Content and reserves of organic matter carbon in fallow and arable soils of the Omsk Irtysh region

The aim of the work is to establish the content and reserves of organic matter carbon in the soils of fallow lands and when introducing them into arable land in the natural and climatic zones of the Omsk region. The studies were carried out in 2022-2023 in the subtaiga (Tarsky district, Tara town), forest-steppe (Kormilovsky district, Sosnovka village) and steppe (Cherlaksky district, Preobrazhenka village) zones of the Omsk region on fallow lands of different ages: less than 10 years, 10-20 years and more than 20 years. The soil cover of the fallow lands in the subtaiga zone was represented by gray forest deep and medium-deep loamy and clayey soils; in the forest-steppe - by complexes of solonetz meadow-chernozem small and meadow-chernozem loamy and clayey soils; in the steppe zone - solonetz soils and solonetz complexes of solodized meadow-chernozem and chernozem-meadow small and medium soils. The aboveground phytomass of plant associations restored on fallow lands was 1.32-4.56 t/ha in the subtaiga, 1.39-1.92 t/ha in the forest-steppe, and 0.9-1.35 t/ha in the steppe zone. The largest reserves of organic matter carbon were found in postagrogenic soils of solonetz complexes of the forest-steppe (71-86 t/ha and 114-124 t/ha in the 0-20 and 0-40 cm layers, respectively). In the gray forest soils of the subtaiga they were smaller: 54-77 in the 0-20 cm layer and 91-117 t/ha in the 0-40 cm layer. The amount of carbon reserves in the 0-20 cm layer was the smallest in the solonetz soils of the steppe zone: 57-66 t/ha. In the two-year period after the introduction of young fallow soils into arable land, there were no significant changes in the carbon content in the 0-20 cm layer of deep gray forest soil. In the forest-steppe zone, the amount of carbon in the 10-20 cm layer of developed soil was greater than in the fallow land due to cultivation and high complexity of the soil cover. In the steppe zone, a decrease in the carbon content in the 0-10 cm layer of plowed solonetz soils was found.