Yield shortfall of cereals in Ukraine caused by the change in air temperature and precipitation amount

Aim. To determine the trends in precipitation patterns, the precipitation productivity, and the cumulative impact of the change in air temperature and precipitation levels on cereal yield, including corn and spring barley, throughout the vegetation cycle stages. Furthermore, the examination of the alterations in the climate suitability, crop yield shortfall, and their specific characteristics within in the soil-climatic zones of Ukraine during 1981–2010 years Methods. In order to accomplish the outlined aims conventional and more specific research methods were used: 1) An analytical- synthetic approach – to examine the existing state-of-the art research; 2) A statistical approach – to assess the intensity and significance of changes in agroclimatic conditions pertaining to crop cultivation; 3) A comparative analysis – to determine the specificities mentioned under 2) in soil-climatic zones of Ukraine and in different stages of plant development; 4) A climatic approach – to characterize precipitation levels and to evaluate their impact on crop productivity; 5) modelling – to assess the effect of changes in precipitation amounts on the productivity of corn and spring barley, to assess the cumulative impact of the variations in surface temperature and precipitation on climate productivity and yield shortfall of these crops; 6) application of abstract and logical method – to formulate the generalizations and draw conclusions based on the findings. Results. During the years 1981–2010, Ukraine experienced changes in precipitation patterns and increased air temperature throughout the vegetation cycle of corn and spring barley in different soil-climatic zones. These changes had implications for climate suitability and crop productivity. In the Polis- sia region, although there were increases in precipitation during most of the crops` growth cycle, the changes were insignificant and had a minimal impact on crop productivity, except during certain periods. Similarly, the cumulative coefficient of temperature and precipitation productivity showed low probability for changes in climate suitability and yield shortfalls in the entire Polissia region, maintaining avorable cultivation conditions for corn and spring barley. In the Forest-Steppe region, precipitation changes varied. There was an increase in the amount of precipitation in the western Forest-Steppe. The speed of these changes was 10–20 % in 10 years in certain areas, leading to decreased corn and spring barley productivity by 3–6 % over the same duration. The central Forest-Steppe witnessed increases and decreases in precipitation levels during specific crop development stages, negatively impacting productivity. The eastern Forest-Steppe had increased precipitation deficits during the vegetation cycle, resulting in reduced productivity. Overall, the changes in precipitation and the increased air temperature had unfavorable effects on field crop cultivation in the Forest-Steppe, particularly in the central region. Corn yield shortfalls of 3–5 % and spring barley yield shortfalls of 2–3 % were observed over each 10 years. In general, however, for spring barley favorable agroclimatic conditions persisted throughout the Forest-Steppe, and corn cultivation remained favorable in the western and satisfactory in the central and eastern areas. In the Steppe region, changes in precipitation levels were minimal, with fluctuations of 5 % over each 10 years. However, significant variations in moisture levels occurred during specific crop development stages. An increase in precipitation levels during the stage milky ripeness-middle dough phase of corn resulted in 3 % yield decrease over each 10 years. Spring barley benefited from increased precipitation during the tillering stage and decreased precipitation during the stagemilky ripeness and middle dough stages, leading to higher (precipitation) productivity. Overall, the considerable increase in air temperature and changes in moisture conditions in many cases adversely affected corn and spring barley cultivation, especially in the southern Steppe. These changes led to a 7–10 % decrease in corn climate suitability cultivation and 3–4 % decrease in spring barley over each 10 years. Corn cultivation conditions in the southern Steppe were deemed unsatisfactory, while those for spring barley remained satisfactory. Yield shortfalls due to the changes in air temperature and precipitation from 1981 to 2010 were 35–40 % for corn and 22–25 % for spring barley. Conclusions. The changes in precipitation and air temperature in Ukraine have significant implications for field crop productivity throughout the vegetation cycle. Decreases in precipitation levels during crop ripening stages and higher precipitation deficits during certain vegetation stages have resulted in reduced precipitation suitability and lower crop productivity. When combined with increased air temperature, these changes further contribute to decreased climate productivity and increased yield shortfalls for corn and spring barley. The most pronounced effects are observed in the Steppe region, particularly in the southern Steppe, where corn yield shortfalls due to air temperature and precipitation changes from 1981 to 2010 reached 35–40 % of the maximum potential yield under optimal climatic conditions, compared to 22–25 % for spring barley In contrast, the agroclimatic conditions for corn and spring barley cultivation in Polissia remained favorable throughout the observation period (1981–2010), regardless of changes in air temperature and precipitation. In the Forest-Steppe zone, conditions were favorable for barley cultivation and satisfactory for corn in the central and eastern areas. Abnormally high air temperatures coupled with precipitation deficits have resulted in higher yield shortfalls for cereals in significant areas of the country. The combination of increased air temperature and drier conditions underscores the diminishing potential of dryland farming in Ukraine, particularly in the Steppe region.