This International Standard specifies a method for direct extraction of DNA from soil samples to analyse the global structure and the abundance of soil bacterial communities using PCR-based technologies. This method is mainly dedicated to agricultural and forest soils. This method can possibly not be suitable for soils rich in organic matter (e.g. peat soils) or soils heavily polluted with organic pollutants or heavy metals.

The direct extraction of DNA from soil samples provides unique insight into the richness and structure of microbial communities which are key parameters to estimate the biodiversity of soil microbiota. Molecular approaches based on PCR (polymerase chain reaction) amplification of soil DNA constitute a promising domain and can contribute in the near future to the development of routine tools to monitor the microbiota of soil environments.

Users of the method ought to be aware that although soil submitted to the DNA extraction procedure is sieved thoroughly (2 mm mesh, procedure described in 5.1), plant residues can still remain in soil samples and, as a result, traces of plant DNA can contaminate the soil DNA extract.