Modelling the trash blanket effect on sugarcane growth and water use

The traditional practice of burning at the pre-harvesting of sugarcane has being phased-out in Brazil, resulting in the maintenance of a crop s residue layer on soil surface, namely the Green Cane Trash Blanket (GCTB). New technologies for electricity and second-generation ethanol (2G) production from crop residues have raised the question on what would be the optimum amount of crop residue left on the field to keep the agronomic and environmental benefits of GCTB. To support informed decision making on sugarcane trash management, we updated, evaluated and applied a new version of the SAMUCA model to simulate the sugarcane growth and water use under the GCTB effect. The updated model was calibrated and parameterized for bare soil and GCTB conditions and evaluated across different Brazilian regions. Thirty-year simulations were then conducted with the updated model to quantify the effects of GCTB on sugarcane growth and water use where sugarcane is traditionally grown in Brazil. The updated version of SAMUCA model showed equal or superior performance when compared with widely-used process-based models for sugarcane. Based on our 30-year simulations, the GCTB exhibited a high probability to promote a beneficial effect on sugarcane yields in dry climates (>90%), with the potential for increasing, on average, 14 ton ha−1 of fresh cane yield in Petrolina, Brazil. Although the beneficial effect on yields were not significant in humid regions, the maintenance of 12 ton ha−1 of GCTB was associated with a high probability (>87%) in reducing the water use of sugarcane cropping system by 89 mm, on average, potentially reducing irrigation demand in the early stages of crop development while protecting crop production under dry spell events. The new version of SAMUCA model offers as a tool for decision making on mulch management in sugarcane plantations.