Nonexchangeable K release and supplying power of Indo-Gangetic alluvial soils

Nonexchangeable K release in facilitating its uptake from 12 alluvial soils of three distinct agroecozones of northwestern Indo-gangetic plain has been investigated. The initial exchangeable K contents of 53, 39 and 261 mg/kg, declined by 32%, 43% and 19% in soils of submontane, central plain and southwestern arid zone, respectively, after cropping successively with maize, wheat and guinea grass. We studied the nonexchangeable K release to plant roots in green house and to H+-resin in laboratory. Release of K was quantitatively recovered as cumulative uptake by maize, wheat and guinea grass. Cumulative K uptake was significantly related to nonexchangeable K released to plant roots (r=0.85) and K released to H+-resin (0.71). Relationship between initial level of exchangeable K and cumulative K uptake in maize, wheat and guinea grass on these soils was highly significant (r=98). A significant correlation between nonexchangeable K released to H+-resin and plant roots (r=0.92) provides a commendable evidence for reliability of laboratory method for use in K release studies.