Extractable Potassium Compounds in the Rhizosphere of Norway Maple in Podzolic Soils

Resumo

The content of potassium was determined in the whole soil and in fractions >5, 1–5, and <1 μm in extracts of 1 M NH₄OAc, 2 M HCl, and hot 10% HCl in the (AO)EL horizon of a podzolic soil in the rhizosphere of Norway maple (Acer platanoides L.) and from the bulk soil. It was established that the content of exchangeable potassium is significantly higher in the rhizosphere with a higher amount of organic matter as compared with the bulk soil. Based on the existing gradations of supply of tree cultures with this element, the soil of the rhizosphere refers to the gradation of increased level of supply, and the bulk soil is moderately provided with potassium. In the soil of the maple rhizosphere, as compared with the bulk soil, there is more hardly hydrolysable potassium, which can be explained by the transition of the element to the acid extract from the fine and poorly crystallized mica and illite particles. It is assumed that the increased content of these minerals in the rhizosphere is due the intensification of the processes of illitization and physical disintegration of mica and illite particles occurring in coarser fractions.