Transformations of native and applied potassium under wheat-maize cropping sequence in mid hill soils of Himachal Pradesh

Native available and non-exchangeable K in untreated soils decreased by 2.14 and 0.43% ofthe initial content after harvesting second crop of wheat. The respective figures for second maize crop were higher viz. 4.27 and 2.31%. The data regarding concentration of different forms, uptake and fixation of K, as a function of applied K, under two cropping systems showed substantial increase in all the three parameters with increasing amount of added K. At 100, 200 and 300 Kg/ha levels of application, available K increased by 3.8,6.4, 12.6% and 4.3, 5.0, 5.8% over control after the harvest of second wheat and maize crop, respectively. Respective figures for non-exchangeable K were 7.1, 15.3,22.4% and 5.1, 10.6, 18.5%. Mean increase in K uptake by wheat crop was recorded to be 107, 111 and 152% over control at three levels of K application in order, while that in case of maize crop was 118,231 and 251%. About 78,86 and 85% of the added K at 100, 200 and 300 Kg/ha levels of application got fixed as non-exchangeable K under wheat cropping system which dropped to respective 23, 47 and 61% under maize cropping system. Rate of K release declined with increase in slope and followed the order: Ferromagnesian shales and dolomitic lime stone > ferromagnesian shales and dolomite> ferromagnesian shales and sandstone, with respect to type of parent material.