Scientific novelty of the research. For the first time: some agroecological indicators of typical chernozem fertility under sunflower crops, which occupied 20, 40, and 60 % of the crop rotation area, were studied, in particular, pH, electrophysical parameters, and the content of water-soluble salts of calcium, sodium, and potassium cations in the soil were determined; sunflower plant samples (baskets, stems and roots) were examined for the content of nutrients depending on the saturation of crop rotations; it has been proven that sunflower with a share of up to 40 % in the crop rotation does not lead to a deterioration in the soil's nutrient regime; it was found that when the crop rotation is saturated with sunflower by 60 %, intensive activity of cellulose-degrading microorganisms in the soil occurs; calculations were made of the economic and energy efficiency of crop rotations with a saturation of 20, 40 and 60 %.
The research to substantiate the feasibility of increasing the share of sunflower in short rotation crop rotations was further developed.
The aim of the study is to assess the agroecological state of the soil when growing sunflower with different saturation in short-term crop rotations in the conditions of the Left-Bank Forest-Steppe of Ukraine.
To achieve this goal, the following tasks were envisaged: analyse the direction of changes in soil fertility indicators depending on the share of sunflower in the crop rotation; to determine water-physical, agrophysical, electrophysical, and agrochemical soil parameters at different saturation of crop rotations with sunflower; calculate the level of water consumption of sunflower in different crop rotations; to study the microbiological activity of the soil in sunflower crops depending on the period of its return to its original place; to determine the impact of the sunflower share on its yield and productivity; to evaluate the economic and energy efficiency of sunflower cultivation with different saturation of crop rotations.
The dissertation work was carried out within the framework of the initiative topics of the Chair of Farming and Herbology named after A. M. Mozeiko: "Development of landscape-adaptive bases of modern farming systems of the left-bank Forest-Steppe and Northern Steppe" (state registration number 0117U002512), "To develop theoretical foundations of soil protection system of agriculture in the Left-Bank Forest-Steppe and Northern Steppe of Ukraine" (state registration number 0121U108245), CCI with AGROZOVET Science Park LLC (SRW № 05/21/D). We also received a grant for «Influence of saturation of short-term crop rotation with sunflower on soil moisture» within the framework of the project of the Czech Republic «Interuniversity cooperation as a tool for enhancement of quality of selected universities in Ukraine» 2019–2021.
To solve these problems, five-field crop rotations were studied, in the structure of which the share of sunflower was 20, 40 and 60 %. To determine the effect of sunflower crop rotation saturation on the fertility of typical chernozem, the following agroecological indicators were studied: water-physical, agrophysical, agrochemical and electrophysical; cellulosolytic activity of the soil, water-soluble cations and soil pH. It was found that with a high share of sunflower in the crop rotation, water and physical indicators of soil fertility deteriorate. Most of the available moisture during the autumn-winter and early spring periods was accumulated in the sunflower field at a saturation of 20%. It was determined that the density of the tilth layer of soil in the studied variants was within the optimal range for sunflower – 1.07–1.11 g/cm3, with a slight increase in its values in the crop rotation with a saturation of 60 %. The best structured topsoil was observed under sunflower crops with a crop rotation saturation of 20 %, as evidenced by the structural coefficient of 1.2. It was found that the soil under sunflower crops had a low supply of easily hydrolysable nitrogen, an average supply of mobile phosphorus, and an increased supply of exchangeable potassium. It was determined that in the soil layer of 0–30 cm the pH value in the variants with 20 and 40 % saturation was within the range of neutral reaction of the soil environment – 7.0–7.3, which is optimal for growing sunflower. High microbiological activity of topsoil in a sunflower field with a saturation of 60 % was found. Especially important for electrical conductivity was the high presence of water-soluble salts of calcium cations, the correlation between these indicators was 1.00. The highest content of Ca2+ compounds was in the variant with a share of sunflower of 60 %. In the topsoil, its amount was at the level of 312 mg/l. With the saturation of crop rotations with sunflower by 20 and 40 %, a high yield of sunflower seeds was obtained. In these variants, it was at the level of 3.01–3.13 t/ha.
