Potassium release characteristics of some soils of Uttar Pradesh hills varying in altitude and their relationship with forms of soil K and clay mineralogy

Release rates of non-exchangeable potassium were determined for 15 soils occurring widely in different altitude in intensively cultivated soils of U.P. hills. For this, the method of Oliver and Diarisso [Oliver, R., Diarisso, D., 1985. Cine tique de dissolution du potassi um de divers soils per allaque a chaud a Li acide nitrique normal c.r. ATP Dynamique des cations, Bull. CIRAD Montpellier, France Section, N: 1–13.] was adopted involving successive extraction contact duration with 1 N HNO3 as an extractant on water bath at 85°C. The soil series were then grouped under three classes with respect to altitude and exchangeable K contents, namely, 1250, 1650 and 2250 m AMSL with exchangeable K group 40±5, 90±15 and 140±15 mg kg−1 soil, respectively. The cumulative K release decreased with increase in altitude and exchangeable K content and the values ranged from 473 to 527, 300 to 336 and 235 to 287 mg kg−1 soil, respectively. All values of the initial linear rapid K release part (P1) and subsequent slow K release part (P2) indicated that P1 is generally greater than P2 and the values of P1 and P2 decreased with increase in altitude. Hence, it is advisable to consider the amount of exchangeable K, non-exchangeable K content and clay mineralogy while recommending the potassium fertilizer in different altitude.