Humus state of chernozem soils of unused arable land of Kansk forest-steppe

The aim of the study is to assess the humus status of chernozems of unused arable land in the Kansk forest-steppe. Studies to assess the humus status of chernozems in the Kansk forest-steppe were con-ducted by the Federal State Budgetary Institution of Agricultural Sciences Solyanskaya of the Rybinsk Dis-trict in 2022–2024. The object of the study is the most common subtypes of chernozems (podzolized, leached, ordinary) of unused arable land in the Kansk forest-steppe of the Krasnoyarsk Region. Chernozems of the Kansk forest-steppe were characterized by a gradual distribution of humus with depth, but had differences at the subtype level in its content within the profiles. In podzolized chernozems, humus accumulation was noted in the half-meter soil layer; in leached and ordinary chernozems, humus accumu-lation occurred in the 0–30 and 0–20 cm layers. An assessment of the average statistical humus content in the humus-accumulative horizons of podzolized and leached chernozems showed a high level of humification (7–6 %) with an average variability of the feature in space (Cv = 24 %). The differences in the thickness of the humus horizons of these subtypes determined the increased variability of the indicator with a depth of up to 32–62 %. In ordinary chernozems, the average humus content of soils in the A hori-zon was accompanied by a slight variation of the indicator within the entire profile (Cv = 13–16 %). The nature of the genetic horizons and the subtype level of chernozems were the factors determining the features of the statistical distribution of humus in space. Podzolized chernozems were characterized by high humus reserves in the 0–20 and 0–100 cm layers (183–389 t/ha). In leached chernozems, they amounted to 142 and 249 t/ha, respectively, in ordinary chernozems – 116 and 211 t/ha, which corre-sponded to the average humus reserves. With an average enrichment of humus with nitrogen in humus-accumulative horizons, a narrowing of the indicator to 8–10 was noted in leached and ordinary chernozems. Down the profile, the C:N ratio in these soils corresponded to a high and very high supply of humus with nitrogen.