地表滴灌条件下土壤湿润体运移量化表征

基于非饱和土壤水分运动的Richards方程,采用HYDRUS-2D/3D模拟软件对11种典型土质(美国制土壤质地分类系统)中滴灌湿润体的运动过程进行了数值模拟。结果表明,湿润体平均含水率的增量与滴灌流量正相关,与饱和导水率负相关;湿润体垂向迁移距离与滴头流量、饱和导水率和时间呈幂函数关系;湿润体径向迁移距离可用滴头流量、平均含水率的增量、垂向迁移距离和时间来定量表征。据此建立了描述不同土质中湿润体动态变化规律的经验公式,通过与数值模拟结果、文献试验数据等进行对比,表明此经验公式对不同土质中湿润体运移规律的预测效果较好,可为农业生产中地表滴灌设计提供简便实用的计算工具。

Quantification of Soil Wetted Volume Development under Surface Drip Irrigation

Understanding the behavior of soil wetted volume evolution in drip irrigation is essential for improving agricultural water use efficiency and realizing precision irrigation. Based on the Richard equation for water movement in unsaturated soil, the HYDRUS-2D/3D model was used to numerically simulate the soil wetting pattern in 11 kinds of typical soils (USST). Results showed that soil water content increment in wetted volume was in a positive correlation with the dripper discharge rate, and in a negative correlation with the saturated soil hydraulic conductivity. The advancement of vertical wetting front can be quantified by the selected influencing factors, i.e., the dripper discharge, saturated hydraulic conductivity and irrigation time. The horizontal wetting front can be expressed by the dripper discharge, soil water content increment in wetted volume, vertical wetting front and irrigation time. Then two empirical equations were formulated to describe the development of soil wetted volume under different dripper discharge, saturated hydraulic conductivity and irrigation time. By comparing with the numerical simulation results and the experimental data from literatures, it showed that the empirical formulas were reliable for predicting the migration of soil water in drip irrigation for different kinds of soil textures and managing to be a convenient and practical tool for the design of surface drip irrigation in agricultural activity.