A NEW LABORATORY METHOD TO QUICKLY DETERMINE THE UNSATURATED HYDRAULIC CONDUCTIVITY OF UNDISTURBED SOIL CORES WITHIN A WIDE-RANGE OF TEXTURES

A modified instantaneous profile method is described, which determines the hydraulic conductivity functions of soils with varying textures. Soil suction head as a function of time and depth, rate of outflow as a function of time and the final distribution of moisture content are monitored on undisturbed soil columns. Data is handled following a modification of the procedure of Weeks and Richards (1967). The apparatus consists of five measuring cells, a monitoring unit, five balances and equipment to section the soil columns for the gravimetric determination of soil moisture content. Each measuring cell contains a soil core of 250 cm3, into which five micro‐tensiometers are inserted at 2 cm intervals. Exemplary hydraulic conductivity functions are shown for samples taken from an Arenosol, from silty and clayey‐silty horizons of a Luvisol and from a clayey Vertisol. The functions showed good agreement with in situ data. Evaluations of variability show the method to be very reliable. On average, the functions of five samples can be determined in one week, making the method quick. At the same time, the method has great potential for the study of effects of soil structure on hydraulic conductivity. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim