Changes in total soil organic carbon stocks and carbon fractions in sugarcane systems as affected by tillage and trash management in Queensland, Australia

The use of sugarcane trash (tops and residue) retention systems has been reported to lead to increases in total soil organic carbon (TOC) stocks. However, these increases have generally been small and confined to the top 0.05m of the soil profile. It has been hypothesised that the amount of TOC sequestered could be increased if the intensive tillage that occurs at the end of a sugarcane ratoon cycle, which is known to decrease TOC, could be eliminated. This research examined the effect of no-till management and/or trash retention on four trial sites throughout Queensland, to assess the ability of this management to increase TOC stocks. Management effects on particulate organic carbon (POC), humus organic carbon (HOC), and resistant organic carbon (ROC) stocks were also assessed using mid-infrared spectroscopy. No significant changes in TOC, POC, HOC, or ROC were observed over either 0-0.1 or 0-0.3m depth at any of the sites examined, when sites were considered as a whole. The results indicate that these management practices currently have limited capacity to increase TOC stocks on these soil types over 0-0.1 or 0-0.3m depth for the purposes of carbon sequestration.