Soil carbon stocks in sugarcane cultivation: An evidence synthesis associated with land use and management practices

Abstract

Biofuels are essential to ensure the energy transition and mitigating of climate change. However, understanding the impact of land use change (LUC) and management practices on soil organic carbon (SOC) stocks is fundamental to ensuring well-founded policymaking and assessing the sector's carbon footprint. Here, we conducted a meta-analysis (511 pairwise observations) to obtain Brazil's SOC stock change factors (SOC_scf) for LUC and management practices in sugarcane fields. Our results showed that converting native vegetation to sugarcane reduced the SOC stock in all assessed periods. The conversion from annual crops to sugarcane showed a reduction in SOC stock in the first 10 years but with a recovery over time. The conversion of pasture to sugarcane reduced the SOC stock only in the 10–20-year period and had a neutral effect in other periods evaluated. However, our dataset showed high variability in SOC_scf, with many observations indicating an increase in SOC stock, which is related to degraded pastures. We observed that the SOC accumulation rate for each ton of sugarcane straw was affected by the interaction between soil texture and precipitation. Regarding straw management, a low removal rate (< 34%) did not affect the SOC stock, while moderate (34%–66%) and high (> 66%) removal resulted in losses of 5.0% (SOC_scf 0.950) and 9.9% (SOC_scf 0.901), respectively. Our results also showed that reduced tillage and vinasse application increased SOC stocks by 24.0% (SOC_scf 1.24) and 10.0% (SOC_scf 1.10) respectively, proving to be good strategies to support C sequestration in sugarcane fields. Finally, we highlight that our results can contribute to the improvement of public policies and also be used in future life cycle assessment (LCA) and modeling studies, as they provide robust data to establishing regional SOC_scf induced by LUC and management practices, enhancing the reliability of the C footprint assessment of biofuel production.