Phosphate sorption in benchmark Vertisol and Alfisol profiles.

The response of crops to added P is generally less predictable on Vertisols than on other soils such as Alfisols under similar agroclimatic conditions. The cause of low P responses to applied P in Vertisols is not known but is often attributed to sorption of phosphate (Murthy 1988). However, recent work on the behaviour of P in Indian Vertisols indicate that the Vertisol