顶凌耙地,是我国北方地区保墒防旱的一项宝贵经验,包括耙、耱、压一系列作业。一般是在惊蛰前后,田间还有冰凌时进行。保墒作用早春,随着气温回升,土壤逐渐解冻,而冻融的水分由于冻层的阻隔,不能下渗。土壤刚刚解冻后,土粒之间比较紧密,容纳水分的孔隙减少,土表含水多面泥泞,即称“返浆”。返浆期表土含水量多,蒸发损失大。不仅如此,随着土壤的解冻,使深层土壤水分不断上移而损失。据我们连续二年观测,0—5厘米土壤含水量,3月8日比4日增加1.8%,14日又比8日增加2.5%。 At the top of the ridge, it is a valuable experience in preserving soil moisture in northern China, including a series of operations such as rakes, jacking and pressing. Generally before and after Jingzhe, the field is still ice time. Preservative effect Early spring, with the temperature rise, the soil gradually thaw, frozen and thawed water due to blocking the barrier, can not penetrate. Soil just thaw, the soil between the more closely, to reduce the porosity of the water, surface water multi-face muddy, that is, “back to pulp.” Backwash topsoil moisture content, evaporation loss. Not only that, as the soil thaw, so that deep soil moisture continue to move up and lost. According to our observations for two consecutive years, 0-5 cm soil moisture content increased by 1.8% on March 8 than that on the 4th and increased by 2.5% on the 14th.