ABSTRACT
The natural vegetation is replaced by agricultural plant assemblages whose survival depends on mechanical cultivation of the soil, the application of herbicides, pesticides and fertilisers, and, in many parts of the world, the implementation of irrigation and drainage. Soil erosion is a two-phase process comprising detachment of soil particles from the soil mass and their transport down slope, down stream or down wind. A framework for understanding soil erosion in this way was provided by L.D. Meyer and W.H. Wischmeier for water erosion on a hillslope. Soil has an inherent resistance to erosion and the erosive agent must attain a critical or threshold condition for detachment to occur. The shear strength of a soil is a measure of its resistance to shear stresses exerted by gravity, moving fluids and mechanical loads. The behaviour of compressible soils on saturation and when subjected to further loading depends upon whether the water can drain from the soil.
