Lucerne is a good soil conditioner, due to the strong root system, it protects the soil from water and wind erosion. It leaves an equal amount of organic substance, which contains 60-70 tons of manure. The purpose of research - the study of the dynamics of alfalfa agrocoenosis root system accumulation and the change of agrochemical characteristics of gray forest soils of Tatarstan under the influence of various factors. Experiments were carried out in 2008-2010 on an experimental field of State Scientific University “Tatar Scientific Research Institute of Agriculture”of Russian Agricultural Academy on Sarga variety of alfalfa herbage. In spring before the vegetation on the experimental zone we carried out a double-harrowing BIG-3 and added azophoska at the rate of 4 kg per hectare. The article presents the experimental data, obtained in the fertilizer application on the alfalfa forage on the gray forest soil in Kama region of the Republic of Tatarstan. Mineral fertilizers application gives an increase accumulation of the root system to 12-26%. In so doing, the activity of the decomposition of cellulose, comparing to the background without fertilizers, increased to 15-20%. Also on background of N72P72K72 , the phosphorus content in the soil rised at 54-80, potassium - 64-82, hydrolyzable nitrogen 2,8-6,8%.