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Over the course of 2007-2015, the department of the irrigated agriculture had been conducting research in the area of the Ingulets irrigation system on the experimental fields of the Institute of Irrigated Agriculture of the National Academy of Agrarian Sciences of Ukraine (NAAS), which were established in 1996, with the aim to develop and scientifically substantiate agroecological and technological methods for crop rotations on the irrigated lands of the Southern Steppe of Ukraine that will ensure soil fertility, increase crop productivity, economic and energetic efficiency. In 2007-2010, studies were conducted to substantiate the systems of basic tillage using different ploughing tools. The 4-field grain-row crop rotation 1 included winter wheat with post-harvest cultivation of millet, corn, soybeans and spring rape. Five studied systems of basic tillage differed in methods, techniques and the depth of soil loosening. In 2011-2015, grain-row crop rotation 2 entailed soybeans, instead of spring rape seed, and winter barley with post-harvest cultivation of millet, instead of winter wheat. Five studied systems of basic tillage differed in the depth of soil loosening and non-renewable energy costs for their implementation. Experiments were performed under conditions of two organo-mineral fertilizer systems using by-products of crop rotation, fertilizer application in doses of N75P60; N97, 5P60 and inoculation of soybeans with microbial compounds. Following crop rotations 1 and 2, a decrease in humus content within the 0-40 cm soil layer to the level of 1976, 110.2-114.4 t/ha, was observed. To prevent further decline in humus content, an optimization model was developed by capping specific weight of soybeans in short-term crop rotation 25%, stubble plowing the stem and leaf mass of crops as well as applying fertilizer quantities corresponding to the expected yields. With the help of mathematical modelling, it was determined that the retention of post-harvest plant remains in soil and the application of nitrogen and phosphorus fertilizers increased humus content in soil used for growing rape by 0.3%, winter wheat – by 0.7%, and corn – by 0.9%.

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The purpose. To determine agro-physical properties and water regime of soil at different systems of basic cultivation and doses of fertilizers, to calculate the level of yield of crops and productivity of crop rotation. Methods. Field and mathematical analysis. Results. Subsoiling systems of basic soil cultivation, and irrigation water form agro-physical properties which are optimum for growing winter barley and partially meet demands of corn and soya bean. Use as fertilizer of all collateral products of crops and increase of rate of application of nitrogen fertilizers from 75,0 up to 97,5 kg/hectare d.w. counting for 1 hectare of crop rotation square with inoculation of seeds of soya bean by Rizogumin promoted increase of productivity of crop rotation for 15,0-16,3% c. units according to systems of basic soil cultivation. Conclusions. In the tilling crop rotations on dark-chestnut medium-loamy soils in conditions of irrigation in the South of Ukraine it is expedient to apply system of the differentiated-1 basic cultivation with use as fertilizer of all collateral products and enter fertilizers in dose N97,5Р60. That will ensure profit at the level of 10 thousand hrn/hectare, and the level of profitableness 110%.

ЕФЕКТИВНІСТЬ АГРОЕКОЛОГІЧНИХ ЗАХОДІВ У СІВОЗМІНАХ НА ЗРОШУВАНИХ ЗЕМЛЯХ ПІВДНЯ УКРАЇНИ Р. А. ВОЖЕГОВА, доктор сільськогосподарських наук, член-кореспондент НААН, професор, М. П. МАЛЯРЧУК, доктор сільськогосподарських наук, с. н. с., А. С. МАЛЯРЧУК, кандидат сільськогосподарських наук, Інститут зрошуваного землеробства НААН В. О. УШКАРЕНКО, доктор сільськогосподарських наук, академік НААН, професор О. Є. МАРКОВСЬКА, доктор сільськогосподарських наук, с. н. с.