Kinetics of Nonexchangeable Potassium Release from Two Coastal Plain Soils

Abstract

AbstractThe kinetics of nonexchangeable‐K release using H‐saturated resin were investigated on Kalmia (fine‐loamy, siliceous, thermic Typic Hapludults) and Kennansville (loamy, siliceous, thermic Arenic Hapludults) soil profiles from the Coastal Plain of Delaware. Calciumsaturated soil samples were equilibrated with H‐saturated resin from 0.5 to 960 h. Equilibrium in K release in both soil profiles was attained in about 960 h. The kinetics of K release were evaluated using the Elovich, parabolic diffusion law, first‐order diffusion, and zero‐order equations. The first‐order diffusion equation described the K‐release kinetics best as evidenced by the highest correlation coefficient (r) and the lowest value of the standard error of the estimate (SE). The parabolic diffusion law also described the data satisfactorily indicating diffusion‐controlled exchange. The zero‐order and Elovich equations did not describe the data well as shown by higher SE values than those found with the first‐order diffusion and parabolic diffusion law equations. Nonexchangeable‐K release rate coefficients (k2) ranged from 1.20 to 2.2 × 10−3 h−1 in the Kalmia soil and from 1.5 to 2.9 × 10−3 h−1 in the Kennansville soil. The magnitude of the k2 values suggested low rates of nonexchangeable‐K release from the two soils.