Influence of ice crust on frost resistance and survival of winter wheat in the Steppe of Ukraine

The features of the effect both separately and together of lapped ice crust and low temperatures on winter wheat plants was highlighted. During the research period (2017–2019), the plants of the Mudrist Odeska variety which were damaged by low temperature and ice crust began to ear by 3–6 days later than undamaged ones. It was found that under unfavorable wintering conditions, in particular in plots without snow, the plant density per area unit and productive tillering, as well as grain productivity of the crop, largely depended on the degree of winter hardiness of plants. After growing of winter wheat which was frozen in laboratory conditions (without lapped ice crust) at a temperature of -15 °C, all plants survived, when the temperature dropped to -18 °C, 16.3 % of plants died. A further drop in temperature to -21 °C caused the loss of 81.7 % of plants. Against the background of artificially created lapped ice crust, the tillering nodes of the winter wheat plant were more damaged and, accordingly, the survival rate of plants decreased compared to variants without lapped ice crust, and at a freezing temperature of -15 °C its indicators were 69.8–92.0 %; at a temperature of -18 °C – 12.6–74.5 % depending on the thickness of the ice crust. When the cryogenic load increased to -21 °C, winter wheat died under the ice crust. During the growing season, in variants of mineral nutrition with a dose of N60P60K60, the death of winter wheat shoots compared with the non-fertilized control variant was less by 4.9–23.1 %. The dynamics of the soluble carbohydrate content in the tillering nodes indicates that at the resumption of spring vegetation the minimum consumption of carbohydrates by plants (30.8% of autumn reserves) was observed in variants with N60P60K60 fertilization. In the plots without snow cover under the lapped ice crust, carbohydrates were intensively consumed by plants, as a result, their amount in the tillering nodes during the winter period decreased on non-fertilized and fertilized variants by 58.5 and 61.2 %, respectively. Key words: winter wheat, frost resistance, mineral fertilizers, ice crust, productivity, survival.