Changes in soil carbon and soil carbon sequestration potential under different types of pasture management in Brazil

Abstract

There are currently 180 million hectares under pasture in Brazil, and despite the country being one of the largest meat producers, there remain around 64 million hectares that show signs of degradation and contribute to the substantial loss of soil organic carbon (SOC). The aim of this study, therefore, was to derive the factors for SOC stock changes in managed pastures and evaluate the potential for SOC sequestration when converting degraded pastures to well-managed or recovered pastures in Brazil. The study involved 169 paired comparisons, including different types of pasture spread over 14 states in Brazil, and analysed the data in linear mixed-effect models deriving the SOC stock change factors for various soil depths (30 to 100 cm) over 30 years since the change in management. The results showed that for 30 years at a depth of 0–30 cm, compared to native vegetation, nominal pasture (non-degraded grassland, but with no significant management improvements) and improved pasture increased SOC stocks by 15% and 8%, whilst degraded pastures reduced the stocks by 10%. However, the recovery of degraded pastures enhances the SOC by 23%. In terms of the rates of SOC change, pasture degradation leads to losses of 0.25 Mg C ha⁻¹ year⁻¹, whilst nominal or recovered pastures can sequester SOC at rates from 0.25 to 0.54 Mg ha⁻¹ year⁻¹. Overall, it was estimated that the recovery of degraded pastures can sequester up to 3445 Tg of CO₂. Nominal management or simple improvement practices can maintain or enhance SOC stocks, helping to mitigate the GHG emissions of livestock in Brazil.