Ecological recharge resulted in a reduction of nitrate-nitrogen storage by 42.7 kg·hm^(−2) and 39.6 kg·hm^(−2) in the 100−140 cm soil layer with the YH and XG treatments,respectively.These findings have important implications for managing soil ni-trogen pollution in the context of ecological recharge and extreme rainfall.