The influence of the moisture content,texture and organic matter on the aggregation of sandy and loamy soils

It is generally accepted that water is one of the major factors involved in the aggregation process. This is proved by the change in bulk density of a soil wetted to different water contents and submitted to a certain number of standardized knocks.The water content corresponding to a minimal bulk density, resulting in an optimal aggregation, is called optimal or critical moisture content. The corresponding suction or critical capillary depression is inversely proportional to the particle size and thus will increase as the latter decreases. The pF-value at the critical moisture content ranges between 2.30 for sand and 3.32 for sandy loam.Organic matter also plays an important role in the aggregation process, but has no influence on the critical capillary depression. From a quantitative point of view the organic matter is a better aggregation agent than clay and silt.