Based on previously published works, a digital assessment of the effect of fertilizers on the yield of various agricultural plants was carried out. The new technique involves the use of the growth factor action coefficient, which is numerically equal to the relative rate of yield increase with an increase in the amount of fertilizers (nutrients) in the soil. Calculations were carried out for different natural and climatic conditions and different types of plants. It has been established that nitrogen fertilizers have a stronger effect on the yield than phosphorus and potassium fertilizers. A new methodology for assessing the effect of fertilizers on the yield of agricultural plants can be used to calculate the optimal doses of different fertilizers for different plants and a proposed method – for determining doses of fertilizers based on laboratory, growing or field experiments based on the yield (growth) of a particular plant in certain soil and climatic conditions. Known methods for calculating doses of fertilizers for specific plants and soil-climatic conditions, such as ‘calculating doses of fertilizers based on the removal of nutrients, taking into account the properties of the soil’ not accounting the content of mobile forms of fertilizer elements in the soil and plants, as well as changes in the supply nutrients in the soil, etc., ‘determining doses of fertilizers based on data from field experiments’ are essentially “heuristic”. They do not take into account the physiological characteristics of the influence of fertilizers and other factors on plant growth and productivity. The formulas proposed here take into account only approximate functional connections obtained from experimental data. Unlike the well-known method of elementary balance for determining doses of fertilizers, or the method of calculating doses of fertilizers according to the amount of nutrients required to increase the yield by 1 centner, etc., the proposed method, firstly, takes into account the value of the yield obtained without fertilizing the soil, secondly, the maximum potential value of the yield is determined and taken into account and, finally, the supply of nutrients in the soil is taken into account.