Biostimulant or Soil Improver: Which Label Fits Your Product?

Under EU Regulation 2019/1009, a soil improver works on the soil and a plant biostimulant works on the plant. Pick the category by the effect you want to print on the bag and can prove, not by what the product is made of, because the label may only claim the functions that passed conformity assessment.

The raw material does not decide the category. The claim does.

Two categories, two different promises

The regulation sorts EU fertilising products into seven product function categories, and two of them get confused all the time. Annex I defines a soil improver (PFC 3) as a product whose function is "to maintain, improve or protect" the physical or chemical properties, the structure or the biological activity of the soil. A plant biostimulant (PFC 6) is a product that stimulates plant nutrition processes independently of its own nutrient content, with the sole aim of improving nutrient use efficiency, tolerance to abiotic stress, quality traits, or the availability of confined nutrients in the soil or rhizosphere. You can read both definitions in Annex I of Regulation (EU) 2019/1009.

So a soil improver promises a better soil. A biostimulant promises a better-performing plant. The same humic-rich organic material could, in principle, be sold either way. What changes is the promise, the evidence behind it and the route to market.

What each category asks of you

An organic soil improver, PFC 3(A), is mostly a recipe test. At least 95% of the material must be of solely biological origin, it must contain 20% or more dry matter and at least 7.5% organic carbon by mass. Peat, leonardite and lignite are allowed; other fossilised material is not. The label then declares dry matter, pH, electrical conductivity, organic carbon, the minimum organic nitrogen with the origin of the organic matter, and the carbon to nitrogen ratio.

A plant biostimulant is an efficacy test. Annex I states that it "shall have the effects that are claimed on the label for the plants specified thereon". Under Annex III the label must give the effect claimed for each target plant, the application method and any instructions that affect efficacy, such as soil management or the fertiliser programme it is used with. That means trial data, crop by crop.

The rule that catches formulators out

Annex III, Part I, point 2 is the line to read twice. Where a product has functions from two or more categories, only the functions that went through a successful conformity assessment may be claimed with the category names. Point 8 adds that any other information must not mislead the user, for example by giving the product properties it does not have, and must relate to verifiable factors.

In practice this means a product registered as an organic soil improver cannot also tell growers it raises nutrient use efficiency. If that is your selling point, you need the biostimulant assessment and the evidence that goes with it. If you want both claims, the regulation offers a third route: a fertilising product blend (PFC 7), made of two or more EU fertilising products whose compliance has each been shown under its own procedure.

How to choose, in four questions

1. What will the grower buy it for: the soil, or the crop's response?

2. Which single sentence do you want on the label?

3. Do you have replicated trials, per crop, that support that sentence?

4. Do your distributors sell on soil structure and organic matter, or on fertiliser savings per hectare?

If the honest answers point to soil properties and you have no crop trials yet, PFC 3 is the faster, cleaner route. If your buyers pay for yield per kilogram of NPK, only PFC 6 lets you say so. For the wider market context, see Why a $5.8B Market Still Lacks a Complete Biostimulant.

How we made this choice

At Sapropel Organics we make HUMUSON from freshwater lake sapropel in the EU under Regulation 2019/1009, and we frame it as a plant biostimulant with a nutrient-use-efficiency function, because that is what our trials measure. Under tested conditions it can enable a 25-50% cut in the standard mineral NPK programme while keeping productivity. It does not replace the N, P and K a crop needs: on its own, without mineral fertiliser, it yielded clearly less.

The takeaway

Decide the category from the claim, then build the evidence for that claim. A soil improver sells a better soil; a biostimulant sells a measured plant response, and the label can only carry what passed assessment. Choosing first and proving later is how products get stuck.

If you formulate or distribute organic inputs and want to see how a lake-sediment biostimulant is documented, from the lab analysis to the trial reports, let's talk.

Related questions

Can a humic product be a soil improver? Yes, if it meets the PFC 3(A) composition limits and claims only soil effects.

Can one product claim both functions? Only the functions that passed conformity assessment, or as a PFC 7 blend of assessed components.

Does a biostimulant replace fertiliser? No. It works independently of its nutrient content and alongside a nutrient programme.

Sources

Regulation (EU) 2019/1009, Annex I: product function categories (legislation.gov.uk)

Regulation (EU) 2019/1009, Annex III: labelling requirements (legislation.gov.uk)