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Does straw retention sustain soil carbon stocks in Brazilian sugarcane fields?
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  • Sarah Tenelli,
  • Ricardo Bordonal,
  • MR Cherubin,
  • C Cerri,
  • João CarvalhoOrcid
Sarah Tenelli
UNICAMP
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Ricardo Bordonal
CNPEM
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MR Cherubin
USP ESALQ
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C Cerri
USP ESALQ
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João Carvalho
Orcid
CNPEM
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Abstract

Sugarcane straw is a crop residue known as the main input of carbon (C) to the soil, but its removal represents a valuable asset for bioenergy purposes, which may adversely affect soil organic C (SOC) stocks. Most studies related to this issue is limited to site-specific conditions and comprehensive studies in a wide range of soils and climate regions are scarce. This study was designed to evaluate temporal SOC stocks changes induced by sugarcane cultivation and straw management in the southern-central of Brazil. Ten field experiments were arranged in a randomized block design with four replications, including four straw removal rates: total (TR), high (HR), low (LR) and no removal (NR). Soil samples were collected to a 30-cm depth at the beginning of the trial establishment and after four consecutive years. The dataset suggested that 19% and 25% of the C added via straw were accumulated into the soil of the sandy and clayey areas, respectively. This study showed strong SOC depletion in sandy soils at rates of 1.4, 1.5, 1.9 and 2.3 Mg ha-1 year-1 under NR, LR, HR and TR, respectively. In contrast, clayey soils exhibited SOC accumulation over time, even removing all the straw from the soil surface. Based on SOC changes, these findings provide a robust scientific basis to support policy and management decisions for straw-derived bioenergy, showing that the removal of sugarcane straw may be potentially advantageous in clayey soils but should be avoided in sandy soils of tropical regions in Brazil.