Volume Change in a Swelling Clay and Its Influence on Soil-Moisture Relations

The bulk-density and associated moisture content of clods collected from 0–10, 50–60, 100–110 and 150–160 cm layers of a wet clay-soil profile were determined and statistically correlated in the 0.05–0.25 g/g moisture content range. The bulk-density at all depths decreased linearly with increase in moisture content, and increased with depth through 100 cm profile at a particular moisture content. Analysis of the moisture content-volume change data revealed a significant effect of overburden on soil-moisture potential and suggested estimation of overburden potential for inferring matric potential from in situ measurements of soil-moisture potential in the wet range. The matric potential at respective moisture contents thus inferred should be used rather than in situ measured moisture retention curve to characterize field profile of a predominantly swelling clay.