Soil Cohesion as Affected by Freezing, Water Content, Time and Tillage

This study was developed to determine whether there are substantial annual changes in soil cohesion and to identify major factors causing those changes. Aggregate stability was measured throughout the year on soils in Utah and Idaho using wet sieving techniques. Stability generally increased during spring and summer months. Major decreases of cohesion, found when minimum daily air temperatures fell to or below 0 °C during winter and early spring months, were attributed to pressures and associated shearing forces caused by freezing at high water contents. Equivalent disruption occurred when confined soils were frozen in controlled laboratory studies. Disruption also increased as water content at the time of freezing increased for all soils studied. Disruption of soil by rototilling and compaction significantly decreased soil cohesion.