Potassium sorption by saline soils of Western Transbaikalia

For the first time, potassium sorption in saline soils of Western Transbaikalia was studied under static conditions and a quantitative assessment of its parameters was given. It was found that the Langmuir and Freundlich equations satisfactorily describe the adsorption of potassium by the studied soils. It was shown that the maximum sorption capacity of soils (A_max) with respect to potassium varied within 5.1–137 mM K⁺/kg, which indicated a difference in sorption sites. A relatively high sorption of K⁺ by gley and typical salt marshes was revealed. The A_max value in the humus horizons varied by 2.6 times, in the underlying horizons – by 15.6 times and was minimal in the quasi-clay salt marsh. The adsorption equilibrium constant (C_L) varied in a wide range from 0.32 to 26.8 l/mM with lower values in humus horizons, which indicated less strong binding of potassium in them. The values of the capacity coefficient of the Freundlich equation (K_F) ranged from 3.1 to 91 l/kg=mM K⁺/kg in the humus horizon, from 3.2 to 69.5 in the mineral horizon. High values of the distribution coefficient (K_d) were typical for gley salt marsh and low values for quasi-gley (4.28–184 l/kg). A relatively high value of the maximum buffer capacity in relation to potassium (MBEc) was found in the gley and typical salt marshes, and a relatively minimum value was found in quasi-gley. According to the ability to sorb potassium, the saline soils of Western Transbaikalia formed the following decreasing series (weighted average in a layer of 0–30 cm): gley salt marsh > typical salt marsh > alluvial light humus saline > salt marsh > dark salt marsh > quasi-clay salt marsh. There was no clear correlation between the parameters of potassium adsorption and some indicators of soil properties. Only a weak dependence of the absorption of potassium ions on the reaction of the soil environment and the content of physical clay was observed.