What was it all about?

Herbicides are applied in most banana plantations to reduce competition with weeds. This project sought to understand what impact – if any – these herbicides have on soil health, through their influence on soil microorganisms.

There has been speculation that application of herbicides may impact on soil functions. In light of this, the researchers set out to quantify changes in soil biological communities following the application of registered herbicides, and to determine if there is potential for biological remediation of herbicides.

The project work has led to the production of a draft ‘herbicide risk tool’, which assesses the effect of the different herbicides available for use by the industry on different soil microbial communities. When available, the tool will assist growers to make decisions on which herbicides to use, given their specific circumstances with soil management.

In terms of results, investigations revealed that following single applications of registered herbicides, applied at recommended registered rates, there were only minimal and temporary impacts on soil microbial communities, while application above recommended rates led to greater reduction in soil biological functions.

There remain some questions about the effect of multiple applications, as only single applications of active ingredients in the herbicides were trialled in this project. Rotation of herbicide active ingredients, with a sufficient spell between applications, is likely to alter any potential impacts on soil organisms. This could be one strategy to manage herbicide impacts on soil biological functions, and reduce the risk of weed resistance to herbicides.