黄土高原不同类型旱区旱作粮田深层土壤干燥化特征

随降水量趋势性减少和粮食产量不断提高，黄土高原旱作粮田深层土壤干燥化现象日益显现。在黄土高原不同类型旱区，测定了32类旱作粮田0～600cm土层土壤湿度，分析和比较了各类粮田深层土壤贮水量、土壤湿度剖面分布和土壤干燥化强度。结果表明：①32类旱作粮田0～600cm土层土壤湿度、土壤贮水量和土壤有效贮水量分别为13.90%、1084.4mm和573.7mm，其中有16类粮田发生了土壤干燥化现象，土壤水分过耗量平均值85.1mm；②有28类旱作粮田100～400cm土层为土壤干层，其中夏粮田土壤干层厚度大于秋粮田，最大耗水深度接近或超过600cm；③32类旱作粮田和16类干燥化粮田土壤干燥化指数分别为110%和83%，分别属于无干燥化和轻度干燥化强度，土壤干层厚度平均值为267cm，以半干旱偏旱区粮田土壤干燥化程度最严重。

Characteristics of Deep Soil Desiccation on Rainfed Grain Croplands in Different Rainfall Areas of the Loess Plateau of China

With rainfall decreasing trendily and grain yield increasing continuously, soil desiccation occurs gradually on grain croplands of the Loess Plateau. Based on extensive deep soil moisture observations of 32 kinds of rainfed grain croplands on semi-humid area, semi-arid area and semi-arid drought prone area of the Loess Plateau, the soil water amounts, soil moisture distributions and soil desiccation intensities on the grain croplands were analyzed and compared. The results are showed as following: 1) Average soil moistures, total soil water amounts and total available soil water amounts in 0-600 cm soil layers of grain croplands were 13.90%,1084.4mm and 573.7mm respectively;soil desiccations occurred on the 16 grain croplands and an average soil water overuse amount was 85.1mm. 2) The 100-400 cm soil layers on the 28 grain croplands were desiccated soil layers, soil moisture of summer grain croplands was lower than autumn grain croplands and maximum soil water use depth of grain croplands was close to or over 600cm. 3) Average soil desiccation index of the 32 grain croplands and the 16 desiccated grain croplands was 110% and 83%, respectively;soil desiccation intensity belonged to non-desiccation and slight desiccation intensity accordingly, and average thickness of desiccated soil layers on the 32 grain croplands was 267cm. Soil desiccation of grain croplands on semi-arid prone drought area was the severest one among three rainfall regions.