垄沟灌溉施氮土壤水氮分布特征试验研究

Experiment on water and nitrogen distribution in soils under ridge-furrow irrigation with ammonium nitrate solution

为了指导垄沟间(套)作种植田间灌水技术和灌溉系统合理设计,通过长方体土槽模拟垄沟灌溉施氮二维土壤入渗试验,探究4种土壤质地的入渗量随时间变化规律,分析肥液入渗湿润体特征,研究土壤水分、硝态氮和铵态氮空间分布特征.结果表明,随着土壤黏粒含量的增多,土壤比表面积增大,在相同灌水时间内入渗量则小;入渗量累积曲线上升趋势因土壤质地不同存在显著差异.含3参数的Horton入渗模型计算的肥液入渗量精度高,其稳定入渗率参数实用性强,对灌水流量设计有重要的参考价值.随着土壤砂粒含量的增多,同等入渗条件下,湿润锋运移距离越远,且垂向运移距离均大于水平侧渗距离.水平侧渗距离与入渗时间呈指数函数关系,垂向湿润锋运移距离与入渗时间的1/2次方呈线性函数关系.垄沟灌溉施氮方式下,硝态氮在湿润锋边缘累积,铵态氮峰值出现在灌水沟附近.在质地重的土壤下应用垄沟灌溉施肥技术好.

In order to provide guidance to reasonable design of irrigation technique and system in ridge-furrow intercropping fields,the infiltration characteristics and soil water and nitrogen distributions in four soil textures under ridge-furrow irrigation with ammonium nitrate solution were investigated in laboratory experimentally by using rectangular soil chambers to simulate the two-dimensional infiltration in the irrigation.The distributions of water,nitrate,and ammonium in the soils were clarified.The soil wetting front was also recorded against infiltration time.The results showed that the cumulative infiltration of fertilizer solution and its infiltration rate tend to decrease with increase in clay content of soil texture because of greater soil specific surface area.Note that the increasing slope of the cumulative infiltration curve is significantly dependent of soil texture.The Horton infiltration model with three underdetermined parameters is fairy precise in estimating infiltration of fertilizer solution,in which the steady-state infiltration rate has very practical and is one important reference quantity for determining the flow rate in ridge-furrow irrigation.The wetted front migrates far away in the lateral and vertical directions in coarser soils at the same infiltration condition,the vertically wetted distance is longer than the laterally wetted one,and the wetted front is like an ellipsoid with a long axis in the vertical direction.The relation of laterally wetted distance to infiltration time can be described by an exponential function,while the vertically wetted distance has a linear relation to the square root of infiltration time.It was illustrated that the nitrate accumulates on the boundary of wetted front,but the highest ammo-nium concentration appears near furrows.The ridge-furrow fertigation technique should be implemented in finer soils to reduce deep percolation of water and nutrients below the root zone and improve water and fertilizer use efficiency in ridge-furrow intercropping fields.