SURVIVAL OF WINTER WHEAT CROPS IN THE NORTHERN STEPPE OF UKRAINE
Authors:   Central Ukrainian National Technical University, Ukraine, Mostipan Mykola 
Published: February 2023

The subject of the study was the dynamics of plant density in winter wheat crops during the growing season. The main goal of the research was to provide scientific and methodological foundations for the development, implementation and correction of the technology of growing winter wheat in the Steppe zone of Ukraine based on the dynamics of plant density during growing season. Winter wheat was sown after black fallow and corn for silage in three terms: September 2; September 17 and October 2. Plant density records in crops were carried out in the phase of full germination, at the end of autumn vegetation, at the time of renewal of spring vegetation and at the phase of firm grain maturity.It was established that in the conditions of the northern Steppe of Ukraine, during the entire growing season, from the time of emergence of seedlings to firm grain maturity, an average of 47,4 % of winter wheat plants survive. When growing winter wheat on black fallow, the survival rate of plants is higher and is 49,8 % compared to the fore-crop corn for silage – 44,9 %. Early sowing (September 2) reduces the survival rate of winter wheat plants on black fallow to 45.1 %, and after corn for silage to 39,6 %, compared to 52,1 % and 47,4 %, respectively, for the fore-crops when sowing on October 2. The highest survival of plants is observed during the autumn period and is 95,1 % on black fallow, and 94,1 % after corn for silage. During the winter period, plant survival is on average 70,2 %, and during the spring-summer vegetation period it is 73,7 %. Early seeding reduces plant survival compared to late seeding after both fore-crops in the winter period and, on the contrary, increases it during the spring and summer vegetation.Extending the duration of the period from the time of the cessation of vegetation in the fall to its renewal in spring reduces the survival of winter wheat plants. In years with the length of this period exceeding 130 days, the survival rate of plants on black fallow decreases to 65,5 %, and after corn for silage to 51.1 %, against 72,1 and 81,8 %, respectively, in the years with the duration of the indicated period up to 110 days. Early sowing on September 2 ensures lower survival of winter wheat plants during the winter period compared to sowing on October 2, regardless of its duration.The early and middle renewal of spring vegetation ensures higher survival of winter wheat plants during the spring-summer vegetation compared to the late one in the first decade of April. In years with early and medium spring vegetation renewal, the survival rate after corn for silage plants is 81, %7 and 80,4 %, respectively, against 59,2 % in years with late renewal.When seeding winter wheat after a non-fallow fore-crop, the greater the reserves of productive moisture in the soil at the beginning of the booting phase is, the higher is the survival of the plants during their spring and summer vegetation. This dependence can be traced in all crops of different ages. In years with the content of productive moisture in the meter layer of the soil up to 90 mm, plant survival is on average 64,5 %, while in years with a moisture content of more than 120 mm, it increases to 79,5 %.In the Northern Steppe of Ukraine, the largest share of plants from the total number of all dead plants during the growing season dies during the winter period, and the smallest – during the autumn growing season. On average, these indicators are 53,9 % and 10,1 %, respectively. During the spring and summer vegetation, an average of 35,9 % die. Shifting the sowing dates from September 2 to October 2 after both fore-crops reduces the proportion of dead plants during the winter period and at the same time increases their number during the spring-summer vegetation period. Sowing on September 2, the share of dead plants during the winter period is 65,6 %, while sowing on October 2, it decreases to 49,4 %, and after corn for silage, these indicators are 56,7 % and 46,5 %, respectively. At the same time, the share of dead plants during the spring-summer growing season on black fallow grows from 22,2 % to 41,8 %, and after corn for silage from 31,4 % to 43,9 %.