The paper presents the results of the study examining morphological features of root system and their connection with herbage in different alfalfa genotypes, represented by the following varieties and populations: Louise, Zoryana, Nadezhda, Unitro, Seraphim, RK/98, PR-04, MO-115, SV, HMG. The study was conducted within 2015-2018 in the field conditions at the Institute of Irrigated Agriculture of NAAS at the dark-chestnut soil. The crop cultivation technology was standard for the irrigated conditions of the zone of the study conduction. The experimental data were processed by the generally accepted procedure of the analysis of variance and Pearson’s correlation analysis. The results of the study testify about the significant differences in root system morphology in different genotypes of alfalfa, and their unequal value for plant breeding work. The varieties Zoryana, Seraphim and the population MO-115 with a high volume of the root system of 6.9-7.0 milliliters and the established links between the studied features of subsurface and herbage biomass are recommended to be used in further alfalfa breeding work