Biological test of soil health using molecular techniques: Final report

During the feasibility stage of the project, we were able to identify suitable primers for the most common earthworms found within each earthworm ecological group in New Zealand (e.g. Lumbricus rubellus as epigeic, Aporrectodea caliginosa as endogeic and Aporrectodea longa as anecic). The primers used could specifically identify target earthworm species using Real-Time PCR (RT-PCR).

Soil samples collected from five sites during the development stage of the project showed good correlation between molecular and morphological assessment (R2 0.907). The test also showed good extraction efficiency and precision, especially from dried and fine grind samples. Further samples analysed during the validation stage of the project reduced the strength of correlation between molecular and morphological assessment of earthworms (R2 0.193). Investigation into factors causing this are ongoing. However, the test was sensitive to changes in earthworm abundance at individual sites.

Further data needs to be collected prior to the test becoming commercially available to ensure confidence in the test developed, and the ability to predict earthworm abundance and diversity.

To use earthworms as indicators of soil biological health an assessment of both abundance and ecological diversity is required. The collection of further data to help assess whether the test is appropriate for commercial use will be ongoing in aligned research. Understanding factors that can cause variation in results is important for the development of a reliable test.