TOWARDS THE HARDENING OF SANDY SOILS - A NATURAL EVOLUTION IN SEMIARID TROPICS

In semi-arid tropics, the desertification results frequently from the degradation of the physical properties of the soils. For sandy soils, usually friable and permeable, this degradation which consists of the development of hardness and low permeability, was related to the groun dmass fabric. Even at low content, the fine clay formed wall-shaped br idges between the skeleton grains and caused a high continuity of the solid phase. This fabric resulted from natural evolution closely relat ed with water dynamics and favoured by lithology and climate. Without necessarily human intervention the supergeneous materials lost their c haracteristics of being loose, hydrated and biotic.