旱地覆膜保墒问题的观测

Experience of Water Conservation with Film Mulching in Dry Land

根据地膜覆盖中发现的异常问题,对旱地覆膜保墒进行了试验,结果表明,地膜保墒既要有充足的水分贮备,又要有及时的水分补充,地膜对土壤中水分的蒸发既有隔阻,又有加速水分蒸发的作用,隔阻作用随着土壤中气温的升高和水分的降低而减弱,蒸发作用随着气温的升高而加剧,使地膜下土壤出现提前干旱。地膜对土壤接收雨水有阻挡作用,不利于雨水为旱地增墒;在长期覆膜的情况下,地膜下的土壤,在地表1 cm表现湿润从而造成地膜能提墒的假象,在1 cm以下的含水量低于露地;要使地膜对旱地确有保墒作用,应在雨前启膜,雨后盖膜,但操作性甚差。

In terms of the abnormal soil water phenomena under plastic mulching, an experiment was conducted. The result shows that under plastic film mulching, there must be enough stored water and additional water. The plastic film not only hinder evaporation, but also accelerate evaporation. When soil temperature is rising and water content is descending, the hindering will weaken. Soil temperature is higher, evaporation is more severe. Soil, covered with film for a long time , looks like having enough water because surface layer I cm is wet. In fact, the soil water content under 1 cm is lower than that of outside. To save soil water under film, the film should be uncovered before rain and recovered after rain, but it is hard to do.