The regularities of potassium sorption by soils in Western Transbaikalia
S.B. SOSOROVA
Institute of General and Experimental Biology, Siberian Branch, Russian Academy of Sciences, Ulan-Ude, Russia
Keywords: potassium, isotherm, Langmuir equation, Freundlich equation, coefficient
Abstract
The regularities of potassium sorption from an aqueous solution of KCl were studied using three types of soils (peat lowland, light chestnut, and alluvial turf) formed in the conditions of Western Transbaikalia and their treated analogues. Potassium sorption in soil was measured in laboratory conditions using an experiment in which soils were balanced with a solution with different initial concentrations of KCl (0,5, 1,0, 3,0 and 5,0 mmol/L) for 24 h. The resulting potassium sorption isotherms were described by the Langmuir and Freundlich equations. The parameters of these equations indicate inhomogeneities of the bonds of potassium ions with the solid phase of soils. The maximum potassium uptake by the soils under study varied within 53,2-87,8 % at the initial concentration of the introduced solution of KCl in 1 mmol/L, while the distribution coefficient (Kd) of potassium between the solid and liquid phases of the soils used in the study varied from 11,37 to 72,11 L/kg. The highest value of Kd was found for peat-lowland soil and the lowest value for alluvial turf. The patterns of changes in potassium Kd correlate with the degree of its absorption by the soil. The maximum sorption capacity of potassium by the soils under study varied in the upper humus horizons from 54,05 to 98,04 mmol/kg, and in the lower horizons from 35,71 to 100,0 mmol/kg. The values of the KL coefficient of the Langmuir equation in humus horizons were slightly less (0,272-0,668 L/mmol) than in mineral horizons (0,102-1,511 L/mmol), which indicates that potassium binds more strongly in mineral horizons. The coefficient KF of the Freundlich equation in humus horizons varied from 9,98 to 23,51 mmol/kg, and in mineral horizons 6,63-26,77 mmol/kg. It was established that the soils under study are characterized by a different sorption activity with respect to potassium and form the following decreasing series according to the level of potassium absorption: peat lowland > light chestnut > alluvial turf.
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