Diazobacterin is a biological preparation containing strains of bacteria Azospirillum brasilense 18-2 and 410. The bacterial titer in the preparation is not less than 2 billion CFU per gram. The preparation is available in peat and liquid forms, allowing convenient use for seed treatment or spraying of crops. Diazobacterin is used to increase yields of winter barley, buckwheat, and forage cereal grasses. The preparation helps improve plant growth by fixing atmospheric nitrogen, which contributes to increased soil fertility and agricultural crop efficiency. Using such biological preparations is an ecologically safe method for enhancing agricultural productivity.