不同水头压力的微润灌对土壤水盐运移的影响

为探明微润灌对土壤水盐运移的影响,以南疆盐碱土微润灌为研究对象,采用室内模拟试验,分析了不同水头压力(1、1.5、2、2.5 m)条件下微润灌土壤水盐分布特征。结果表明,水头压力较低,水分水平扩散距离较小,土壤湿润区形状明显为椭圆形,随着水头压力的增大,水分水平扩散距离与垂直入渗距离逐渐接近,湿润区形状呈现由椭圆形向圆形转化的趋势;不同水头压力下湿润区位置均表现为在水平方向上以微润带埋设位置为中心,呈左右对称关系;垂直方向上土壤湿润区主要集中在微润带以下位置;提高水头压力,可以有效增大土壤湿润区面积及湿润体内土壤含水率;不同水头压力下均表现为以微润带为中心,形成土壤脱盐区,土壤盐分聚集在湿润锋附近;低水头处理,湿润区内土壤得不到有效淋洗,土壤脱盐区面积较小及脱盐率相对较低;高水头处理,盐分随水分运移至表层和深层土壤,扩大了土壤脱盐区面积,并且提高了土壤脱盐率,水头压力越高,该现象越明显。

Impact of Water Pressure on Water Flow and Salt Movement in Soil under Moistube Irrigation

Taking the salinized soil in south of Xinjiang as an example, we experimentally investigated water flow and salt movement in soil under moistube irrigation at different water pressures (1 m, 1.5 m, 2 m and 2.5 m water head, respectively) in laboratory. The results showed that at low water pressure, the spatial distribution of water in the soil was elliptical. With water pressure increasing, the impact of gravity fades away and the distances the water moved in the vertical and the horizontal directions were close and the spatial distribution of water was approximately circular. Under all water pressures, the soil moisture distributions were spatially symmetric around the vertical line crossing where the moistube was located, with the soil just underneath the moistube mostly wet-ted. Increasing water pressure led to an increase in wetting area and soil moisture content. Under all water pres-sures, the soil in the wetting zone was desalinized and the dissolved salt accumulated at the wetting fronts. Under low water pressure, however, only part of the salt within the wetting zone was dissolved and leached. With water pressure increasing, the dissolved salt was leached to deep soil and moved upward to the surface soil.