Nonexchangeable potassium release to H+-saturated resin and its diffusion characteristics in some soils of Lesser Himalayas

摘要

Kinetics of potassium (K) release from some soils and their fractions in relation to diffusion parameters was investigated by equilibrating the soils and their fractions with chloride-free H+ resin for periods of 0.25, 0.5, 1, 2, 5, 10, 25, 50, 100, and 200 h. Diffusion of applied K was estimated by employing half-cell technique. Potassium released to H+ resin after 200 h of equilibration was 0.78, 0.49, and 0.55 cmolc kg-1 for the selected soils of high-, mid-, and low-altitude zones of the Lesser Himalayas, respectively. Potassium released from silt fractions did not vary much among the three zones. Nonexchangeable K released from clay fraction at 0.77 to 1.11 cmolc kg-1 was higher in the soils of the high-altitude zone. The rate of nonexchangeable K release was faster for first 5 h of reaction period, and thereafter, it leveled off with time. The value of diffusion coefficients ranged between 8.01x10-8 to 4.33x10-7 cm2 sec-1 in these soils. The diffusion coefficients were large where the exchangeable K contents in soils were higher..