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 oc curring 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 alla que a chaud a Li acide nitrique normal c.r. ATP Dynamique des cations, Bull . CIRAD Montpellier, France Section, N: 1-13.] was adopted involving succes sive extraction contact duration with I N HNO3 as an extractant on water ba th at 85 degreesC. The soil series were then grouped under three classes wi th 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 increas e 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 (P-1) and subsequent slow K release part (P-2) indicated that P-1 is generally greater than P-2 and the values of P-1 and P-2 decreased with increase in altitude, Hence, it is advisable to consider the amount of exchangeable K, non-exchange able K content and clay mineralogy while recommending the potassium fertilizer in different al titude. (C) 2001 Elsevier Science B.V. All rights reserved.