Biological “Soil health” is a highly complex issue. In broad terms, biologically active soils are

robust and resilient to change. Microbes produce complex arrays of metabolites, each species

contributing to, and interacting with a slightly different array of processes in soil. Moreover,

biologically active soil may confer a number of specific functions. These potentially include plant

growth enhancement, carbon sequestration, toxin degradation, mineral cycling and pathogen

suppression.

In the last three years methods to measure and quantify the soil biology via profiling of the

microbial community have changed dramatically. Previously, soil microbial diversity was

measured by inference using techniques which include direct counts, Fatty Acid Methyl Ester

(FAME) profiles, Biolog substrate utilisation, and biomass (see Schutter et al 2001). In more

recent studies, molecular DNA based measures of microbial diversity and community

composition have become more common. Molecular techniques too have their limitations and

analyses that include both molecular and other methods may provide a more holistic view of soil

biology and function.