WINTER HARDINESS OF WINTER WHEAT IN THE CONDITIONS OF CHANGING CLIMATE
The aim of the work is to analyze changes in climatic conditions during the cessation of active vegetation of winter wheat (in November-March), and their impact on the problems associated with plant overwintering in the Southeast of the Central Chernozem region. The nature of changes in air temperature and precipitation over 40 years (19792018) in comparison with long-term data (1929-1978) was studied. Significant deviation of hydrothermal conditions over the analysis period compared to the long-term ones is revealed. Air temperature rose by 1.1-3.0°C and precipitation increased by 2.8-8.4 mm depending on the month of observation. A rise in air temperature and precipitation during the cessation of active vegetation create more favorable conditions for plant overwintering in the region. Over 40-year-long observation period, new favorable conditions for overwintering were observed in 77.5 % of cases, and the unfavorable ones in 7.5 %. There is a direct dependence of plant overwintering with an average monthly temperature in November (r = +0.65) and the 1st ten-day period in December (r = +0.34), the inverse one with temperature in January (r = -0.34) and precipitation in December (r = -0.33). At the same time, the risk of plant death from the impact of such negative factors as frost-killing, ice-covering and damping off is reduced, but it increases because of rotting and snow mold. Moreover, with the rise in air temperature in winter months, a new negative factor for the region began to intensify - rapid temperature change during the cessation of autumn vegetation (in November-December). During this time, conditions for mass destruction of aerial biomass with living tillering node are being created. Resistant to this factor varieties in the spring are able to regenerate and restore the required thickness of stand, the non-resistant ones either strongly thin or die.