Kinetics of non-exchangeable potassium release in representative soils of Punjab

The non-exchangeable potassium (NEK) is the major portion of the reserve of available K in soils and primary factor in determining soil K fertility. The kinetics of NEK release in 10 different soil types of Punjab having a wide range in available K was investigated by successive extraction with 0.01M oxalic acid over a period of 200 h. The cumulative amount of NEK release ranged between 86 and 253 cmol x 10−2 K kg−1 in different soils. The highest amount of NEK release (253 cmol x 10−2 K kg−1) was recorded in loamy sand soil from Mansa district and the lowest amount (86 cmol x 10−2 K kg−1) was recorded in soil from Gurdaspur district deficient in available K. Based on high coefficient of determination (R2) and low values of standard error of estimate, kinetics of NEK release from all the soils were adequately described by Elovich, First order, power and parabolic difusion models but Elovich was found the best ftted model because of highest R2 values, while zero order model was not suitable to describe NEK release.