Summary
Blair, Lefroy and Lisle present a practical methodology for fractionating soil carbon by oxidative lability and introduce the Carbon Management Index (CMI)—a composite metric combining changes in total carbon and lability to assess soil health under agricultural management. Field data from cereal, legume and sugarcane systems in Australia and Brazil demonstrate that the CMI is sensitive to management-induced changes in soil carbon quality, declining with intensive cropping but improving with legume integration and green trash retention. This framework provides a quantitative tool for monitoring soil sustainability in agricultural systems.
Regional applicability
The methodology was developed and validated in Australia, making it directly applicable to United Kingdom farming systems. The temperate cereal and mixed farming systems examined in New South Wales parallel UK conditions, whilst the sugarcane and tropical systems from Queensland and Brazil illustrate how the CMI can be adapted across diverse agroecologies. The permanganate fractionation procedure and CMI could support UK soil carbon accounting and management effectiveness assessment.
Key measures
Total soil carbon (CT) by combustion; labile carbon (CL) oxidised by 333 mM KMnO₄; non-labile carbon (CNL) resistant to permanganate oxidation; Carbon Pool Index (CPI); Lability Index (LI); Carbon Management Index (CMI = CPI × LI × 100)
Outcomes reported
The study developed a methodology to fractionate soil carbon by degree of oxidation using potassium permanganate, distinguishing labile and non-labile carbon pools, and created a Carbon Management Index (CMI) combining pool and lability indices to assess agricultural sustainability. The CMI was validated across cereal, legume, and sugarcane systems in Australia and Brazil, demonstrating its utility in quantifying changes in soil carbon dynamics under different management practices.
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