Bioproductive сapacity of typical chernozem in the Left-Bank Forest-Steppe of Ukraine under favorable humid conditions

The article presents the results of research on the assessment of modern climate change and the impact of weather conditions on the yield of main field crops when using different feeding systems and tillage. It was established that during 1991-2020 the average annual air temperature in the region increased by 1,1oC, and the annual precipitation decreased by 5%. Under such conditions, the frequency of recurrence of highly and moderately arid conditions of the growing season increased from 47% in 1961-1990 to 61% in 1991-2020, however the probability of forming a sufficient  moisture supply decreased by half. Based on the results of the Climate Water Balance (CWB) assessment, it was specified that in the western part of the Left-Bank Forest-Steppe, according to average long-term data a negative WBC has been formed since June, and by the end of August its deficit reaches over 140 mm or 1,400 m3 / ha. In general, by the end of the period for 1991-2020, the deficit of WBC increased by 82 mm. Based on the information database made on the results of long-term stationary field experiment at Poltava Research Station of the Institute of Pig Farming and Agroindustrial Production of NAAS, the yield potential of main crops and the productivity of typical chernozem subject to the optimization of crop rotation and nutrient and water-air regimes, were evaluated. It was determined that optimization of crop rotations increases plant productivity by 19%, fertilizer systems - by 19-36%, irrigation - by 94%, irrigation and fertilization - by 130-153%, and a comprehensive combination of all agronomic measures - by 200% and more. It was also established that the total productivity of crop rotation under different systems of basic tillage remains virtually unchanged and enables to obtain average by year 3.6-3.8 t kd / ha against the background of natural soil fertility. From the organic fertilizer systems, the efficiency of using crop by-products as fertilizers is 10% higher than using manure and practically does not concede to organomineral fertilizer systems. As a result of research it was found that in the region in recent decades there is a tendency of deteriorating growing conditions of main field crops, which is reflected in the formation of low yields and poorer crop rotation productivity, significant variation of these factors in terms of weather, especially when having high soil fertility.