Influence of changes in air temperature on crop productivity formation in Ukraine at the turn of XX–XXI centuries (1981–2010)

Aim. To determine the tendencies in the changes in air temperature and their influence on the productivity of crops during the vegetative cycle periods, especially in soil-climatic zones of Ukraine for the 1981–2010 climate normals period. Methods. The analytical and synthetic, statistical, climatic methods, simulation (model of V.P. Dmitrenko “Weather-yield” (Dmitrenko VP et al, 2017, 2010), used to forecast the productivity of grains in the Ukrainian Hy- drometeorological Center since 1970), abstract-logical method. Results. The rising air temperatures were determined throughout the whole vegetative period of growing corn and spring barley over the period of 1981–2010. It was found that this rise in different phases of crop development was of different magnitude and relevance in all regions and soil-climatic zones of Ukraine. The reliable changes in the surface air temperature were noted in the phases of the third leaf, panicle emergence, and blossoming of corn in Polissia, Forest-Steppe, and especially Steppe (0.7– 0.8 °С/10 years, 0.8–0.9 °С/10 years and 0.9–1.1 °С/10 years, respectively). During the pre-sowing period, the periods of corn sowing and seedlings, the velocity of changes was twice lower in the whole territory of the country, and during the pe- riods of milky ripeness and middle dough – in the eastern Forest-Steppe and dry Steppe, amounting to 0.4–0.5 °С/10 years. A considerable rise in the temperature during the period of the third leaf, panicle emergence, and blossoming promoted the decrease in the influence of temperature during these phases of crop development, especially in the Steppe (up to 10–15 % in 10 years). Only the rise in the temperature during the pre-sowing period promoted the 3–6 % increase in the whole terri- tory of the country, and during the periods of milky ripeness and middle dough of corn – up to 8 % in 10 years in the Forest- Steppe and Steppe. Generally, the thermal conditions for corn cultivation deteriorated considerably but remained favorable in Polissia, satisfactory – in the Forest-Steppe and northern Steppe, and unsatisfactory – in the south, in the dry Steppe. The most intense changes in the air temperature during the vegetation period of spring barley were noted in the phase of milky ripeness and middle dough in all soil-climatic zones, amounting to 0.8–1.1 °С/10 years. During the sowing period, the phases of the third leaf, stem elongation, and ear formation, they were 0.6–0.7 °С/10 years, and during the pre-sowing period – 0.3– 0.4 °С/10 years. During the spring barley tillering phase, the change in the air temperature was insignificant in the whole territory of the country. A considerable increase in the air temperature was unfavorable for crop cultivation in all the soil- climatic zones of Ukraine during the vegetative cycle of spring barley, especially during the phases of milky ripeness and middle dough, and promoted the decrease in its productivity in Polissia, Forest-Steppe, and Steppe by 5, 7.5 and 10 % in 10 years, respectively. In general, the increase in the air temperature conditioned the deterioration in thermal conditions of cultivating spring barley but they remained favorable in Polissia and Forest-Steppe, and favorable or satisfactory in the Steppe during the pre-sowing period and the vegetative cycle.