This study aimed to assess the soil carbon stock under cultivated pastures in the Parnaíba River basin. A set of 80 soil samples were collected randomly in the basin, 40 in degraded pastures and 40 in improved pastures, at the following depths: 0-5, 5-10, 10-20 and 20-30 cm. Soil texture, bulk density, total carbon content (%) and carbon stock (Mg/ha) were the variables considered. Overall, both degraded and improved pastures occupy areas of similar soil texture, however, the soil bulk density under improved pastures presented lower values than that from soils under degraded pasture. The bulk density increased with the increasing soil depth in both types of pastures. The soil carbon content decreased with soil depth regardless of the pasture´s management condition. On average, improved pastures, in comparison with degraded pastures, presented higher soil carbon contents at all considered soil depths. The surface layer (0-5 cm) showed the highest soil carbon contents on average and for both improved pastures (2.6%) and degraded pastures (1.9 %). Considering all soil depths (0-30 cm), improved pastures had an average soil carbon content of 68.28 Mg/ha, while degraded pastures presented an average soil carbon content of 59.35 Mg/ha. Well-managed pastures can store carbon throughout the entire soil depth considered in this study (0-30 cm) upt to 15% more carbon than in degraded pastures, emphasizing the importance of pasture management as a way of seeking carbon from the atmosphere and stock it in the soil. In a scenario where all degraded pastures are converted into improved pasture, we can have an additional 41 Tg of carbon stocked in the Parnaiba river basin.
pastures; carbon stocks; Paranaiba River basin
