Determination of critical phases of winter cereal crops based on international unified growth and development scales

Purpose. To establish the growth and development patterns of winter grain crops and determine vulnerable stages of their vegetation under deficit of environmental factors. Methods. Field studies were conducted in a zone of unstable moisture of the Right-Bank Forest Steppe of Ukraine at the experimental field of the Institute of Bioenergy Crops and Sugar Beet of the National Academy of Agrarian Sciences of Ukraine (50.023194, 30.173895) in 2020–2024. Results. The most vulnerable periods for the growth and development of winter grain crops are germination and tillering, as they play a key role in preparing plants for wintering. At the same time, the adverse factors that affect plants in winter are not critical, as with sufficient sugar accumulation and proper plant development in the Forest-Steppe of Ukraine, it is unlikely that adverse conditions will lead to plant death. Instead, most often critical plant conditions occur in the period from spring regrowth to flowering. In this period, the main elements of the yield structure are formed, and plants can significantly reduce their potential productivity. Stress in plants caused by soil moisture and nutrient deficits can be early determined using modern tools for assessing plant health. At the same time, the timely application of protective measures is unquestionable, as they are an important component of all modern cultivation technologies. Conclusions. For winter grain crops, the most vulnerable growth and development stages to moisture deficit are BBCH 00–09, 30–32, 41–69, high air temperature – BBCH 70–89, and nutrient deficit, particularly nitrogen deficit – BBCH 29, 33–36. At these stages plants are especially vulnerable to the impact of abiotic stress factors, which can significantly affect their productivity.