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.

Aim. Research and evaluation of hybrid populations of (F3) alfalfa according to main agronomic characteristics for further use in breeding under conditions of high soil acidity. Methods. The field (phenological observations and records, hibryd analysis), laboratory (seed productivity accounting), mathematical-statistical (objective evaluation of obtained experimental data). Results. According to the research results of hybrid populations (F3) selected genotypes are tolerant to soil acidity with a relatively high forage and seed productivity, exceeding the standard sort of cyanosis on these indicators by 5–20 %. Conclusions. The evaluation has been performed and the promising starting material has been selected for four years planting alfalfa breeding (hybrid populations F3), which can provide a relatively high fee of dry matter (1.2–1.37 kg/m2) and seed yield (37.4–46.9) due to high soil acidity (pH 5.2–5.3). Keywords: alfalfa, soil acidity, seed yield, dry matter.

Further development of the livestock industry in our country depends primarily on the production of feed, their quantity and quality. The most effective way of solving this problem is to create and implement in the production of new varieties and hybrids of forage crops, which have higher yields of green mass, hay and seeds, better foliage and feed quality, intensity of regrowth in spring and after mowing, growing season, durability, stability to diseases and pests, winter hardiness and drought resistance and other features that determine their economic value. Another problem is the elimination of protein deficiency in the diets of farm animals by expanding the sown area under high-protein crops. The synthetic synthetics of alfalfa sowing Rodena was created on the basis of the hybrid population of Vinnichanka (Ukraine) x Vella (Denmark) at the Institute of Feed and Agriculture Podolia during 2003-2016. Posted in the state register of plants suitable for distribution in Ukraine, 09.11.2020 (Certificate of state registration of plant varieties of Rodena No. 200895 dated November 9, 2020, certificate of authorship on the variety of Rodena plants No. 16196001, Patent No. 210082 on January 19, 2021 ). When evaluating the feed and seed productivity of a variety on experienced fields of the Institute of Feeds, the advantage of Rodena varieties over the Syniuha Standard was established. Testing the suitability of a variety to distribute 8 points of research by the Ukrainian Institute of Examination of Plant Varieties confirmed higher rates of feed and seed productivity of the specified grade compared to the conditional standard. Creating a Synthetic Synthetic based on the use of clone genotypes, which, having a complex of economic and valuable signs, is highlighted by a high overall combinational ability, confirms the efficiency of this research direction. Rodena grade is recommended to use in clean and mixed crops with other perennial herbs for the production of high-quality feed in the soil and climatic zone of the Steppe of Ukraine.

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Aim. Evaluation of the source material on a set of economically valuable features and the creation with its participation of a synthetic variety of alfalfa. Methods. Field, laboratory, statistical. Results. The results of research and creation of a synthetic variety of sown alfalfa Rodena at the Institute of Forage and Agriculture of Podillya NAAS are presented. Entered into the State Register of Plant Varieties Suitable for Distribution in Ukraine (hereinafter - the Register of Plant Varieties of Ukraine). When evaluating the forage and seed productivity in the experimental fields of the institute, the advantage of the Roden variety to the Sinyukha standard variety was established. Extensive testing of the variety's suitability for propagation (PSP) in 9 research points by the Ukrainian Institute of Plant Variety Examination confirmed higher indicators of fodder and seed productivity of this variety in comparison with the conditional standard. Conclusions. The use of clonal genotypes, which, along with a set of economically valuable traits are distinguished by high overall combining ability, allows you to effectively create high-yielding varieties of synthetic alfalfa. Created in this way, the synthetic variety of alfalfa Rodena is recommended for use in pure and mixed crops with other perennial grasses for the production of high quality feed in the soil-climatic zone of the Steppe of Ukraine. Keywords: selection, alfalfa sowing, clone, synthetic variety, winter hardiness, dry matter, seeds.