Potassium release to proton saturated resin and its diffusion characteristics in some alluvial soils

Kinetics of K release from soils and their different size fractions in relation to diffusion parameters was investigated by equilibrating with chloride free H-resin for time periods, up to 100 h. Diffusion of applied K was investigated by employing half-cell technique. Potassium released to H-resin after 100 h equilibration was 0.45 to 0.59 for submontane (mean annual rainfall > 800 mm), 0.50 to 0.58 for central plain zone (mean annual rainfall 400 to 800 mm) and 0.60 to 0.67 cmol kg− 1 for southwestern zone (mean annual rainfall < 400 mm) of the upper Indo-Gangetic plain. Potassium released from silt fraction did not vary much. Non-exchangeable K released from clay fraction at 0.86 to 1.16 cmol kg− 1 was higher in southwestern zone. The rate of non-exchangeable K release was faster for first 5 h of reaction period and thereafter it leveled off with time. The values of diffusion coefficients of soil K ranged between 2.6 × 10− 22 to 282.5 × 10− 22 m2 s− 1 in these soils. The diffusion coefficients were large where the exchangeable K contents in soil were higher. Silt fraction of these soils showed relatively higher values of diffusion coefficients.