New experimental data have been obtained in the stationary multi-year field experiment on sod-podzolic light loamy soil in 2016-2017. Actual yields of flax straw and seeds of «Levit 1» flax variety in 7-fields system with different levels of fertilizer doses are calculated using balance coefficients in «Mizorin» biological preparation application and without it. The influence of the mineral nutrition level and biological preparation on the indicators is studied, such as: the number of plants per 1 m2 before harvesting, the total and technical length of stems, the thickness of stems, the average number of fruitcases per plant, the average number of seeds in 1 fruitcase, the mass of 1000 seeds.