Potash State of the Soil and Crop Productivity when Applying Mineral Fertilizers and Plant Residues

In micro-field experiments conducted on gray forest soil, changes in the forms of potassium under the influence of mineral fertilizers and plant residues were studied. It is shown that the soil potassium contained in a water-soluble and easily exchangeable form varied widely. In the conditions of 2012, when applying K60 on the background of nitrogen and phosphorus, the content of water–soluble potassium increased by about 2 times compared with the control, and the content of light-exchange potassium increased by 4 times. In the case of embedding plant residues in the soil, the potassium content in the water–soluble form increased by 2 times, light-exchange – by 2.5 times, respectively. The content of exchangeable potassium changed little in the variants, the changes affected the non-exchangeable form to a greater extent. In particular, the content of non-exchangeable potassium in 2018 decreased by 1.5–2.0 times compared to 2012, which required the creation of a more reliable basis for obtaining objective information about the state of the potash fund of the soils of the forest-steppe zone. Under the influence of K-fertilizers in combination with plant residues, plant productivity stabilized, and at the same time a positive balance of potassium in the soil was formed.