How many trials do I need for a plant biostimulant claim?

EU CE marking is not the same as national registration. Under the Fertilising Products Regulation, you build evidence that the product meets the rules and complete its conformity assessment. Trial evidence is only part of that work.

If you sell under national rules instead, the country may have different evidence requirements. First decide which route you are taking.

EN 17700-1:2024 gives different minimum numbers according to the crops covered by a claim. The following is an original summary of the numerical requirements, not a copy of the standard’s tables.

The three groups broadly cover broadacre crops; woody perennial crops; and vegetables, ornamental plants, and aromatic and medicinal plants. Check the official crop grouping when planning your programme.

These are minimums for supporting a particular claim, not a guarantee of acceptance. The effect must be demonstrated for the relevant crop coverage, using consistent trial methods. Trials may take place in the same year or across different years. Simply completing the number of trials is not enough.

A series brings together independent field trials on the same crop, using a common objective, protocol and measurements so that the results can be assessed together.

For series analysis, EN 17700-1:2024 requires at least 4 trials, or at least 15 strip trials. A series is therefore not a single trial. Trials under controlled conditions are excluded from this field-trial-series approach.

For example, the minimum of 2 series for one whole crop group means one series on each of at least 2 crops. Using the 4-trial option, that means at least 8 independent trials in total. This is a different approach from the 6 individual-trial minimum; the two routes are not interchangeable just because the totals look similar.

A claim for one crop is narrower than a claim for many crops. Evidence from one crop or one set of conditions does not automatically support every intended use.

Write down the effect, crops and uses you want on the label. That gives your trial specialist a clear starting point.

Crops respond differently across places, seasons and growing conditions. A promising result at one site may not tell the whole story.

A programme of trials helps show whether the effect is consistent and how far the conclusion can reasonably extend.

As a counting example, imagine three independent trials, each containing four repeated plots for a treatment. That is three trials, not twelve. The repeated plots help describe variation inside each trial.

These numbers only illustrate the distinction. They are not a recommended programme or a statement of the standard’s minimum requirements.

For claims about making confined nutrients available in soil, a soil-only approach has its own minimums. The crop-group numbers above do not apply to this approach.

This summarises the counts in EN 17700-1:2024. Soil selection and the way results support a wider claim follow the provisions in EN 17700-5:2024. Do not choose arbitrary soils or assume that any six soil tests will qualify. Ask your specialist to confirm the suitable combinations.

Ask what existing results can contribute and what gaps remain. The right programme depends on the claim and the quality of the evidence, not just on reaching a number.

Discuss it with the notified body early. This helps avoid buying trials that do not answer the assessment question.

Start with the breadth of the claim. A named crop and a defined use give a more focused question than a claim for several crop groups and different growing conditions.

Then consider how variable the response is likely to be. Weather, soil, crop variety and management can all affect a result. A programme should give a meaningful picture of the uses you want to cover, rather than many similar tests in one convenient setting.

Separate product effects also need separate support. A programme planned for drought tolerance may not answer a question about fruit quality.

Suppose your first results suggest better nitrogen use in wheat. A focused programme would investigate that effect in wheat under relevant nutrient conditions.

If you want the label to cover wheat, tomatoes and fruit trees, the same wheat results do not automatically answer all those questions. You need to discuss how the evidence can support the wider scope.

This is an illustration of planning, not a prescribed trial programme or a statement of the standard’s minimum numbers.

A useful quotation separates the number of independent trials from the repeats within each trial. It also explains the crops, sites, growing conditions, measurements and reporting included.

Ask what happens if the intended stress does not occur or a trial cannot be completed. Agree access to the underlying data, not only a final summary.

Ask which route the quotation uses: individual trials, trial series or soil-only trials. Check that the proposed number and crop or soil coverage match that route. Use the official standards for the full design and assessment conditions.

• Choosing a trial package before deciding the label claim.
• Counting repeated plots as separate independent trials.
• Assuming one successful location represents every intended use.
• Buying extra trials without checking which evidence gap they fill.

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.

The numbers here are a planning summary from EN 17700-1:2024, not a complete trial protocol. The official standards contain the design, quality and assessment conditions that go with them. Agree the chosen approach with a qualified trial specialist and your notified body.