金沙江下游季节性干旱区紫色土坡耕地土壤水分变化特征

Moisture Characteristics of Purple Soil in a Seasonal Arid Area in the Lower Reaches of the Jinsha River

土壤水分是季节性干旱区农业生产的限制因子,研究紫色土坡耕地土壤水分变化特征有助于解决坡耕地的生态水文型干旱问题。以金沙江下游季节性干旱区紫色土坡耕地为研究对象,使用PR2/6土壤剖面水分测定仪在雨季对5°、10°、15°、20°、25°、30°坡面10、20、30、40、60、100 cm土层的土壤体积含水量进行连续监测,分析紫色土剖面含水量变化特征。结果表明:坡耕地土壤水分随时间的变化特征可分为四个阶段:6月初至6月底为土壤水分恢复期,7月初至8月中旬为土壤水分快速补充期,8月中旬至8月底为土壤水分消耗期,9月初至9月底为土壤水分回升期。土体剖面含水量自上而下呈现逐渐增加的趋势,且各层含水量都具有显著的差异性和相关性。6个监测点最大含水量均出现在100 cm处,为19.67%~33.82%,最小含水量大多出现在20 cm处,为3.07%~11.71%。土壤含水量变异系数自上而下逐渐降低,10 cm处土壤含水量变异系数最大,为8.67%~56.28%,100 cm处最小,为0.68%~14.76%;土壤含水量随着坡度的增加总体上呈减小趋势,在0~60 cm土层,10°监测点的土壤含水量最高,为12.20%~20.40%,在0~100 cm土层,25°监测点的土壤含水量较低,为4.28%~19.22%。降雨和坡度对土壤含水量均有显著影响,二者对土壤含水量的影响随土层深度的增加而减弱。研究结果对紫色土坡面水资源高效利用及提高农业生产力具有重要意义。

Soil water is the limiting factor for agricultural production in seasonal arid area,so the study of moisture characteristics of Purple Soil can help solve the eco-hydrological drought problem of cultivated slope land.Taking the Purple Soil of cultivated slope land in a seasonal arid area as the research object,the PR2/6 soil profile moisture analyzer was used to monitor soil moisture contents within 0-100 cm depths at 5°,10°,15°,20°,25°,30°slopes in a rainy season.The characteristics of soil moisture were investigated.The change of soil moisture content with time was divided into four stages:soil moisture recovery period(from the beginning of June to the end of June),soil moisture rapid replenishment period(from the beginning of July to the middle of August),soil moisture consumption period(from the middle of August to the end of August)and soil moisture raise period(from the beginning of September to the end of September).Soil moisture content was increased with the increase of soil depths.The soil moisture content had a significant difference and correlation among different depths.The soil moisture content in six sites all appeared the maximum at 100 cm depth with the range of 19.67%-33.82%,while the minimum mostly occurred at 20 cm depth,ranging from 3.07%to 11.71%.The coefficient of variation(C.V.)of soil moisture content decreased with the increase of soil depths.The C.V.was the largest at 10 cm depth,ranging from 8.67%to 56.28%,but was the lowest at 100 cm depth,ranging from 0.68%to 14.76%.The soil moisture content generally decreases with the increase of slope.The soil moisture contents within 0-60 cm depths were higher at the 10°slope than those at the other slopes,ranging from12.20%to 20.40%;the soil moisture contents within 0-100 cm depth were relatively low at 25°slope,ranging from4.28%to 19.22%.Both rainfall and slope have significant influence on soil moisture content.With the increase of soil depth,the influence of both rainfall and slope on soil moisture content decreased.These results were of great significance for the efficient use of water resources and the improvement of agricultural productivity of cultivated slope land in seasonal arid areas.