Organic carbon balance during cultivation of various agricultural crops and fallow lands in the Northern Trans-Urals

The current study was conducted on leached blackearth of the experimental plot of the Northern Trans-Ural SAU located in the forest-steppe of the Trans-Urals in 2023–2024. The purpose of the study was to establish the organic carbon balance in leached blackearth during the cultivation of various crops and fallows in the Western Siberia. During the vegetation period, in all studied variants, carbon emissions increased from May to July and then decreased towards the autumn. In the moderately wet 2023, carbon losses due to soil respiration amounted to 2.4 t/ha in spring wheat crops, 3.2 t/ha in maize crops and 3.8 t/ha in alfalfa crops. In the excessively wet 2024, emissions increased by 46 % in spring wheat crops, by 16 % in maize crops and by 21 % in alfalfa crops. In the excessively wet 2024, the mass of plant residues was larger than in the moderately wet 2023 by 31 %, 22 % in wheat and maize crops, by 6 % and 26 % in alfalfa crops and in sown fallow. In the moderately wet 2023, the C org content in root and stubble residues was 0.7–2.5 % higher than in the excessively wet 2024. There has been determined that in the moderately wet year, carbon losses from the soil were -0.2 t/ha during spring wheat cultivation, -1.5 t/ha during maize cultivation, -1.0 t/ha in sown fallow and -1.8 t/ha in weedfree fallow. A positive balance of +0.2 t/ha was obtained only when cultivating alfalfa. In an excessively wet year, a negative carbon balance in soil was obtained in all the studied variants. It increased to -0.6 t/ha in wheat crops, by 13 % in maize crops, and to -0.5 t/ha in alfalfa crops. However, carbon losses decreased to -0.4 t/ha in sown fallow and to -1.3 t/ha in weedfree fallow.