Potassium status of sod-podzolic loamy soils

Potassium is one of the essential plant nutrients. Despite numerous surveys, some issues related to the transformation of potassium in soils require additional study. The purpose of the research was to study the potassium transformation in sod-podzolic loamy soils and its entry into plants influenced by various farming methods in long-term field experiments of different duration. Field experiments were conducted at the experimental station of the FSBSI “Pryanishnikov Institute of Agrochemistry” located in the Moscow region, Domodedovo district, village of Barybino. To study the potassium status, an archive of soil samples created in the Geographical Network of Experiments with Fertilizers was used. Soil samples were collected in long-term field experiments after their closure (experiment SH-8, year of laying – 1971–1973, duration – 14 years) or modification (experiment SH-5, year of laying – 1964-1966, duration – 28 years). The experimental schemes included the systematic introduction of various fertilizing systems (organic, mineral, organo-mineral) and the determination of their impact on crop rotation productivity and soil fertility. Previous studies have shown that the formation of the crop yield in the context of long-term potassium deficiency burdened by the absence of fertilization was chiefly due to the consumption of non-exchangeable potassium by plants. For the 14–year period, the annual use of non-exchangeable potassium in the control and NP variants was 62.0-63.0 kg K2O/ha. As potassium reserves in the soil of the control variant become depleted (longer experiment), its assimilation from the non-exchangeable form decreased by 1.6 times and amounted to 39.5 kg K2O/ha. The use of a mineral fertilizing system (potassium dose < 90 kg/ha for 14 years) increased the annual mobilization of the non-exchangeable form of the element (over 100 kg/ha of K2O). The transformation of soil potassium forms that differed in the degree of their availability for plants was determined by the fertilizing systems, the doses of potassium fertilizers in the systems, as well as the duration of the experiments.