Effects of land-use types on soil carbon and nitrogen contents in the brazilian drylands

Brazilian drylands are highly sensitive to land-use change, increasing risks of soil organic carbon (SOC) and nitrogen (N) depletion and soil degradation. We evaluated SOC and N contents along depth profiles across three semiarid regions: Sobral (CE), Betânia do Piauí (PI), and Petrolina (PE). In Sobral, we compared native vegetation (NV), two crop-livestock-forest integration systems (CLFI 10 and CLFI 20; cultivated strips included maize and sorghum intercropped with Massai grass alternating with strips of native vegetation), and an intercropping system; in Betânia, NV and a crop-livestock integration system (CLI; cultivated land managed with sorghum intercropped with buffel grass); and in Petrolina, NV, grazed native vegetation, and buffel grass pasture. Soils were sampled at depths up to 60 cm in Sobral and 100 cm in Betânia and Petrolina, with SOC and N measured at each depth. Across sites, land-use effects were concentrated in upper layers. In Sobral, NV showed higher SOC and N at 0–10 cm than CLFI 10, while CLFI 20 and intercropping were comparable to NV; at 10–20 cm, intercropping showed the highest values, and below 30–60 cm systems converged. In Betânia, CLI maintained higher SOC at 0–10 cm, whereas NV showed higher N at 20–40 cm; at greater depths, both uses were similar. In Petrolina, buffel pasture had the lowest surface SOC, and N was weakly responsive to land use. Overall, dryland land-use impacts were mainly detectable in upper soil layers, highlighting the need for practices that sustain soil cover and biomass inputs to conserve SOC and N.