Soil carbon changes in areas undergoing expansion of sugarcane into pastures in south-central Brazil

• Published in: Agriculture, ecosystems & environment ecosystems & environment, 2016-07, Vol.228, p.38-48
• Main Authors: Oliveira, Dener Márcio da Silva, Paustian, Keith, Davies, Christian Andrew, Cherubin, Maurício Roberto, Franco, André Luiz Custódio, Cerri, Carlos Clemente, Cerri, Carlos Eduardo Pellegrino
• Format: Article
• Language: English
• Subjects: Biofuels; C and N isotopes; Land use change; Soil organic matter; Sugarcane ethanol
• ISSN: 0167-8809; 1873-2305
• DOI: 10.1016/j.agee.2016.05.005

•Land use change decreases C and N stocks in soils of South-Central Brazil. The expansion of unburnt sugarcane into pastures recovers partially the C stocks.•The increasing on C stocks in sugarcane areas is related to more recently C inputs.•Shifts on C stocks regarding the sugarcane expansion are more noticeable below 0.5m.•Assessments on C stocks restricted to soil surface might be associated to bias. In Brazil, sugarcane expansion for ethanol production has been predominantly on areas previously used as pasture. Losses of C and N induced by land use change raise controversies about the environmental suitability of biofuel production. Therefore, we conducted a field study within the largest sugarcane-producing region of Brazil to evaluate the effects of the primary land use change (LUC) sequence in sugarcane expansion areas (i.e., native vegetation to pasture to sugarcane), on C and N dynamics in the top 1m soil layer. The LUC sequences caused substantial but varying changes in soil C and N stocks in areas undergoing expansion of sugarcane in south-central Brazil. The increase of C stocks in areas converted from pasture to sugarcane cultivation was 1.97Mgha−1yr−1, in contrast to conversion of native vegetation to pasture, which decreased soil C stocks by 1.01Mgha−1yr−1 for 0–1.0m soil layer. The use of 13C measurements to partition soil C sources showed that the greater C stocks in sugarcane areas compared to pasture was due to retention of the native-C stocks and increased accrual of modern-C comparing to pasture. Finally, the inclusion of deeper soil layers, at least down to 1.0m depth, is essential to assess the impacts of LUC on C balances in agricultural areas.