Effects of different strains of Sinorhizobium meliloti on alfalfa (Medicago sativa L.) biomass yield

The effects of highly effective strains of Sinorhizobium meliloti on biomass and crude protein yields of alfalfa (Medicago sativa L.) were investigated in a three-year field experiment focusing on the advantage of alfalfa inoculation with N microbiological fertilizer over N mineral fertilization on chernozem soil. Strains 236 and 234 were found in this experiment to have significant effect on the yields of dry matter and proteins, by comparison to untreated control plants. In the third year of utilization, dry matter yield of alfalfa plants inoculated with strains 236 and 234 increased around 31% in the first cutting and 53% and 65% in the second one, compared to control plants. Strain 236 was found to increase the yield of crude proteins by 29.7% (second cutting) and 39.6% (third cutting) in the second year, and 27.5% (first cutting) and 50.3% (second cutting) in the third year of utilization, while strain 234 increased significantly the content of proteins in the third cutting of the second year (27%) and in the third year of utilization (51% in the first and 53% in the second cutting). The results indicate that effective strains of S. meliloti may be applied as N microbiological fertilizers on soils with optimal physical and chemical characteristics and autochthonous populations that may not have satisfactory effectiveness in nitrogen fixation.