Determination of soil sorptivity and hydraulic conductivity from the disk infiltrometer

A simple two-term infiltration equation was used to determine soil sorptivity and hydraulic conductivity from cumulative infiltration data from the disk infiltrometer. Parameters of the equation were obtained bg fitting the equation to cumulative infiltration data. The parameters of the first and second terms in the equation were related to soil sorptivity and hydraulic conductivity, respectively. By using the two-term infiltration equation, sorptivity and hydraulic conductivity were estimated for various soils, radii and tensions of the disk infiltrometer, and initial infiltration conditions. Sorptivity and hydraulic conductivity values calculated using the method and simulated cumulative infiltration data resulted in excellent agreement with the theoretical results. The relative error of estimation of sorptivity and hydraulic conductivity was within 5% for most cases. The method can be used to determine the soil hydraulic properties from infiltrometer infiltration for a wide range of soils, having a retention function of the type of either van Genuchten, Russo, or Zhang and van Genuchten.