Available Moisture Storage Capacity in Relation to Textural Composition and Organic Matter Content of Several Missouri Soils

Abstract

Analaysis of the available moisture storage data for 271 profile horizon samples from soils of northwestern, central, eastern, and southwestern Missouri show that for these dominantly silty soils available moisture storage capacity (A.W.C.) decreases with clay and increases with silt content. Coarse silt (0.05 to 0.02 mm.) increases A.W.C. more than fine silt (0.02 to 0.002 mm.). A.W.C. also increases generally with organic matter content but since organic matter increases with coarse silt and decreases with clay the effect can be attributed to textural changes. The siltrich surface is higher in organic matter and A.W.C. than the clay-rich subsoil (particularly the clay pans). Only in a grouping of samples between 13 and 20% clay is there evidence that organic matter may improve storage, possibly by forming silt sized microaggregates in the clay. This effect is not apparent in soils dominated by fine textural components and relatively low in organic matter.