How do I show the effect is not from nutrients?

If a product supplies nitrogen or other nutrients, plants may grow better simply because they receive more nutrition. That does not on its own demonstrate a biostimulant effect.

The evidence should explain why the result supports the particular effect you want to claim.

These are possible research comparisons, not a compulsory three-treatment plan. The specialist decides which comparisons are appropriate.

Give the trial provider reliable information about the product composition and intended use. The amount supplied during use matters, not only the concentration in the bottle.

This helps the specialist consider whether nutrition could explain the result.

For an illustrative calculation, a product containing 2% nitrogen by mass and applied at 5 kg per hectare supplies 0.1 kg of nitrogen per hectare in that application. Include later applications when considering total supply.

If your dose is in litres but the analysis is given by mass, you also need the product density. Keep nutrient forms and reporting units consistent.

This is arithmetic, not a nutrient limit or an acceptance threshold. Whether and how the trial comparison needs adjustment belongs in the specialist’s design.

EN 17700-1:2024 uses reference quantities per biostimulant application to determine when the control must receive an equivalent nutrient top-up. Compare the amount delivered at the tested dose, not the percentage printed on the bottle.

Selected examples are shown below in an original summary. The official standard also covers other nutrients; these three examples are not the full list.

If the product delivers more than the relevant reference, the control must receive an adequate equivalent amount in equivalent nutrient forms at each application. These are trial-control reference values, not legal maximum nutrient contents for a biostimulant.

For example, a soil-applied product containing 12% N at 100 kg/ha supplies 12 kg N/ha. That exceeds the 10 kg N/ha soil reference, so the control needs nutrient balancing. The earlier 2% N at 5 kg/ha example supplies 0.1 kg N/ha, below both N references. Being below a reference does not itself prove that the response is independent of nutrients.

The design should allow the effect of the product to be distinguished from differences in nutrient supply or growing conditions.

There is no single comparison to copy for every product. Ask your specialist how the proposed design addresses this question, and discuss it with the notified body.

An attractive result needs a clear explanation. Link the measurements to the claim rather than assuming that any increase in growth proves biostimulation.

If the evidence does not separate the effect from nutrition, more work may be needed before the claim can be supported.

The nutrient concentration is only part of the picture. Consider the dose, application frequency and route of use. Two products with similar nutrient concentrations can supply different amounts when used differently.

Make sure the composition information represents the product being tested. Give the provider information about both the product and the normal fertiliser programme.

Suppose a product contains nitrogen and the treated crop produces more biomass. Comparing it only with a crop that receives less nitrogen may leave two explanations: extra feeding or a biostimulant effect.

A specialist may consider a nutrient-matched comparison to investigate this. The form, availability and timing of nutrients can matter, so matching a total amount on paper is not always enough.

This illustrates the question to resolve, not a prescribed control treatment. The official standards contain the precise provisions for the approach used.

Yield or biomass shows a response, but does not by itself explain the cause. Measurements linked to the claimed effect can help build a clearer picture.

For a nutrient-use question, the amount supplied and taken up can be relevant. For a stress claim, evidence of the stress and plant response matters. Choose measurements before the trial rather than searching afterwards for an explanation that fits.

• Reporting nutrient concentration without considering the dose applied.
• Giving the comparison crop a different fertiliser programme without accounting for it.
• Assuming a small nutrient amount can never influence the response.
• Treating a higher yield as proof of every biostimulant claim.

A fair comparison reduces these doubts. It does not replace the rest of the product assessment.

The company doing the trials should be able to show that its staff are competent and that the work follows suitable quality criteria. Check this before commissioning the work.

Certification is not a blanket requirement for every biostimulant efficacy trial. Ask your notified body whether it requires a particular certification, accreditation or recognised quality scheme for your assessment. A certificate alone does not guarantee acceptance.

The EN 17700 series provides a recognised framework for evidence supporting plant biostimulant claims. Using standards is voluntary; the product must still meet the legal requirements.

This article combines original explanations with selected numerical and scope requirements from the standards. It is not a complete protocol or a substitute for the official standards and their full conditions. Agree the chosen approach with a qualified trial specialist and your notified body.