Predicting soil C changes after pasture intensification and diversification in Brazil

•Long‐term predictions of soil C stocks and microbial biomass C were investigated.•Sustainable pastures management increased soil C stocks (0.4–0.95 Mg ha−1 yr−1).•Similarly, microbial biomass C contents also showed increases (3–40 mg kg−1 yr−1).•We calculated increases of 44–267% in the annual income for farmers.•Pasture intensification and diversification provided greenhouse gas mitigation. Globally, poorly managed pasture can contribute to increasing greenhouse gas (GHG) emissions. In Brazil, sustainable management systems are being proposed to reduce carbon dioxide (CO2) emissions and increase the soil C stock under degraded pasture. However, despite the potential benefits in the adoption of sustainable management systems, few studies have been carried out seeking to analyze their long-term effects on the soil C cycle. In this study, we used the DayCent model to simulate the effects of converting poorly managed pastures (PMP) to more-intensive and diversified systems of pasture management [fertilized pasture (FP), integrated crop-livestock (ICL) and integrated livestock-forest (ILF)] on long‐term soil C stocks and microbial biomass C (MBC). We also evaluated the effects of different pasture management scenarios for FP (fertilization frequency), ICL (time of implementation of the crop phase) and IFL (spacing between the tree rows). The DayCent model estimated that the conversion of PMP to FP, ICL and ILF increases the soil C stocks by 0.95, 0.04–0.70 and 0.16 Mg ha−1 yr−1, respectively. Similarly, the MBC contents also increased with conversion, mainly for ICL and ILF. In addition, the fertilization of the pasture every year (FP), the implementation of the crop phase within two years (ICL) and the spacing between the tree rows of 15 m (ILF) showed the highest soil C stocks and MBC contents. FP, ICL and IFL were also GHG sinks of 43, 57 and 116 Mg CO2eq ha−1, respectively. These results can help national initiatives associated with the recovery of degraded pasture in Brazil.