利用TDR对土壤含水量及土壤溶液电导率的同步连续测量

Continuous Measurement of Soil Water Content and Soil Solution Electrical Conductivity by Using TDR

土壤含水量和可溶解的土壤盐分浓度的测定,对了解土壤盐分的分布及移动具有重要的意义.在内蒙古黄河流域灌溉玉米田的一个野外实验中,利用TDR对土壤含水量及土壤溶液电导率进行了同时连续测量.结果表明:在降雨量较少的时期内,当土壤水分从地下含水层向地表面移动的同时,地下水中含有的盐分也通过作物根区层向地表移动;当灌溉或有强降雨存在时,土壤表面蓄积的盐分在未能完全溶解于灌溉水及雨水之前,大量的灌溉水及降雨通过土壤内的大空隙快速渗入土壤下层;余下的水分在完全溶解了土壤表面的盐分之后,缓慢通过土壤小空隙下渗.

The movement of soluble salts in soil is directly related to the movement of soil water. Therefore, simultaneous in situ measurement of volumetric soil water content （θ） and soluble salt concentration （c） is essential to clarify the distribution and movement of salts in the soil profile. Simultaneous and continuous measurements of volumetric water content and electrical conductivity of soil solution （ECw） made by using time domain reflectometry （TDR） in irrigated cornfields in the Yellow River basin, Inner Mongolia, China, were analyzed. When soil water moves upwards from a water table to atmosphere during a period of less precipitation, the soluble salts in the groundwater are transported through the root zone up to the soil surface. When basin irrigation is performed or a heavy rain occurs, part of the water flows down quickly through the macro pores before much of the salt accumulated at the surface being dissolved in it. On the other hand, the rest of water, in which the accumulated salt is fully dissolved, moves slowly through the small pores. When a large amount of water arrive the surface, soluble salts in small pores moves downwards quickly for a short distance and stays at some lower depths.