Testing biostimulants for validating the claims: a multi-level analysis

Plant biostimulants are placed on the market on the basis of their intended effects on crop plants, referred to as ‘claims’. In the EU, standardized protocols will be required to validate the claims of biostimulant products to access the EU market, but which protocols will prove be efficient, robust and applicable to a range of crops still needs to be determined. Although many data are available, from the laboratory to the field, it seems important to generate parallel data sets by using the same biostimulants in the laboratory, in the greenhouse and in the field. By combining the data sets, the value of the different tests and the efficacy of the field and contained use approaches can be best evaluated. In order to set up an evaluation platform for biostimulants in Belgium, a project, named BioStimTest, has been initiated with the support of the Walloon Region of Belgium and coordinated by the company Redebel. Organic, inorganic and microbial biostimulant products, as available on the market, are being tested on winter wheat, maize and potato with field trials. Laboratory bioassays on model plants, seed germination tests, measurements of biomass and root development in hydroponic cultures, biomass and physiological measurements of greenhouse-grown plants are all used to compare these data with plant performance in the field. Improvement of nitrogen use efficiency and of drought tolerance are the two biostimulant claims considered by the project. Accordingly, different fertilization regimes and the limitation of the rain supplies by controlled rainout shelters are used in the field experiments, under the temperate climate of Belgium.