Abstract <p>The methane uptake and carbon dioxide emission by Albic Retisols (Aric) under the cultivation of green manure crops and perennial grasses, as well as the carbon accumulation in their phytomass were estimated at the Chashnikovo carbon supersite of Moscow oblast during the summer period of 2024. White mustard, vetch–oat mixture, perennial legume-cereal grasses, and giant miscanthus were studied. Greenhouse gas fluxes were measured using an automatic chamber, aboveground phytomass assessed by the mowing method, underground phytomass by washing roots from soil monoliths. The soils absorbed atmospheric methane at the rate of 0.15 to 0.62 mg C m^‒2 day^‒1. The highest total methane uptake over the summer was observed in soils under miscanthus at the rate of –0.047 g C m^‒2, it statistically significantly decreased by 1.6&#xa0;times in soils under the vetch–oat mixture, by 1.8 times under perennial grasses, and by 2.2 times under&#xa0;mustard. The total CO₂ emission by soils over the summer was maximum under perennial grasses (927.6 g C m^–2) and decreased under miscanthus (835.9 g C m^‒2), vetch–oat mixture (737.4 g C m^‒2), and mustard (476.6 g C m^‒2). The increased CO₂ emission by soils under perennial crops is due to more active root respiration during the formation of statistically significantly greater underground phytomass compared to green manure crops. The aboveground phytomass of giant miscanthus was more than 2 times higher compared to other plants. In total, over the growing season, the following carbon accumulation was observed in the phytomass: 536.0 g C m^‒2 in white mustard, 735.9‒755.3 g C m^‒2 in legume-cereal perennial grasses and vetch–oat mixture, and 2157.7 g C m^‒2 in miscanthus. Thus, the studied Albic Retisols (Aric) acted as a weak sink of atmospheric methane and emitted carbon dioxide in an amount less than or comparable to the carbon accumulation in the phytomass of green manure crops and perennial grasses. These data are important for the development of technologies aimed at reducing greenhouse gas emissions and increasing carbon sequestration in agroecosystems.</p>