This article discusses the humus content, which is one of the most important indicators of soil fertility and directly affects the productivity of agricultural land. In the conditions of Kostanay region, where chernozem and chestnut soils are subjected to prolonged agricultural use, the assessment of the dynamics of humus content is of particular importance. This work is based on long-term agrochemical studies covering the period 2012-2024 and is aimed at identifying spatial and temporal variability of humus content in the main types and subtypes of arable soils in the region. The presented data make it possible to trace the degradation changes, determine the patterns of humus reduction depending on soil and climatic conditions and agrotechnical techniques, as well as substantiate recommendations for the conservation and reproduction of soil organic matter. Scientific research was carried out within the framework of the BR24992785 project "Organization and conduct of comprehensive research to ensure the sustainable development of the agro-industrial complex of Kostanay region with the creation of a scientific and technological research center" with program-targeted funding from the Ministry of Education and Science of the Republic of Kazakhstan for 2024-2026.