Comparison of potassium sorption characteristics of cultivated and virgin soils in Khoy region

The present study was conducted to study of potassium sorption behavior of soil in Khoy region. Sorption isotherm was constructed in the laboratory by equilibrating and shaking 2.5 g soil with 25 ml of 0.01 mM CaCl2 containing 0-150 mg K L-1 as KCl for 24 h. After equilibrium, remaining concentration of potassium measured and potassium Quantity-Intensity (Q/I) curves and their parameters such as potassium buffering capacity (PBCK¡( potassium activity ratio at equilibrium (AReK), readily exchangeable K (∆K0), standard potassium requirement (SKR), equilibrium potassium concentration (EKC) and energy of exchange (EK) were calculated. Mean comparison of paired soil samples indicated that the AReK, EKC and ∆K0 values of cultivated soils were significantly (p≤0.001) lower than those of virgin soils, indicating decreasing of potassium in the cultivated soils. As with cultivation, AReK mean decreased from 0.0188 to 0.0048 (mol.L-1)0.5 and ∆K0 mean decreased from 0.117 to 0.057 cmolc kg-1. Mean of equilibrium potassium concentration (EKC) in virgin and cultivated soils was 91 and 34 mg.l-1 respectively and PBC mean for cultivated and virgin soils measured 11.8 and 7.7 cmolc.kg-1/(mol.L-1)0.5 respectively. It was concluded that soils of studied region have relatively sufficient potassium for plants but cultivation and fertilizer management lead to a reduction in the amount of potassium in soils and increasing the adsorption parameters.