Comparative Analysis of Extractants and Temperature on Desorption of Non-Exchangeable Potassium under Different Land Uses of the North Western Himalayas

Abstract

For a better comprehension of ecosystem sustainability, the assessment of every contributory factor is of paramount significance. The non-exchangeable potassium desorption was examined in the respective samples of all the soils at three separate incubation temperatures, viz. 20, 30, and 40°C, making use of two distinct organic acids: 0.01 M oxalic acid and 0.01 M citric acid under different land uses of the temperate lesser Himalayas. The appraisal of various physico-chemical properties revealed a textural class of Sandy Clay Loam to Clay Loam under the examined land uses. The soil reaction was neutral to slightly alkaline with a pH range of 6.60–7.57. A maximum pH of 7.57 was marked in the wasteland soil and the lowest value was observed in pasture soil. A fairly high content of organic carbon (OC) was noticed, with a range of 0.46–2.03% under different land uses. Higher amounts of non-exchangeable potassium (K+) were noted to be released through oxalic acid as an extractant, followed by citric acid. The amount of non-exchangeable K+ desorbed at three different temperatures differed significantly, with maximum desorption at 40°C followed by 30°C and least at 20°C. Regardless of the temperature of incubation and extractant evaluated, non-exchangeable K+ desorption amounts were marked to be maximum under agricultural irrigated soils, and lowest was noticed from pasture soils. The Elovich equation/model was marked to be best for both treated and untreated soils under different land uses at different temperatures and extractants among different kinetic models evaluated, followed by the power function and parabolic diffusion law as elucidated by the highest values of coefficient of determination (R2) and the least values of corresponding estimates standard error (S.E.). In describing the desorption kinetics, even though the type of kinetic model remained mostly unaffected, the values of b were observed to increase in K-treated soils, i.e., from 0.308 cmol K+ kg-1 to K-saturation (100 cmol K+ kg-1) and with an increase in temperature from 20 to 40°C, indicating a pronounced release of nonexchangeable potassium in K-treated soils at higher temperatures.