Abstract. Humusis the most important indicator of soil fertility. The main indicators of the soil largely depend on its quantity and quality: thermal, water, air properties, absorption capacity, biological activity. Plants, as biologicalobjects, throughout their lives not only use nutrients and moisture from the soil, but also enrich it by the excretionfromroots, dropping aging leaves, symbiosis with microorganisms, as a result of leaving the root mass and above-ground plant debris after harvesting. At the same time, asignificant part of the nutrients returnes to the soil, and the humus content in the soil increases. Crop residues and the root mass of crops are sometimes the only source of organic matter in the soil, an energy resource for the development of soil microflora. The potential for using organic residues is best manifested in crop rotation with proper crop rotation. This makes it possible to regulate the intake of fresh organic matterof different quantity and qualityinto the soil. The article presents thestudy of the effect of crop-root residues on soil fertility in a six-field crop rotation. The aimof the research is to conducta comparative assessment of the size of the input of plowedplant residues in the crop rotation and to determine their soil-improving efficiency. The experimental part of the work was performed on a stationary site of the experimental field of the Mari Agricultural Research Institute –branch of the Federal Agricultural Scientific Center of the North-East named after N.V.Rudnitsky. The experiment was repeated 4 times, andwas laid down by the method of split plots. As a result of the studies, it was revealed that in the control variant (grain-grass rota-tion) when using clover for 1 year, on average 3.02 t/ha of crop-root residues per year wasreceived. The greatest accumulation of organic matter was in the III crop rotation -3.37 t/ha. The enrichment of the soil with organic matter in the form of roots and stubble residues against the background of mineral fertilizers made it possible to maintain a deficit-free humus balance in the topsoil during four rotations of the studied crop rotations.