Decomposition of sugarcane straw: Basis for management decisions for bioenergy production

Highlights: • We tracked the sugarcane straw decomposition over two years under Brazilian conditions. • The lowest decomposition was associated with higher straw removal rates. • Straw removal did not impact the relative C and N losses. • The effects of removal rates on straw C:N ratio was site-specific. • C:N ratio, cellulose and hemicellulose content would be important predictors of decomposition changes. -- Abstract: Straw dead stock is a key driver for crop residue management decisions regarding bioenergy production. Therefore, a field study was conducted to evaluate the sugarcane straw decomposition under different straw removal rates, characterize straw composition changes, and quantify the straw-derived C and N loss. Four sugarcane straw removal rates were evaluated: no removal (14.0 Mg ha⁻¹ of DM), 25 (10.5 Mg ha⁻¹ of DM), 50 (7.0 Mg ha⁻¹ of DM) and 75% (3.5 Mg ha⁻¹ of DM) of straw removal. Our results showed that straw removal rate had no effect on first year of straw deposition, but during the second year, the lowest decomposition was associated with higher straw removal rates. Dry mass loss was also approximately 25% higher in the second year than in the first. Furthermore, carbon and nitrogen loss were two- and threefold higher in the first year compared to the second year of deposition. Overall, cellulose and hemicellulose decreased by 13 and 7%, respectively, while lignin increased proportionally by 92% during the two year experiment. Our findings suggest that the most appropriate removal rate to maintain soil quality and meet the demands for energy production is 50% of the total straw deposited on the soil.