Peat reserves of the Russian Federation are estimated at more than 170.0 billion tons, it makes more than one-third of the world resources. The use of peat as a component for the preparation of composts is an important factor in increasing the productivity of agricultural ecosystems. During two cycles of four-course crop rotation ‘potatoes – barley – annual grasses – winter wheat’, we studied the influence of lowland peat, composted peat-poultry manure, cattle manure, their combined application with mineral fertilizers on soil physicochemical properties, nitrifying and cellulosolytic activity of soil and productivity of crop rotation. Application of cattle manure and composted peat-poultry manure contributes to the increase in the content of humus in soil by 0.07-0.16%, when combined with mineral fertilizers – by 0.14-0.22%, respectively. On average, the highest yield was noted in the variants with cattle manure and composted peat-poultry manure – 10.75-12.13 t ha -1 of grain units (g.u.), while in the check (without fertilizers) it was 8.03 g.u. (t ha -1). That is why peat is more profitable to use in the form of composts, especially as a component of composted peat-poultry manure.