Abstract
AbstractGlobal demand for bioenergy increases interest in biomass‐derived fuels, as ethanol from sugarcane straw. However, straw is the main carbon source to soil and its removal reduces C input, affecting active fractions (dissolved organic carbon, DOC) and C storage. To quantify the effects of straw removal on DOC and C stocks, we built lysimeter system using soil (Rhodic Kandiudox) from sugarcane field. We evaluated four soil depths (1, 20, 50 and 100 cm) and four straw removal rates: no removal NR, medium MR, high HR and total TR, leaving 12, 6, 3 and 0 Mg/ha on the soil surface, respectively. After rainfall, drainage water was collected and analysed for DOC content. Soil C stocks were determined after the 17‐month. Total DOC released at 1‐cm depth amounted to 606, 500, 441 and 157 kg/ha in NR, MR, HR and TR, respectively. Net‐DOC suggests straw as the main source of DOC. Most of DOC in NR (50%) was retained within the 1–20 cm layer, resulting in higher C stock (10 Mg/ha) in the topsoil. In HR and MR, DOC retention was higher within 20–50 cm, suggesting differences in DOC composition. DOC in TR was 40% higher at 20 cm than at 1 cm, indicating C losses from topsoil. Low concentrations of DOC were found at 100‐cm depth, but representing 30% in TR. Straw removal for bioenergy production is sustainable, but we should leave at least 3 Mg/ha of straw to ensure DOC production and soil C storage, taking account the DOC contribution to key soil functions.
Highlights
Biomass energy is increasing worldwide as a strategy to reduce greenhouse gas emissions, mitigating climate change (IPCC, 2019)
We found different specific ultraviolet absorbance (SUVA, l/g cm−1) between treatments (Table S3), in which higher values suggesting presence of more recalcitrant materials while low values are associated with more labile materials
These effects are more relevant for surface soil layers, where straw removal reduces Dissolved organic carbon (DOC) concentration and total soil C stock, even in the short term
Summary
Coordination for the Improvement of Higher Education Personnel, Grant/Award Number: 2286 and 17; Fundação Agrisus; São Paulo Research Foundation, Grant/ Award Number: 2018, 09845-7, 03572 and 2016; Foundation for Research and Scientific and Technological Development of Maranhão; National Council of Technological and Scientific Development
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