BBC LABORATORIES
Agricultural & Environmental Microbiological Services
Microbial Diversity Guide for Compost and Soil
What is species richness diversity (SRD)?
Species richness is a measurement of diversity that indicates the number of different species or different types of microorganisms that are present in a sample. The SRD determination of microorganisms in a particular microbial functional group is an index of the variety of microbes in that functional group. This index is derived from a standard microbial ecology formula that weighs the variety of species within a functional group from a normalized analysis of species richness against the total number of microorganisms associated with that functional group.
Why is diversity important?
In soil or compost, high species richness diversity promotes numerous interspecies relationships and interpopulation interactions. Species richness diversity is important because it allows for a more varied and flexible response to environmental fluctuations and stress. For instance, those communities with more diverse microbial populations will be more likely to cope with disturbances and stress than those communities with low diversities.
How can diversity information be used?
This index can be compared to other samples from a similar matrix (soil, compost, or liquid) and can be used to determine the impact of various crop management and agricultural practices on microbial diversity or to compare and evaluate different microbial products. In addition to the individual SRD determinations for various functional groups, an index for the total species richness diversity (SRDT) is a useful tool for the comparison of similar samples. This index found at the bottom line of the analysis sheet is the sum of the six individual SRD's for the sample.
| SRDT Index for SOIL | Classification | SRDT Index for COMPOST |
|---|---|---|
| > 12.5 | High Diversity | > 6.5 |
| 7.0-12.5 | Moderate Diversity | 3.0-6.5 |
| < 7.0 | Low Diversity | < 3.0 |
| Parameter | Species Richness Diversity Index SOIL | Species Richness Diversity Index COMPOST |
|---|---|---|
| Heterotrophic Plate Count (Aerobic) | 2.9 | 1.6 |
| Anaerobic Bacteria | 1.9 | 0.8 |
| Yeasts and Molds | 2.3 | 0.8 |
| Actinomycetes | 1.2 | 0.9 |
| Pseudomonads | 1.2 | 0.5 |
| Nitrogen-Fixing Bacteria | 0.7 | 0.3 |
| Total Species Richness Diversity Index (SRDT) | 10.2 | 4.9 |