压力水头对微润灌溉土壤水分运移试验研究

为了探明微润灌溉湿润体特性,采用黏性土壤和3个水头(1.5,2.0,2.5 m)进行试验,分析微润管的入渗速率、累计入渗量、湿润体体积及湿润体含水率分布特征,同时探讨了含沙量为1.0 g/L的水质在3种水头压力下的堵塞问题.研究表明:土壤累积入渗量与压力水头呈正相关,与时间呈负相关;粒径为0.061~0.100 mm的浑水试验中,试验初期3个不同水头下的流量相差较小,24 h后流量相差逐渐增大,压力水头增大对微润带的堵塞情况有改善作用;微润灌溉湿润体形状近似圆柱状,湿润锋行进半径与压力水头呈正相关,建立了压力水头与湿润体体积的预测模型;不同压力水头下各方向的湿润锋扩散指数都约为0.42;湿润体体内含水率呈同心圆分布,随半径增大而减小,靠近微润管壁2 mm处含水率最大,土壤水分移动主要动力为压力水头和土壤势能之差.研究结果可为微润灌溉提供科学的理论依据和理论基础.

Experimental study of pressure head on water migration in soil under moistube-irrigation

Characteristics of wet body under moistube-irrigation were clarified experimentally based on clay loam soil in the paper. Three pressure heads(1.5, 2.0 and 2.5 m)were used in our experiments to identify infiltration rate, cumulative infiltration, wet body volume and water content distribution cha-racteristics. Additionally, the clogging performance of moistube was addressed by using the water with 1.0 g/L sediment content under these pressures. Results show that the cumulative infiltration of the soil is positively correlated with pressure head but negatively correlated with time. In the muddy water experiment with 0.061-0.100 mm sediment particle diameters, the pressure head is positively correlated with flow rate. In the initial period of the experiment, however, the flow rate under one pressure head differs little from that under another pressure head. Just after 24 hours, the flow rate exhibits a noticeable difference between different pressure heads gradually. This fact suggests that the increase of pressure head can improve the clogging performance of moistube. The wet body is like a cylinder, and wet front advancing radius is positively correlated with pressure head; particularly, a prediction model relating pressure head and wet body volume is established. The wet front diffusion indices in various directions are about 0.42 at various pressure heads. The water content distribution in a wet body is concentric; specially, the content decreases with increasing radius and has its maximum value at 2 mm from the moistube wall. The principal driving forces for water migration in the soil are pressure head and soil potential energy. These outcomes can provide theoretical basis in a scientific manner for moistube-irrigation.