Greenhouse gas emissions, carbon, and nitrogen stocks in a soil with different grass and legume cropping systems in the Brazilian Semi-Arid region

Different land-use systems are responsible for variations in greenhouse gas emissions and soil C and N stocks. The objective of this work was to estimate these variations in single, intercropped, and rotational cropping systems of two forage grasses and one legume (single pigeon pea, millet or sorghum; pigeon pea intercropped with millet; pigeon pea intercropped with sorghum; millet rotated with pigeon pea; and sorghum rotated with pigeon pea) in the Brazilian Semi-Arid region. Gas samples were collected weekly for ten months in static chambers positioned on the soil surface. The highest total N₂O emission was observed in single millet cultivation. Millet grown in rotation with pigeon pea and sorghum grown alone or in rotation with pigeon pea showed N₂O consumption. CH₄ fluxes were predominantly positive, except for the emission in millet in rotation. The other systems showed no difference in accumulated CH₄ emissions. No difference was observed between accumulated CO₂ emissions (global average of 232.2 mg C m^-2). N₂O fluxes were basal for most of the period, with positive and negative emission peaks. CH₄ fluxes showed positive emission peaks at the beginning of the experiment, but negative peaks occurred in millet grown in rotation, millet and pigeon pea intercropped, sorghum grown in rotation, and sorghum and pigeon pea intercropped. CO₂ fluxes were predominantly positive throughout the evaluation period, except for some negative fluxes in sorghum grown in rotation and in sorghum and pigeon pea intercropped. There was no variation in carbon and nitrogen stocks among the different cropping systems.