Soil Metagenomics: A Prescription for Soil Health?.

Few would dispute that microorganisms—and macro-organisms—are essential to the proper functioning (i.e., health) of a soil. Yet, there is little agreement about how to assess the life present in soil to determine if a given soil is healthy or not. To date, biological measures of soil health have been centered on biological functions, such as respiration or nitrogen mineralization. In part, this was because suitable measures of soil organisms did not exist or were known to have serious flaws; in part, the activity of soil organisms was viewed as more informative than knowing their abundance or variety. The first objection has been overcome through the development of numerous methods that provide quantitative and reproducible data on the abundance and taxonomic diversity of the soil microbial community, although we haven’t fully established relationships between these data and soil function and thus do not know how to interpret these data. For example, it is intuitive to think that a more diverse microbial community is better, but empirical evidence suggests that the functional redundancy of soil microbial communities is high, at least for many biological processes. The latest, “omics” techniques (e.g., metagenomics) hold promise of describing the functional potential of the soil microbial community, which might yield greater insight into the health of a soil than taxonomy-based metrics. It is unclear, however, if metagenomics data will provide greater predictive power than direct measures of biological activities.