Soil Water Hysteresis in Silt Loam and Clay Loam Soils

The microhydrologic properties involving water content, pressure head, and hydraulic conductivity were measured simultaneously for a silt loam and for a clay loam soil. Large hysteresis in the water content-pressure head relationship was found for both soils, the silt loam soil showing the larger amount. There was no measurable hysteresis in the relationship between hydraulic conductivity and water content in either soil. The data from the clay loam soil showed considerable scatter attributed to structural rearrangement in the soil during measurement. A formulation of the independent domain theory by Everett was unsatisfactory for predicting the observed scanning curves in the water content-pressure head relationships of both soils. A theorem of an alternative formulation by Enderby was tested by comparing differences in slopes for reversals from drying to wetting along the main curves to those found on a scanning curve; Enderby's formulation was probably no better for the silt loam soil under the conditions of test than that of Everett.