State and ways to increase soil fertility of the south-steppe zone of Ukraine

Abstract

Goal. To scientifically substantiate the modern landscape-ecological state of agricultural lands and the development of agrobiological measures to increase the fertility of degraded dark chestnut soils of the Steppe zone of Ukraine in conditions of natural moisture. Methods. Field — to study the interaction of the research object with biotic and abiotic factors of the Steppe zone; physicochemical — to establish the fertility of dark chestnut soil and to determine the chemical composition of plants; comparable calculation — to conduct the economic and energy evaluation of growing legumes of long-term grasses; dispersion analysis — to determine the reliability of the results of scientific research. Results. The area of perennial grasses in the Steppe zone over the past 10 years had significantly decreased. That created real risks to enhance the processes of water and wind erosions of soils. Significant influence on the efficiency of agricultural production in the Steppe zone also had regional climate change. In studies on the selection of perennial legumes and cereals as well as legume-cereal grass mixtures, accumulation of symbiotic nitrogen by Lucerne in the first year of the use of mono-species crops was 60 kg/ha, by mixture Lucerne + Bromus inermis — 68, and by Sainfoin — 105-118 kg/ha. In the 2nd year of the use of herbs, the accumulation of symbiotic nitrogen was also high — 37-55 kg/ha in Lucerne, and 52-80 kg/ha in Sainfoin. In the 3rd year of the use of grasses its accumulation decreased to 36-37 kg/ha in Lucerne, and to 15-22 kg/ha — in Sainfoin. The fractional composition of nitrogen in the 0-20 cm and 20-40 cm layers of dark chestnut soil after the 3-year use of Lucerne in comparison to other levels of crop rotation was the highest and depending on the soil layer made: of the total — 1006.3-1428.8 mg/kg, of mineral — 24,9-46,3, of alkaline hydrolyzed — 113,8-186,0, of heavy-hydrolyzed — 155,5-214,4, non- — 712,1-982,1 mg/kg of soil. Conclusions. One of the main areas of decrease in the processes of degradation and preservation and increase of soil fertility is the creation of high-performance mono-species agro phytocoenoses of perennial legumes and binary legume-cereal grass mixtures, resistant to regional climate change in the steppe zone of Ukraine.