EQUATIONS TO PREDICT MEASURES OF STRUCTURAL STABILITY AT MINIMUM STRENGTH

The objective of this study was to develop a procedure to predict the maximum potential amount of clay dispersible from soils during wetting . Information in the literature on the relationship between soil water content at sampling (THETA) and dispersible clay (DC) and that betwee n THETA and wet aggregate stability for 10 different soils was used to develop extrapolation equations. The THETA at which DC became maximum (defined THETA(max)) ranged from 0.34 to 0.54 kg kg-1, and it increas ed with increasing clay and organic matter contents (R2 = 0.56). The D C(max), defined as the amount of clay that will disperse at THETA(max) , ranged from 3.22 to 20.05 g clay 100 g-1 soil. The DC(max) increased with increasing clay and decreasing organic matter contents (R2 = 0.9 2). Decreases in organic matter content brought about larger increases in DC(max) in a clay soil than in a loam.