Potassium adsorption characteristics of soils under long term maize-legume cropping sequence

Potassium adsorption isotherms of rainfed maize growing soils of North Kashmir were studied to visualize the adsorption behavior and factors affecting adsorption. The soils vary widely in their physico-chemical properties having lacustrine origin. Potassium adsorption isotherms were constructed by equilibrating 5 g soil samples with eight levels (0 to 200 mg K). At application rates of 1 and 200 mg of K contained in 10 ml of KCl solution per gram of soil, the adsorbed amounts of K varied from 13 to 15% and 9 to 12% of the added K with an average 13 and 11%, respectively. The adsorption data were fitted to Freundlich, Langmuir and Temkin equations. Freundlich equation explained K fixation behavior better than the either two equations as evidenced by higher coefficient of determination (0.90 to 0.99). The Freundlich parameter ‘a’ was significantly correlated with clay content (0.982), pH (0.919) and cation exchange capacity (CEC) (0.907) of soils.   Key words: Potassium adsorption, Freundlich, Langmuir, Temkin.