Typical hydrothermal conditions of the Right-bank Forest-step zone and their influence on corn productivity

Abstract

Corn is a highly productive crop of universal purpose, which is grown for food – 20–25 %, forage – 60–65 and technical purposes – 15–20 %. Increasing its yield is possible due to the improvement of the elements of the technology of cultivation taking into account biological characteristics. The growth and development of corn, the production of high yields, as well as the improvement of the quality of the main products are determined by factors of anthropogenic origin and weather conditions. Hydrothermal conditions of Ukraine have already begun to change significantly during the last decades, which resulted in a shift in the climatic seasons, changes in the vegetation period duration (depending on the zone and the biological features of the crops it can either decrease or expand), the decrease in the duration of a stable snow cover, changes in water resources of local drainage. The period 2005–2016 was analyzed for the reliable estimation of the typicality of weather conditions and their influence on the corn productivity under the following basic cultivation methods: ploughing at the depth of 28–30 cm (control), flat-cut tilling at the depth of 28–30 сm, chisel ploughing at the depth of 43–45 cm and disking at the depth of 10–12 cm. The dynamics of precipitation in the northern part of the Right Bank Forest Steppe during the corn vegetation period for the last 2005–2016 testifies to the noticeable tendency of increasing the amount of precipitation in May-June and their sharp decrease in July-August. It was determined that the conditions for eight years – 2006–2008, 2011–2014 and 2016 were optimal for their hydrothermal indices for the production of corn yields at the level of 5.83–9.47 t/ha. The hydrothermal coefficient for vegetation was 1.13–1.76. Weather conditions were unfavorable in 2005, 2009–2010, and 2015 with the amount of precipitation for vegetation of 120–288 mm, which is below the long-term amount by 120 mm, or 36 %. The peculiarity of these years was 37–61 % lower precipitation level in June–July with the grain yield of 3.12–6.51 t/ha. The mathematical-statistical analysis allows to characterize features and typicality of weather conditions of 2005–2016 and to estimate the influence of hydrothermal years and separate months on corn crops productivity. It has been established that there is the following correlation between weather conditions in July and the yield of corn: high correlation for disk soil cultivation (r=0.75–0.86), the average – for ploughing and chyzel loosening (r=0.49–0.53). Thus, the formation of a deep layer of soil with the best water–physical characteristics and fertility in these cultivation modes reduced the dependence of the elements of yield formation from the adverse weather conditions and provided a higher yield of corn by 6.0–8.0 %. Key words: hydrothermal conditions, hydrothermal coefficient (HTC), vegetation period, corn yield.