Retention and Release of Soil Water as Related to Mineralogy of the Soil Clays

Retention and release of water were maximum in bentontte (clay) folhwed by illite and kaolinite. With rise in matric suction, the difference in the retention by these clay minerals narrowed down. At 10 centibar, bentonite retained 244 per cent more water than kaolinite, whereas at 15 bar, it was merely 9 per cent. The black soils, being very fine textured and having montmorillonite as the dominant clay mineral, retained and released the largest amount of water, followed, in general, by the alluvial (illitic) and laterltic (kaolinitic) soils. Moreover, the water retention curves of the black, alluvial, red and lateritic soils resemble those of bentonite, illite, and kaolinite respectively. Both the nature and amount of the clays are important factors in determining the water retention characteristics of soils.