全量程(多分子层到饱和)土壤持水曲线变化规律初探

Changing Regularities of Soil Water Characteristic Curves in the Whole Range From Multimolecular Layer to Saturation

通过压渗法、冰点降低法和吸湿法分别测得砂土、粉土和粘土三种土类从多分子层到饱和全量程土壤持水曲线。试验表明,土水势与土壤重量含水量(以下简称含水量)之间的关系可用指数方程表达。在含水量相同情况下,土水势绝对值随粘粒增多、含盐量增大和干容重减小而增大且与土壤水分变化过程有关,脱湿过程的土水势绝对值比吸湿过程的大。簿膜水范围内土壤持水曲线的滞后现象可用公共水化膜理论来解释。

By using the methods of water extraction, freezing point depression and moisture absorption, three types of soil (i.e., sand, silt and clay) were tested to obtain the soil water characteristic curves in the whole range from multiolecular layer to saturation. It was found that the relationship between the absolute values of the soil water potential and water content could be expressed by a power equation. The absolute value of the soil water potential increases with the increasing of the clay particle content and salinity and the decreasing of the dry density of soils as water content is the same. It is related to the changing process of soil water. The absolute values of soil water potential in the dehydration process are greater than those in the hygroscopic process. The hysteresis of the soil water characteristic curves in hygroscopic process could be explained by the theory of overlapping hydrate film.