Dark gray forest soils humus state of the Northern Trans-Urals

The purpose of research is to study the humus state of virgin dark gray forest soils on the territory of the subtaiga and forest-steppe zones of the Tyumen Region in order to understand the direction of the soil-forming process. For the period from 1960 to 2020, 123 full-profile sections were laid and described, soil samples were taken for laboratory analysis. Statistical processing of the results was carried out in MS Excel. It was found that the average humus content in horizon A1 is 5.71±1.19 %. Dark gray soils with a content of humus above the average for the sample predominate, which indicates an improvement in their humus state in the course of natural development. The A1 humus horizon of dark gray forest soils contains 0.37 ± 0.10 % total nitrogen. The ratio of carbon to nitrogen in the humus horizon is 9.21±1.12, which indicates a high quality of humus. In the upper part of the illuvial horizon (B1), the average content of humus in the sample is 0.80±0.37 % with a range of variation from 0.14 to 1.52 %. The coefficient of variation is 46 %, which corresponds to a high degree of heterogeneity. The lower part of the illuvial horizon contains the minimum values of humus, which vary from 0.02 to 1.21 %. Humus reserves in the A1 horizon of dark gray forest soils average 189 t/ha with a wide range of variation from 74 to 315 t/ha. The dark gray forest soils of the Northern Trans-Urals are characterized by a favorable humus state; they develop mainly as a soddy type with a gradual accumulation of humus in the upper part of the soil profile with a tendency to decrease its enrichment with nitrogen. This makes them the most promising for involvement in agricultural turnover with the expansion of the arable fund in the Northern Trans-Urals.