滴灌条件下层状土壤滞盐作用的试验研究

Retardation Effect of Layered Soil to Salt Transfer under Drip Irrigation

为了探讨滴灌条件下黏土夹层在层状土壤中的滞盐作用,针对不同构型的层状土壤进行土柱滴灌入渗试验,试验中,均质土壤为松沙土和轻壤土;层状土构型为松沙土夹轻黏土和轻壤土夹轻黏土;其中,均质土柱灌水量分别为88.5、106.2、135.7mm;而层状土柱灌水量为170.7mm。结果表明,均质土壤湿润锋附近的积盐现象是由于土壤含水率较低、水分运移速度慢,对盐分的携带能力低而导致的;盐分将随着灌水量的增大而向土壤深层运移并被排除。层状土中的黏土夹层对盐分运移具有明显的阻滞作用,使盐分在黏土层中大幅增加。土层之间的渗透性差异越大,黏土夹层的滞盐作用越强。除此以外,黏土夹层具有拟半透膜作用,使水分比盐分更容易穿过黏土夹层,增加夹层下部土壤含水率。

Based on the soil columns with different layered soil structure, the infiltration experiments were conducted to research the retardation effect of layered soil with clay interlayer to the salt transfer under drip irrigation, and the experimental results were compared with those on the homogeneous soil columns. The loose sand and light loam were used in homogeneous soil columns, and loose sand with light clay in- terlayer （LSLCI） as well as light loam with light clay interlayer （LLLCI） were used in layered structural soil columns. The experiments were designed to irrigate homogeneous soil columns with water of 88. 5 mm, 106.2 mm and 135.7 mm and layered soil columns with water of 170.7 mm. The results showed that the salt accumulated near the wetting front in homogeneous soil resulted from the low soil moisture content and slow soil water transport speed which led to low salinity carrying capacity, but the salt would trans- ferred into deep soil and then was drained out of soil with the increase of irrigation water. The clay inter- layer had an obvious retardation effect on salt movement which made the salinity increased significantly in the clay layer. And the greater differences of the permeability between soil layers caused much retardation effect to salt transfer. In addition, the clay interlayer had a quasi-semipermeability, which made the water transport through the clay interlayer easier than the salt, and the soil moisture content under the interlayer was increased.