The importance of alfalfa and its growth processes during harvesting phases in the conditions of the right-bank Forest-Steppe

The aim of the study was to investigate the impact of harvesting dates and fertilization levels on the height of alfalfa (Medicago sativa) plants in the conditions of the Right-bank Forest-Steppe. The research was conducted at the experimental field of Vinnytsia National Agrarian University with variants of different sowing rates (6.0-8.0 million seeds/ha) and four levels of mineral nutrition. In the sowing year, the lowest height of alfalfa plants was observed at the sowing rate of 8.0 million seeds/ha (63.4-64.4 cm), which increased to 64.4-66.3 cm at the sowing rate of 6.0 million seeds/ha. Complex fertilizers contributed to an increase in plant height from 0.9-1.9 cm to 1.0-2.7 cm compared to the control. It was found that plants, under stress conditions due to high air temperature and insufficient moisture at the root system depth, could not effectively absorb mineral fertilizers from the soil, which led to a reduction in growth rates. In the second year of vegetation, considering the hydrothermal conditions of the summer period, an impact on the growth processes of alfalfa was observed. This affected the plant height during both the cuts and the harvesting phases. After three cuts at the budding stage, the average plant height reached 54.3-54.5 cm, regardless of the sowing rate and mineral nutrition level. The results followed a sinusoidal pattern: the tallest plants were at the first cut (73.7-73.8 cm), with the shortest height during the second cut (41.4-41.8 cm), and a further increase to 47.7-47.9 cm at the third cut. At the beginning of flowering, the tallest plants reached 85.7-86.0 cm, while at subsequent cuts, made 40-41 days later, a decrease in height was observed: 43.9-44.4 cm at the second cut and 54.3-55.2 cm at the third cut. The average plant height at the sowing rates was 61.4-61.8 cm. Thus, alfalfa formed three full cuts during the growing season, with an average height of 54.3-54.5 cm. The tallest plants reached 76.8-85.8 cm with the application of mineral fertilizers at the dose of N35P90K150+S23.5Ca30Mg20, while the average values were 55.7-62.7 cm at a sowing rate of 6.0 million seeds/ha. The results of the study can be used to optimize the agrotechnology of alfalfa cultivation in the conditions of the Forest-Steppe