The influence of mineral and organo-mineral fertilizer systems in the Geonet of long-term experiments on the formation of carbon balance in the agroecosystem

The purpose of the work was to assess the effect of mineral and organo-mineral fertilizer systems on the balance of greenhouse gases (CO2 and N2O) in the agroecosystem wile winter wheat producing. The experiment was conducted 2021–2024 in the steppe zone of the Kabardino-Balkarian Republic (Tersky District, Opytnoye Village) on a site of long-term experiments included in the Geosystem (No. 037). The soil of the site is represented by ordinary micellar-carbonate chernozem. The calculation of the carbon dioxide balance was carried out in accordance with the methodological recommendations of the Ministry of Natural Resources and Environment of the Russian Federation (Order No. 371 dated May 22, 2022). The volumes of nitrous oxide emissions were determined in accordance with the recommendations of the Intergovernmental Panel on Climate Change. By comparing the CO2-eq balance data in the agroecosystem and the CO2-eq corresponding to the amount of N2O emitted from the nitrogen contained in plant residues and fertilizers, as well as the mineralizable nitrogen in the soil, the most climate-friendly (carbon sequestration capacity) system was identified. The average amount of CO2-eq accumulated in the “soil–plant” system over 4 years under the organo-mineral fertilizer system was 98.5 t/ha, compared to 28.7 t/ha under the mineral system. These figures reflect the difference in carbon balance compared to the control option, which did not use any fertilizers. The main absorber of CO2 was the soil, both in the topsoil and in the subsoil (0–40 cm). In the organic-mineral system, the accumulation of carbon in the soil was 25.2 t/ha (92.2 t/ha CO2-eq). In the mineral system, it was 7.3 t/ha or 26.7 t/ha CO2-eq.