Abstract: For the first time, in conditions of unstable moisture in the Right-Bank Forest-Steppe of Ukraine, the influence of by-products and mineral fertilizers on the fertility of podzolized chernozem for the cultivation of sugar beet in a chain with soybeans was determined. It has been proven that the use of winter wheat straw, optimization of doses and methods of applying nitrogen fertilizers and modernization of the fertilization system by applying straw destructor, microfertilizers and growth regulator ensure high yield and technological quality of roots on the basis of sustainability.
It was improved an alternative organic-mineral system of sugar beet fertilization by optimizing the doses and methods of applying nitrogen fertilizers, using a destructor, microfertilizers, and a growth regulator.
It was further developed the issue of modernization of the alternative organic-mineral fertilization system; the issue of optimizing doses of nitrogen fertilizers for alternative fertilization of sugar beet in conditions of unstable moisture.
It was established that the application of N60P50K53 + by-products per 1 ha of crop rotation stabilized the humus content of podzolized chernozem: in the 0-30 cm layer at the level of 3.06% with an increase to the initial level by 0.01%. The specified fertilization system formed the basis of sustainable cultivation of sugar beet in conditions of unstable moisture in the forest-steppe zone with a humification coefficient of organic residues - 4.18.
It was investigated that the alternative fertilization system with the application of N60P50K53 + by-products per 1 ha of crop rotation chain stabilized the content of alkaline hydrolyzed nitrogen in the soil: 0-30 cm layers – 104 mg/kg, 30-40 cm – 99 mg/kg of soil. Applying 90 kg/ha of nitrogen to pre-sowing cultivation on the background of 5 t/ha of straw + P90K90 under plowing created the most favorable conditions for nitrogen nutrition of sugar beet: the content of nitrate nitrogen in the layer 0-30 cm - 18.8 mg/kg, ammonium - 17, 8 mg/kg of soil with mineral nitrogen reserves in the soil – 110 kg/ha, exceeding the control without fertilizers by 37 kg/ha.
It was found that alternative straw-based organic-mineral fertilization systems ensured the stability of the pool of mobile phosphorus and potassium in podzolized chernozem. When applying 5 t/ha of straw + P90K90 under plowing, the content of mobile phosphorus at the beginning of the growing season of sugar beet in the 0-30 cm layer was 140-142, potassium - 100-104 mg/kg of soil, with an advantage over the control without fertilizers - by 6-8 and on 14-18 mg/kg of soil. At the end of the growing season, the content of mobile phosphorus in the soil decreased by 1.24-1.31 times, potassium - by 5-24%.
The results of the research established that biologization and modernization of the fertilization system provided the highest efficiency in the use of moisture from the soil by plants. Under the application of 5 t/ha of straw + Filazonite, 10 l/ha + P90K90 under plowing + N90 in pre-sowing cultivation + "Folcrop combi" + "Folcrop amin" moisture consumption for the formation of 1 t of yield - 329 m3 with a decrease to control without fertilizers by 104 m3.
According to the results of research, it was found that in conditions of unstable moisture, the use of N60P50K53 + by-products per 1 ha of rotation chain was slightly inferior to the traditional manure-based fertilization system - a decrease in the yield of roots - 4.1 t/ha, in sugar yield - 0.6 t/ha with absolute indicator values of 47.7 and 8.2 t/ha, respectively. Biologization and modernization of the fertilization system with the application of 5 t/ha of straw + Filazonite, 10 l/ha + P90K90 under plowing + N90 in pre-sowing cultivation + "Folcrop combi" + "Folcrop amin" in the leaf closing phase in the rows ensured the maximum productivity of sugar beet: yield of roots – 60.9 t/ha, sugar yield – 10.54 t/ha with growth compared to control without fertilizers – by 19.7 and 3.22 t/ha. The specified fertilization system significantly improved the technological quality of roots and reduced sugar losses in molasses by 0.04-0.05%.
It was investigated that alternative organic-mineral systems of fertilization of sugar beet, which provided the application of mineral fertilizers in the dose of N90Р90K90, formed a positive balance of nutrients in the soil in the case when the leaves of sugar beet left on the field: nitrogen in the amount of 0-20 kg/ha, phosphorus - 53 -61, potassium - 2-23 kg/ha. Under the alienation from the field of roots and leaves of sugar beet, the fertilization system was unbalanced in terms of nitrogen and potassium and was accompanied by a nitrogen deficiency in the soil in the amount of -40-79, potassium – of -49-91 kg/ha.
