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 (CL) by oxidation with 333 mM KMnO4. At the 2 locations in Australia, CT and CL 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 CT and CL at a depth of 0-1 cm than green cane trash management. At one of the sites, sugarcane cropping resulted in a decline in CT relative to the reference in the green trash management treatment but an increase in CL. In Brazil, trash management from one cane crop did not change CT over a 12-month period but green cane trash return increased CL. 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.