A Pragmatic Method to Estimate Plant Available Water Capacity (PAWC) of Rainfed Cracking Clay Soils (Vertisols) of Maharashtra, Central India

Abstract

Three Vertisols from Nagpur, Amravati and Akola districts were studied in detail to understand the relation between moisture and soil properties. These soils are deep and during dry periods cracks cut through the slickensides in some soils with subsoil sodicity. A significant positive correlation between available water content (AWC) and smectite content, exchangeable sodium percentage (ESP) and exchangeable magnesium percentage (EMP) indicates the nature of clay and cations in exchange site plays an important role in retaining and releasing moisture. Studies on biophysical factors on water retention and release, and cotton yield in 32 Vertisols indicate that the determination of AWC and PAWC at 33 and 1500 kPa overestimates the soil moisture content because in field conditions soil water in the subsoil do not reach the saturation at 33kPa due to low to very low saturated hydraulic conductivity. A significant positive correlation between PAWC (estimated at 100-1500 kPa for non-sodic and 300-1500 kPa for sodic soils), and yield of cotton indicates that the PAWC estimated by this method can be considered as an important biophysical parameter for evaluation of rain fed Vertisols for growing deep rooted crops in Indian states in general and Vidarbha region of Maharashtra state in particular.