Scientific and Methodological Substantiation of Changes in the Density of Winter Wheat Crops in the Northern Steppe of Ukraine

Abstract

Objective. The main objective of our research was to substantiate the scientific and methodological basis for the development, implementation and adjustment of winter wheat cultivation technology based on the patterns of change in stem density in winter wheat crops during their vegetation period.
Methods. Field studies were conducted between 1986 and 2005 at Kirovohrad Research Station (now the Institute of Steppe Agriculture of the National Academy of Agrarian Sciences). Winter wheat was sown after black fallow and silage maize in three stages: 2, 17 September and 2 October.
Results. It has been established that from the time of emergence to the phase of full maturity, the number of plants in winter wheat crops decreases. On average, 43.7% of plants die during the growing season in crops planted after black fallow, and 47.5% after a non-fallow predecessor. Predecessors, sowing dates and the timing of spring vegetation recovery affect the intensity of winter wheat tillering in early spring. The earlier spring vegetation recovery occurs, the more intensively winter wheat plants tiller during this period.
With early sowing dates (2nd of September) after black fallow and silage maize, the highest stem density in winter wheat crops is observed at the end of autumn vegetation and subsequently decreases continuously regardless of the time of spring vegetation recovery. On average, stem density after black fallow decreases from 1748 to 543 stems/m2, and after silage maize from 1483 to 482 stems/m2. In late crops, in most years, the maximum stem density is reached in the BBCH 31 phase. After black fallow, the stem density of such crops at the end of autumn vegetation averaged 470 stems/m2, and in the BBCH 31 phase, it increased to 1043 pcs/m2, and in the phase of full maturity, the density of productive stems was 632 pcs/m2.
Conclusions. Predecessors, sowing dates and the timing of spring vegetation recovery affect the intensity of winter wheat tillering in early spring. The earlier spring vegetation recovery occurs, the more intensively winter wheat plants tiller in early spring. Plants sown late tiller more intensively in early spring compared to plants sown early. The maximum stem density of early crops sown on 2nd of September after both predecessors is achieved at the end of autumn vegetation due to high tillering of plants and subsequently decreases regardless of the time of spring vegetation resumption. The maximum density of late crops sown on 2nd of October, both on black fallow and after silage maize, in years with early, early and medium spring vegetation recovery is formed in the BBCH 31 phase.