Desorption of Potassium and Magnesium in Gray Forest Soil

It has been established that long-term potassium deficiency in an agrocoenosis reduces the ability of gray forest soil to desorb this element into the soil solution to a much greater extent than a magnesium deficiency hampers magnesium desorption. The mobility of potassium cations is higher than that of magnesium cations regardless of the soil depletion degree with respect to these elements: 0.1–0.5 M ammonium acetate solution extracts almost the entire exchangeable potassium reserve and only 65–90% of the magnesium reserve from the soil. In the course of fractional extraction of potassium with 0.001 M ammonium acetate solution, differences between soils with different potassium reserves are recorded only in the first two or three extracts, while the potassium content becomes leveled out in subsequent extracts. The magnesium content in successive extracts decreases gradually and nearly equally in soils with different initial Mg reserves. Overall, potassium and magnesium desorption intensity and specificity adequately reflect soil fertility with respect to these elements.