Using PCR For Soil Health Testing | Hill Laboratories - NZ


Using PCR For Soil Health Testing

Date: 9 Feb 2022
Author: Hill Laboratories

Late last year Hill Laboratories and AgResearch collaborated in a funding bid to the Our Land & Water National Science Challenge (Toitu te whenua, Toiora te wai) for a project to investigate whether earthworm DNA could be extracted from soil and measured as part of a soil health test.  The idea is to investigate the feasibility of soil DNA extraction and then quantification of earthworm species important in sustainable growing systems. The funding bid was successful, and our molecular biologists are already busy developing methods in partnership with Dr Nicole Schon and others from the AgResearch team at Lincoln.

The focus is on the three species of common NZ earthworm found in pastoral systems, being Aporrectodea caliginosa (top soil), Aporrectodea longa (deep burrowing) and Lumbricus rubellus (dung) and whether PCR technology can be used to quantify their presence in soil samples collected in a similar way to samples used for soil fertility tests. 

This is an exciting foray into the potential for a new soil biological health measure, which we know is of strong interest to our agriculture customers who are custodians of the whenua. Soil biological diversity is very large, and interpretation of biomarkers is quite complex due to the many environmental factors affecting populations of organisms. By focusing on earthworm abundance using molecular techniques in the first instance, the laboratory will learn about the effectiveness of DNA extraction from soil and its potential for measurement of other organisms in the future. 

The project is in the early feasibility stage, which is looking promising, but there is a lot more to do and we will be reporting progress as part of the funding requirements. In time, if PCR measurement of earthworm species abundance in soil indeed proves effective as a commercial test, it will be a useful addition to the existing Soil Health Profile currently on offer. The Soil Health profile includes all the usual soil fertility tests (pH, Olsen P, Cations and Sulphur) along with Organic Matter, Nitrogen and Hot Water Extractable Carbon. The Hot Water Extractable Carbon test has been shown by researchers to be a good (indirect) indicator of soil biological health due to its strong correlation with microbial biomass carbon.

The laboratory is very keen to expand into testing that utilises our skill and capacity with molecular biology techniques using RT-PCR (Real-Time Polymerase Chain Reaction). We have been using RT-PCR for some time now for testing Psa in kiwifruit leaf, food pathogens and more recently measuring SARS-CoV-2 (the virus responsible for Covid). Advances in DNA technologies are continuing, and it is part of Hill Laboratories innovative approach to make use of these wherever possible.