Search

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 (SOCscf) 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 SOCscf, 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% (SOCscf 0.950) and 9.9% (SOCscf 0.901), respectively. Our results also showed that reduced tillage and vinasse application increased SOC stocks by 24.0% (SOCscf 1.24) and 10.0% (SOCscf 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 SOCscf induced by LUC and management practices, enhancing the reliability of the C footprint assessment of biofuel production. [ABSTRACT FROM AUTHOR]

The formation of strongly weathered soils of the tropics (Ferralsols) with high carbon stocks (thick A‐horizon/umbric horizon) is still not understood. In order to contribute to the understanding of the formation of Umbric Ferralsols, we studied these soils in the highlands of Rio de Janeiro state (Brazil) from various perspectives. We analysed soil morphology, micromorphology, physical and chemical soil attributes, soil phytolith assemblages, and δ13C isotopic composition in a multi‐proxy study. The profiles presented ferralic horizons with SiO2/Al2O3 ratio (ki index) < 1.0, low silt/clay ratio values, predominance of kaolinite and presence of gibbsite, and low cation exchange capacity. These characteristics indicate a high degree of weathering and ferralitization. The isotopic and phytolithic variations indicate climatic modifications during the Late Holocene (approximately 2300 years ago), with a predominance of mixed vegetation composed of plants of the C3 and C4 photosynthetic cycles. This condition favoured the accumulation of organic matter in the Umbric Ferralsols. The accumulation of organic matter in subsurface B horizons occurred under drier past climatic conditions in a savanna environment, which may have favoured the occurrence of fires, thereby explaining the charcoal fragments identified in the micromorphological analyses. In contrast, the development of the umbric horizon in the profiles was favoured under wetter environmental conditions than the present environmental conditions, and favoured the development of vegetation and intense accumulation of organic material on the surface and at depths close to 100 cm. The pedogenesis of umbric horizons in Ferralsols reinforces the importance of bioturbation in the incorporation of organic matter, intensifying the humification and resulting in a strong darkening of the soil (melanization). [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Agricultural Sciences / Revista Brasileira de Ciências Agrárias is the property of Universidade Federal Rural de Pernambuco and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)