Effect of Degree of Soil Profile Disruption on Plant Growth and Soil Water Extraction

Abstract Modification of slowly permeable soil profiles has been effective in ameliorating undesirable soil conditions. Various methods and depths of modification have been studied but little attention has been given to (i) the degree of disruption necessary to accomplish satisfactory profile modification or (ii) the relative merits of topsoil‐subsoil mixing and stockpiling and returning topsoil to the surface after profile modification. We studied seven degrees of profile disruption (clod size distributions in the B22t and mixing of topsoil with that horizon) in simulated soil profiles in the greenhouse. Grain sorghum ( Sorghum bicolor ) was grown on Pullman clay loam. Disturbance of the B22t layer increased yields but once that layer was disturbed, degree of disturbance had no further effect on yield. Compared with retaining topsoil on the surface, mixing it with the B22t did not affect yields.