Formation of spring reserves of soil moisture in the 10-field crop rotation of the Central Forest-Steppe

Abstract

Goal. To establish the regularities of accumulation of spring moisture reserves of atmospheric precipitation of the cold period of the year in the meter thickness of chornozem of the 10-field grain-rowing crop rotation in the long-term measurement (49 years) in conditions of unstable moistening of the central part of the Left-Bank Forest-Steppe of Ukraine. Methods. Field (for sampling in the meter thickness of chornozem in different periods), laboratory (for thermo-weight determination of humidity with subsequent calculation of its reserves for the research period), the mathematical, statistical, and comparative calculation (for the substantiation of the reliability of the obtained moisture reserve in the meter thickness and development of the statistical models of relationships). Results. For the 1975 –1988 and 2020–2024 periods, the rainfall in the cold season (XI–III) exceeded the average annual reserves by 64 mm, as in general for the 2010–2024 years. At the same time, the percentage of precipitation for the cold period of the year from the amount of annual precipitation increased from 35 (1975–1984) to 44% (2020–2024), and the amount of precipitation for the warm period of the year decreased from 65 to 57% per these periods, which was 35–40 mm less than the long-term average. In the 1975–1988 and 2020–2024 periods, in the spring there was a decrease in productive moisture reserves (by 24–37 mm) in the meter thickness of chornozem, so the moisture index decreased by 1.15–1.31 times compared to this value in the spring period of observations. At the same time, humidification conditions ranged from wet and excessively wet (η= 1.1–1.3 and = 1.3) to slightly dry (η = 0.9–1.1 and η= 0.7–0.9). Clustering of observation periods for agroclimatic parameters, productive moisture reserves and moisture index in the meter thickness of chornozem in the spring period made it possible to establish the level of remoteness of research periods and showed an increase in remoteness in 2010–2014, 2015–2019, and 2020–2024 periods as compared to the initial research period of 1975–1999, which indicated an increase in aridity of humidification conditions in the spring period of the 10 year crop rotation. Conclusions. From 2000 to 2024, with the increase in aridity of soil conditions in terms of moisture and the decrease in moisture reserves by 24–37 mm in a meter layer of soil in the spring, the productivity of a 10-degree crop rotation by grain yield was 2.25 tons/ha higher (5.3 times) than the yield when manure was applied against the background of mineral nutrition.