The effect of applying mineral and organic fertilizers on the sequestration of organic matter in sod-podzolic sandy loam soil and on its mineralogical composition was studied. Soil samples for research were selected at the plots of the long field experience "agrophysical station", laid down in MOS FBGNU AFI (Gatchinsky district, Leningrad region, Russia) in 2006, in the system of crop rotation: annual grasses - potatoes - barley + perennial grasses - perennial grasses 1st year of use - perennial grasses 2 nd year of use. The soil of the experiment is soddy-podzolic sandy loamy of two kinds of cultivation: medium (MC) - organic fertilizers were not applied and high (HC) - 520 t / ha of manure was introduced over three years. Doses of mineral fertilizers were calculated for a given productivity of photosynthesis, in each kind of cultivation, three variants: 1 - control - no fertilizers (efficiency of the PAR 1-2%); 2 - NPK1 (the efficiency of the PAR is 2-3%); 3 - NPK2 (the efficiency of the PAR is 3 - 4%). Sampling was carried out in the sowing of perennial grasses of the second year of use. The analysis showed that the highest number of Corg and Cclay is characteristic for the variant of the HC soil (p <0,0001) and is 23,78 - 27,57 g / kg and 74,14 - 76,96 g / kg, respectively. The content of Corg in the MC soil is 17,29 - 18,43 g / kg of soil, the Cclay of 56,1 is 61,15 g / kg of the fraction. A positive relationship between the content of the Сclay and minerals for the MC of the soil was fixed with respect to quartz (r = 0,96), dioctahedral and trioctahedral micas (r = 0,73-0,77). In the HC variant, such a relationship was found for feldspars (r = 0,87-0,99).