The influence of hydrothermal factors on feed and seed productivity of alfalfa in conditions of the Right-bank Forest-Steppe of Ukraine

Relevance of the research is determined by the need to study the influence of the region’s hydrothermal resources on the alfalfa leaf-stem mass and seed yield formation, which is important in the present climate change conditions. In this regard, the article is aimed at identifying the influence of precipitation and temperature regime on the growth and development of plants of varieties and hybrids according to mowing cycles and years of grass stand use. In the research, the following methods were used: field (conducting phenological observations and records), laboratory (structural analysis of the grass stand), mathematical and statistical (objective evaluation of the experimental data obtained). It was found that the amount of precipitation from the beginning of the period of relative rest until the onset of active temperatures above 10˚C had the greatest influence on formation of the 1st mowing; the amount of precipitation after the establishment of active temperatures above 10˚С and up to the moment of the leaf-stem mass yield accounting had a moderate effect on the formation of the 2nd mowing and strong – on the 3rd one; the amount of precipitation of the previous mowing period – on the 2nd-4th one (the strongest – on the 4th); the sum of active temperatures above 10˚С – on the 1st and 3rd mowing; hydrothermal coefficient indicators – on the 2nd-3rd ones; duration of the growing season with active temperatures above 10˚С – on the 1st and 3rd. Seed yield, in contrast to feed productivity, largely depended on the amount of precipitation before the flowering phase and during the growing season of alfalfa in general. It was established that the yield of dry matter and seeds productivity are influenced by: the sum of active temperatures, the amount of precipitation per mowing or plant vegetation period, and the genetic characteristics of the hybrids and varieties under study. It was discovered that the hydrothermal conditions of the year differently influence the level of plant productivity – excessive and sufficient moisture increases feed productivity and reduces seed yield. The obtained data are of practical value for predicting the yield of the green mass of alfalfa in each subsequent mowing depending on the amount of precipitation during the previous growing season, as well as for the development of programs for the creation of synthetic varieties with the increased productivity rates of leaf-stem mass and seeds.