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通过对2009年膜下滴灌土壤水盐运移的试验研究,结果表明:膜下滴灌条件下土壤水分的再分布决定了土壤盐分的分布特征,土壤平均含水率在棉花全生育期内呈现逐渐上升的趋势。在棉花生长阶段,随着灌水量的增加,土壤盐分峰值位置呈现下移的趋势。当灌水量从3000m3/hm2增加到4800m3/hm2时,盐分峰值位置向垂直方向从35cm下移至65cm。滴灌结束之后,土壤盐分峰值的下移顺序为:处理Ⅳ>处理Ⅲ>处理Ⅱ>处理Ⅰ,这表明灌水量的增加有利于土壤的脱盐。在时间尺度上,灌溉结束时,随着时间的推移,土壤盐分呈现从深层到地表和从膜下到膜间的双向迁移趋势。在土壤盐分平衡方面,随着灌水量的增加,棉花根层(0～40cm)土壤发生脱盐,其脱盐率分别为2.5%,7.7%,9.7%和15.8%。与0～40cm土层的盐分分布相比,在0～100cm土层中,4种灌水量处理下土壤平均含盐量反而呈增加的趋势,处理Ⅰ,Ⅱ,Ⅲ,Ⅳ的土壤水电导率分别增加了0.4dS/m,0.3dS/m,0.3dS/m和0.1dS/m,积盐率分别为9.3%,6.8%,6.7%和2.6%。说明棉花在其整个生育期内,尽管膜下滴灌对浅层(根层)土壤有脱盐作用,但对于0～100cm的土层仍有积盐作用。因此,在干旱区粉砂壤土中淋洗土壤盐分较适宜的滴灌水量为4800m3/hm2。
The results showed that the distribution of soil salinity under the condition of drip irrigation under plastic film determines the distribution of soil salinity, and the average soil water content shows a gradual increase during the whole growth period of cotton the trend of. In the cotton growing stage, the peak position of soil salinity showed a downward trend with the increase of irrigation amount. When the irrigation volume increased from 3000m3 / hm2 to 4800m3 / hm2, the peak position of salt moved vertically from 35cm to 65cm. After drip irrigation, the descending order of soil salinity peak was as follows: treatment Ⅳ> treatment Ⅲ> treatment Ⅱ> treatment Ⅰ, which indicated that the increase of irrigation amount was favorable to soil desalination. On the time scale, with the passage of time at the end of irrigation, soil salinity exhibits a two-way migration from deep to the surface and from below the membrane to the membrane. In the aspect of soil salt balance, desalination of cotton root layer (0 ~ 40cm) occurred with the increase of irrigation amount, and the desalination rates were 2.5%, 7.7%, 9.7% and 15.8% respectively. Compared with the salt distribution in 0 ~ 40cm soil layer, the average salt content of soil in 0 ~ 100cm soil layer increased with the increase of 4 irrigation treatments, and the soil water conductivity of treatments Ⅰ, Ⅱ, Ⅲ, Ⅳ 0.4dS / m, 0.3dS / m, 0.3dS / m and 0.1dS / m respectively, and the salt accumulation rates were 9.3%, 6.8%, 6.7% and 2.6% respectively. It shows that during the whole growth period of cotton, though the drip irrigation under the film has desalination effect on the shallow (root) soil, there is still salt accumulation in the soil layer of 0 ~ 100 cm. Therefore, the most appropriate amount of drip irrigation water for leaching soil salt in arid area of silty loam soil is 4800m3 / hm2.