Fractions of soil organic matter (SOM) were obtained from three soils using alternative physical fractionation procedures, and evaluated against the requirements of model pools. The authors compared two-stage density fractionation (isolating free and intra-aggregate fractions, before and after dispersion, respectively) with particle size separation of dispersed soil. For full comparison, the organomineral fraction residual from density fractionation was also size separated. In standardizing the density-based method, the study found recovery of intra-aggregate organic matter highly sensitive to separation density as compared with the free. Recovery of the intra-aggregate was also influenced by dispersion energy.
In Rees, R.M., Ball, B.C., Campbell, C.D. and Watson, C.A. (eds) Sustainable management of soil organic matter, CAB International, UK., pp 90-95.