SETAC Spotlight: Biostimulants: a complex ecotoxicological challenge

There is evidence that biostimulant products can benefit arable and field grown horticultural crops, however, there are large knowledge gaps regarding the environmental safety and ecotoxicology of these products. Few studies look at the potential ecotoxicological effects of biostimulants, and those that do tend to focus on the individual component(s) of these products. 

Whilst acute exposure data, to individual biostimulant components, are generally above the Environmental Hazard Classification threshold of 1 mg/L, there is evidence of sub-lethal, long-term chronic effects. There are instances of toxicity at high and sustained application levels, which is of concern when there are no product usage regulations in place. Several biostimulant categories have exhibited indirect toxicity effects, e.g., increased bioavailability of metals and other bound toxins. Many biostimulants also have pesticidal properties, useful with regards to the dual action of plant growth promotion and crop protection, yet a concern that the non-selectivity of any pesticidal effects could be detrimental to non-target species. Similarly, the use of products that contain growth promoting bacteria will arguably influence the existing natural community composition, structure and function. 

Here we discuss the challenges involved in assessing the risk of biostimulant products to the environment. Where environmental risk assessments for products, such as plant protection products (PPPs), can base their decision-making process on a single active ingredient, biostimulant products are made up of various components, in highly variable compositions, with additional interactive effects, that all need to be considered to accurately assess any adverse impact they may have on the environment.  

Standard risk assessment approaches, on a product-by-product basis, would provide a clear measure of the ecotoxicologal impacts of a given biostimulant product, and if they are greater or less than the given application rates or predicted exposure concentrations following application. However, indirect toxicity, such as additive or synergistic effects of other contaminants present in the system, and the use of other products that are likely to be applied alongside biostimulants in real-world scenarios, also need consideration. 

If you would like to discuss any of the topics raised in this article, feel free to contact us.

The poster is available for free download.

The full report on which this poster is based is also available online for free download, part of the Defra-funded project entitled ‘Creating an Enabling Regulatory Environment for Enhanced Efficiency Fertilisers – NM0102‘.

You can find all of the other posters that CEA presented at SETAC Dublin here. You can also find all of our publications from previous conferences and links to journal articles we have authored on our library page.

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