Abstract <p>The results of a three-year study on efficiency of new microbial preparations under different conditions of mineral nutrition of spring wheat are presented. Seed inoculation with bio-preparations elevates grain weight by 21–39% against a PK background, whereas an increment from V417 bio-preparation comes to 39% as compared with the background, from strain V167—to 30%, and from standard strain Ch-13—to 21%. The yield increases by 46% with N₄₅ and by 58% with N₉₀ against an NPK background. No significant yield increments were observed with bio-preparations against an NPK background. Bio-preparations based on strains Ch-13, V167, and V417 produced a positive effect on the studied parameters: economic value coefficient (C_econ), productive tillering, spike length, weight of 1000 seeds, nitrogen and phosphorus accumulation in grain, payback from nitrogen fertilizer via increased grain yield, and the quantity of grain produced per 1 kg of consumed N. Preparation based on endophytic strain V417 was the most effective. As a result of the increased grain yield and straw weight with the use of nitrogen fertilizer and bio-preparations, the removal of nitrogen, phosphorus, and potassium rose bringing about a negative balance of nutrient elements. In the experiment, the product based on endophytic strain V417 was the most efficient.</p>