用毛细吸渗原理快速测量土壤田间持水量的研究

Principles and experimental verification of capillary suction method for fast measurement of field capacity

田间持水量是衡量田间土壤保持水分能力的重要指标,视为对作物有效的土壤水分的上限,对农田灌溉和作物水分管理具有十分重要意义。该研究提出了能快速测量土壤田间持水量的新型毛细吸渗法。该方法以田间持水量为无地下水影响下土壤基质所能吸持的最大含水量为物理基础,设计了一套满足田间持水量要求的实验方法、装置和程序,采用5种不同土壤测量了其田间持水量,并与用威尔科克斯法测量得到的田间持水量进行了对比。结果表明:所提出的新型测量方法,无论是基本原理还是室内试验均可行。与威尔科克斯法相比,其测量值略微偏小;两种测量值相关性很好,相差约为9%,产生这种现象的原因主要是土壤的吸湿过程与脱湿过程中土壤含水率的滞后所致。与传统的测量方法相比,该方法可大大缩短测量时间,具有利用前景。

Field capacity （FC）, as the upper limit of water content in the soil profile available to plant use, is a crucial characteristic of soil water content, and is of great importance to irrigation and soil water management. A new method was advanced for fast determination of FC using soil capillary suction, based on the matric potential of soil water and the concept of FC. The foundation of the new method is based on the fact that the FC is the maximum sustained moisture content of the soil without groundwater impacts. The experimental method, device and procedures were designed to conduct a serial of laboratory experiments for FCs of five actual soils. The results show that ： 1） the newly suggested method is feasible in terms of both the principles and the experimental methods; 2） the measured FC values with the new method were a little lower than those with Welcox method by about 9%, which is mainly due to the hysteresis of soil moisture in the sorption and desorption processes; 3） the measured values with the two methods were very well linearly correlated as y = 1.09x. Compared with the conventional methods, the new method needs much shorter time to make a measurement. The new method for FC with soil capillary suction will find its wide applications.