Soil carbon changes resulting from sugarcane trash management at two locations in Queensland, Australia, and in North-East Brazil

Sugarcane cropping produces a large amount of crop residues, which offers considerable scope for residue management. Soil samples, collected from 2 long-term experiments in Australia and an experiment in Pernambuco State, Brazil, were analysed for total carbon (CT) and for labile carbon (C-L) by oxidation with 333 mM KMnO4. At the 2 locations in Australia, C-T and C-L concentrations were lower in the surface layer (0-1 cm) of the cropped soil compared with a nearby uncropped reference soil. Burning resulted in a greater loss in C-T and C-L at a depth of 0-1 cm than green cane trash management. At one of the sites, sugarcane cropping resulted in a decline in C-T relative to the reference in the green trash management treatment but an increase in C-L. In Brazil, trash management from one cane crop did not change C-T over a 12-month period but green cane trash return increased C-L. Sustainable sugarcane cropping systems must include crop residue return without burning in order to maintain an active C cycle in the system to drive nutrient cycles.