The influence of three doses of 2,4 dichlorophenoxyacetic acid - 30, 60 and 120 ml/ da on survival, growth and dynamics of accumulation of fresh biomass in g per plant in eight newly established Bulgarian lines, varieties and candidate varieties of soybean through various selection methods greenhouse conditions was studied. The objective of the study is to establish and compare the sensitivity of different soybean genotypes to 2,4-D amine salt. It was found that: The applied doses of 30, 60 and 120 ml/da Dicopur F (600 g/l 2.4 D amine salt) in growth stage three trifoliate leaves of soybean have a depressing effect on the survival of the tested genotypes in the following order: Srebrina (25.9%) -> F5 (Char x Williams) (26.4%) -> Divna (33.3%) -> M7 №18/4 (36.3%) -> Mira 96 (37.9%) -> Karina (38.1% ) -> Avigea (40.8%) -> Line №5c (57.7%);
It was found that 2.4 D amine salt has a statistically significant (P=0.05) inhibitory effect on stem growth in the cultivars Divna, Avigeya, Srebrina and Lines F5 (Char x Williams) and № 5c, while in the cultivars Karina, Mira 96 and Line M7 №18/4, where the differences are statistically unproven (P=0.05), this dependence can be explained by genetic differences, as the comparisons were made under the same conditions and doses of the applied herbicide.