Determination of sorptivity, infiltration rate and hydraulic conductivity of soil using a tension infiltrometer

This study was conducted in June-July 2018 to determine hydraulic properties of soil mainly: sorptivity (S); infiltration rate (I); hydraulic conductivity (K) and water diffusivity (D) using a tension infiltrometer. These soil properties are required during the design of irrigation and drainage projects. The Experimental site was the Demonstration Farm of Department of Agricultural and Biosystems Engineering (DFDABE), University of Ilorin, Ilorin, Nigeria. The soil was loamy sand with mean porosity of 42.90%, percentage contents of sand, silt and clay were 84.35, 5.41 and 10.24%, respectively. A tension infiltrometer which restricts preferential flow of water in the soil was used to measure the infiltration rates. Water potentials of -0.02, -0.05, -10 and -0.15 m were used but -0.05 m was found to be most appropriate for tension infiltrometer. Potential -0.02 m could not control preferential flow of water during infiltration test. The infiltration data were used to determine S, I, K and D of the soil. The mean values of S, I, K and D at -0.02 m in 2018 were 63.50 mm/h1/2, 176.84 mm/h, 22.42 mm/h and 171,092.46 mm2/h, respectively. The corresponding values at -0.05 m were 29.90 mm/h1/2, 71.32 mm/h, 24.67 mm/h and 72,871.29 mm2/h. Corresponding values at -0.10 m were 19.88 mm/h1/2, 32.76 mm/h, 13.02 mm/h and 26,309.80 mm2/h and at -0.15 m were 15.41 mm/h1/2, 28.54 mm/h, 15.02 mm/h and 23,041.13 mm2/h. The values of infiltration rates and hydraulic conductivities of the soil can be used for design of an irrigation project in the study area.Keywords: Hydraulic conductivity, infiltration rate, sorptivity, soil porosity, tension infiltrometer, water diffusivity