Tabachuk O. Substantiating the fertility of leached chernozem and increasing the productivity of sugar beet in crop rotations of the Right-Bank Forest-Steppe of Ukraine

For the first time, in the conditions of the Right-Bank Forest-Steppe of Ukraine, the high efficiency of alternative organic-mineral fertilization systems in forming the fertility of leached chernozem and the productivity of sugar beet in the conditions of short crop rotations was established. It has been proven that the application of mineral fertilizers, straw and green mass of white mustard under sugar beets stabilized soil fertility and ensured their high biological productivity. It was improved the system of alternative fertilization of sugar beets by applying nitrogen into pre-sowing cultivation and foliar fertilizing with micronutrient fertilizers. It was further developed the issue of the effectiveness of alternative organic-mineral fertilization of sugar beets in short crop rotations; the issue of nitrogen and trace element nutrition under alternative fertilization of sugar beets. It was established that the application of N90Ρ90Κ90 + straw + green manure in short crop rotations had the highest stabilizing effect on the humus condition of leached chernozem. The specified fertilization system ensured the supply of organic matter to the soil in the amount of 3.55-3.57 t/ha, stabilized the humus content in the 0-30 cm layer in the view of crop rotations at the level of 4.04-4.07%, increased the humus content to the background of mineral fertilizers - by 0.18-0.20% and provided humification coefficients of organic matter - 22-44%. The structure of crop rotation did not significantly affect the state of soil humus. It was investigated that the highest reserves of mineral nitrogen in the soil at the beginning of the sugar beet growing season were formed by the traditional manure-based fertilization system – 128-153 kg/ha, and among the alternatives, the best was the fertilization with the application of N90Ρ90Κ90 + straw + green manure – 99-112 kg/ha of nitrogen, while the mineral system of fertilization formed the lowest nitrogen reserves in the soil– 65-76 kg/ha. In crop rotations with predecessors of barley-peas and peas-vetch-oats, mineral nitrogen reserves were higher by 8-25 kg/ha than in crop rotation with two soybean fields. It was found that the alternative fertilization system with the application of straw, green manure and mineral fertilizers created a high background of mobile phosphorus and potassium in the soil at the beginning of the growing season – 183-193 and 103-115 mg/kg, respectively, which was at the level of the traditional manure-based system of fertilizers and exceeded the background of mineral fertilizers – by 18-22 and 26-34 mg/kg of soil. The crop rotation factor had an insignificant effect on the content of mobile phosphorus and potassium in the soil. It was investigated that organic-mineral fertilization systems formed reserves of productive moisture in a 1.5 m layer of soil 5-27 mm higher than mineral ones. Sugar beet most effectively used soil moisture in the crop rotations of barley-pea-winter wheat-sugar beet and soybean-soybean-winter wheat-sugar beet with the application of N90Ρ90Κ90 + straw + green manure: 305 m3 of moisture was used to form 1 ton of biological harvest with a decrease to the background of mineral fertilizers on 24-31 m3. It has been established that in conditions of sufficient moisture, organic-mineral fertilization systems are the most effective means of increasing the biological productivity of sugar beet in short crop rotations. The highest biological productivity of sugar beet was obtained in the rotation of barley-peas-winter wheat-sugar beets with application of N90Ρ90Κ90 + straw + green manure: yield of roots – 70.9 t/ha, sugar content –18.6%, sugar yield – 13.2 t/ha. The specified fertilization system increased sugar collection against the background of mineral fertilizers by 1.8 t/ha, compared to similar options in crop rotations with soybeans and peas-vetch-oats by 0.6 t/ha. It was investigated that the application of nitrogen fertilizers in the spring and foliar fertilizing with micronutrient fertilizers against the background of alternative organic-mineral fertilizers increased the yield of roots compared to the autumn application of nitrogen fertilizers – by 6.6 t/ha, sugar content in roots – by 0.2%, sugar yield – by 1.3 t/ha.