Soil moisture dynamics in sowings of grain-fallow-cutting crop rotations in the Northern Steppe of Ukraine

Moisture content is one of the most important conditions of plants life. The productivity of field crops is directly proportional to their moisture content. With enough soil moisture, favorable conditions are created for the growth and development of field crops, and eventually their yield increases. There is situation, that not formed a permeable, least saturated soil moisture class, in the conditions of the Northern Steppe of Ukraine, regardless of the methods and systems of soil cultivation. That is, it was not typical for the annual wetting of one and a half meter of soil, which was characterized by a lack of normative amount of precipitation during December–February, the absence of snow cover with increased wind activity. Precipitation water humidifies the soil only by 90–110 cm to the level of HM (the highest moisture content), resulting in a dry layer between the accumulated moisture during the cold period and the moisture in the deep layers of soil at the level of PM (persistent moisture). During spring-summer vegetation of plants, the root system, reaching the dry layer (PM), in most cases cannot reach deeper layers; with the plants begin to suffer from drought, especially in the absence of rainfall during the growing season, reducing the yield. Total soil moisture costs varied within a narrow range (306.2–310.4 mm) and remained almost unchanged depending on the tillage systems. Economical water consumption by field crops is characteristic of a shallow mulching system of soil cultivation, as evidenced by the decrease of the index of water consumption by 13.4 mm/t compared to the board system. The advantage of the board system of cultivation of soil in the additional accumulation of moisture during the autumn-winter period is noted in the years with frosty snowy winters, slow and prolonged snowmelt, shallow mulch flat-cut loosening – in case of shortage of the normative amount of rainfall during December – February, lack of snow cover and increased wind activity. The use of preserving (chisel) cultivation under a differentiated system increases the moisture accumulation by 91.0–179.0 m³/ha in the autumn-winter period due to plant residues that delay more snow, especially in the warm snow-less winters. The use of a shallow mulching system of soil cultivation, despite the decrease in grain yield, contributes to a more economical consumption of moisture per unit of crop by 1.1‒1.2 times during the growing of field crops.