SPATIAL AND TEMPORAL FEATURES OF DEHUMIFICATION OF CHERNOZEMS OF THE PRYDNISTERSKA UPLAND

Abstract

Purpose. In the structure of the soil cover of the Prydnisterska upland, the area of chernozems is 4 060 km2. The overall rate of plowing up of the territory reaches 80%. The agricultural use of chernozems led to the transformation of almost all processes and properties, but these changes were most reflected in the humus state. A decrease in the intake of organic matter and an increase in its mineralization led to an active manifestation of dehumification. Therefore, the study of this problem will provide a scientific basis for effective fertility management, analyze the current state and propose measures to restore the ecological stability of chernozems at the regional level. The purpose of the research is to characterize the dynamics of the humus content in the chernozems of the Prydnisterska upland during the industrial period (from the beginning of the 20th century to the present), as well as to analyze the extent of the manifestation of dehumification of chernozems in flat and slope areas. To achieve this goal, the following were carried out: the field stage of work on the selection of soil samples, laboratory analytical studies of the humus content, analysis of data from archival materials and the results of preliminary studies on the relevant topic. The object of the research comprises typical chernozems and podzolized chernozems of the Prydnisterska upland. The subject of the study is the humus content of the arable horizon (0–20 cm) of chernozems of flat and slope relief with varying degrees of erosion. Data & Methods. The study of the problem of dehumification of chernozems of the Prydnisterska upland was carried out using generally accepted methods: comparative-geographical, comparative-analytical and comparative-profile. Archival materials of soil science expeditions, statistical data of preliminary agrochemical surveys and our own research results obtained during 2019–2020 (research sites “Savyntsi», «Ruda», «Basivka» and «Kadyivtsi») were used for a comparative analysis of the dynamics of the humus content in chernozems over the last century. Results. Analysis of the data on the humus content in the chernozems of the Prydnisterska upland during the industrial period, at different times, confirmed the active manifestation of dehumification. The intensification of agriculture in the region, neglect of soil protection technologies and insufficient application of organic fertilizers have led to the formation of a negative humus balance. For 106 years (from 1914 to 2020), the humus content of the chernozems of the Prydnisterska upland has decreased by 30–45%. The most intense losses of the organic component have been recorded by the beginning of the 90s of the 20th century. The total loss of humus by chernozems during this period amounted to 36–48 t/ha. According to the accepted estimates of the humus content, the chernozems of the study area in modern soil management conditions are characterized as low-humus with a humus content (3–4%). Statistical data indicate that the intensity of dehumification has decreased over the past 6 years, but the negative humus balance remains. Losses of humus (in the 0–20 cm layer) decreased to the level of 0.28–0.36 t/year, however, these data are correlated depending on the structure of crop rotations, soil cultivation technologies and fertilization rates. According to the results of the study, it has been found that the variability of the humus content within the arable horizon (0–20 cm) increases with a change in the morphometric parameters of the relief and the intensity of manifestation of erosional degradation. In particular, a critical situation is observed on slopes with a steepness of 5–6 °, which are distinguished by the lowest reserves of humus. Dehumification of chernozems of the Prydnisterska upland is the result of an unbalanced anthropogenic impact. Optimization of this problem requires the widespread introduction of soil protection technologies on slope areas of the relief, the introduction of an appropriate amount of organic fertilizers, sowing green manure crops, conservation of eroded areas.