Non-exchangeable potassium release and supplying power of soils of Haryana, Northwest India

The management of potassium (K) necessitates the understanding of K dynamics and assessment of crop-available K reserves. Non-exchangeable K (NeK) could have a substantial impact on plant nutrition, therefore, non-exchangeable potassium release and supplying power of soils from four different soil orders of Haryana, Northwest India was examined. After successive cropping with maize and oats, initial exchangeable K contents of 0.38, 0.22, 0.25 and 0.09 cmol(p(+)) kg(-1) declined by 23.37%, 27.28%, 29.41% and 27.77% in Alfisols, Inceptisols, Entisols and Aridisols, respectively. The release of non-exchangeable K to plant roots in screen house was compared with K release to nitric, citric and oxalic acids in the laboratory to assess the feasibility of these acids for non-exchangeable K extraction. The amount of K released was quantified as cumulative uptake by maize and oats. Non-exchangeable K released to plant roots (r = 0.94; p <= 0.01) and oxalic acid (r = 0.63; p <= 0.05) were significantly correlated with cumulative K uptake. The initial level of exchangeable K (Ex-K) and cumulative K uptake by maize and oats exhibited strong and significant correlation (r = 0.85; p <= 0.05) signifying that K removal by crops results in the equilibrium among different K pools. The strongly significant relationship between non-exchangeable K released to oxalic acid and plant roots (r = 0.92; p <= 0.01) affirms the reliability of laboratory methods vis-a-vis K release studies.