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Sugarcane straw is identified as a potential energy feedstock to increase bioenergy production, but advances are required in understanding the straw removal impacts on soil organic carbon (SOC) stability and storage. The main objective of this study was to evaluate the quantity, quality and physical protection of SOC under areas with different straw removal rates over a six-year period. A field experiment was conducted in randomized blocks with four replications, including the following straw removal treatments: total removal (TR), high removal (HR), low removal (LR), and no removal (NR), corresponding to the quantities of 0, 5, 10 and 15 Mg ha−1 of dry straw maintained on soil surface, respectively. Effects of straw removal on SOC stocks and its temporal dynamics, as well as the rates of carbon (C) incorporated into the soil were evaluated to a 0.3-m depth. The effects on particulate organic matter (POM) and mineral-associated organic matter (MAOM) fractions were evaluated through physical fractionation of SOM. Finally, it was evaluated the distribution of aggregates, the C content of aggregates and the C preservation capacity (CPC) in fractions of aggregates. Our findings revealed that TR and HR decreased SOC stocks at 0.0–0.1 m and 0.0–0.3 m depths. The data indicated that about 24% of the C added via straw were retained in soil, and NR showed a SOC accumulation rate of 1.42 Mg ha-¹ year-¹ relative to baseline. Low straw removal increased POM (46.2%) and MAOM (12.4%) in surface layer as compared to TR. The straw maintenance in the field increased the proportion of soil macroaggregates, resulting in higher amounts of C preserved in this fraction. Our findings suggest that maintaining 10 Mg ha-¹ of straw was enough to favor physical protection and sustain storage of SOC over time. Therefore, the surplus of straw could be removed to produce bioenergy, although this management may hinder soil C sequestration and its benefits for sugarcane production and climate change mitigation. • High and total removal rates of sugarcane straw reduced soil carbon stocks. • Low straw removal increased POM (46.2%) and MAOM (12.6%) compared to total removal. • Straw retention increased soil aggregation and preserved C in macroaggregates. • Low removal rate was enough to sustain physical protection and storage of soil C. [ABSTRACT FROM AUTHOR]

Bioenergy production from sugarcane can be one of the sustainable means of mitigating climate change. This was the central idea of the Conference, "Carbon Balance in the Sugar-Energy Sector," held in Brazil on September 14, 2021. The various panels showed that sugarcane stakeholders, including scientists, farmers, industrialists, and investors, are committed to making large-scale sugarcane production a key ingredient in the mitigation of climate change. Their strategies include sustainable land use and management practices to increase soil carbon sequestration; the large-scale production of biofuel, bioelectricity and bioproducts; negative emission industrial technologies; industrial waste recycling; and sector-specific policies rewarding farmers with carbon credits for avoided greenhouse gas emissions. Therefore, the sugarcane sector is not only key to promoting the social-economic development of Brazil, but also to promoting energy transition, curbing greenhouse gas emissions and consequently, reducing global warming and climate change. • Conference Report: 2021 Carbon balance in the sugar-energy sector. • Carbon Balance in the Sugar-Energy Sector 2021 Conference held by Luiz de Queiroz College of Agriculture (Esalq), University of São Paulo (USP), Piracicaba-SP, Brazil on September 14, 2021. • Sugarcane-derived bioenergy is a key ingredient in fighting climate change while simultaneously maintaining a balanced ecosystem (including enhanced soil health and increased capacity to sequester carbon) and promoting socio-economic development [ABSTRACT FROM AUTHOR]