滴灌施肥灌溉的水氮运移数学模拟及试验验证

Model verification of water and nitrate transport from a surface point source

基于土壤水分运动的动力学方程和溶质运移的对流-弥散方程,建立了不同土壤中地表滴灌施硝酸铵(NH4NO3)时水分和硝态氮运移的数学模型及边界条件。利用商业化软件HYDRUS-2D对模型进行了求解。为了验证所建立的模型,分别在壤土和砂土两种土壤上进行了不同滴头流量、灌水量和肥液浓度下的湿润距离、土壤含水率和硝态氮分布试验。模拟结果与试验数据的对比表明,利用HYDRUS-2D求解所建立的模型得到的湿润距离随时间的变化过程、土壤含水率和硝态氮分布与实测值吻合良好。因此,HYDRUS-2D软件可以作为预测滴灌施肥灌溉条件下水分和氮素在土壤中运移的有效工具。

A model simulating the transport of water and nitrate in soil from a surface point source of ammonium nitrate （NH4NO3 ） was established and solved numerically by using the HYDRUS-2D software. In the model, selected boundary conditions were used to describe the solute trasport for a medium-and a coarse-textured soil. The simulated wetting dimensions of soil volume and distributions of water content and nitrate concentrations in soil were compared with data obtained from laboratory experiments conducted on a loam and a sandy soil using various discharge rates, input concentrations, and applied volumes. Good agreement was obtained between simulated and measured wetting dimensions and water content as well as nitrate profiles. Simulations demonstrated that the nitrate accumulated toward the boundary of the wetted volume for any input concentration. It is concluded that the HYDRUS-2D software can be used to implement water and nitrate transport in soil under drip fertigation.