What are biodynamic preparations? Explanation, making, effect, criticism

Biodynamic preparations are a set of nine substances made to Rudolf Steiner's recipes from mineral, plant and animal materials and applied in very small, highly diluted amounts to soil, compost and plant. They are the heart of biodynamic farming and the one feature that sets it apart from every other way of growing. For Demeter farms their use is mandatory. This article explains what the preparations are, how they are made and applied, what research says about them — and where the criticism of them has a justified core.

Preparations do not fertilise — they enliven

The most common mistake is to think of the preparations as a kind of fertiliser. They are not. They supply no significant amounts of nutrients: a few hundred grams of horn manure or just a few grams of horn silica are enough for a whole hectare. An amount like that cannot feed a plant.

Their task is a different one. The preparations are meant to guide and order processes — enliven the soil, steer the decomposition of compost, lead the growth and ripening of the plant. Steiner did not understand good manuring as a supply of substance but as "making the earth alive": the soil should become living so that the root does not reach into dead earth. The preparations set this aliveness in motion; the actual nutrient cycle is still carried by the compost and manure economy of the farm organism. Steiner accordingly called the preparations an "extra manuring" that "substantially enhances" normal manuring — not a replacement for it.

Because they work in such small amounts, their use is often compared with homeopathy. The comparison captures the point of the tiny dose, but should not be misread as an explained principle of action: how exactly such a small amount has an effect is precisely the open question — more on that below.

Eight or nine — the canon 500 to 508

The canon of preparations comprises nine numbers, which fall into three groups.

The two field spray preparations are stirred in water and sprayed. Horn manure (500), made from cow manure in a cow horn, works through soil and root and is applied to the soil in the evening. Horn silica (501), made from very finely ground quartz in a cow horn, works through light and ripening and is sprayed onto the plant in the morning. Steiner described them as a complementary pair: one "pushes up from below", the other "pulls from above".

The six compost preparations (502–507) do not go onto the field but into compost and farmyard manure, where they steer decomposition: yarrow (502), chamomile (503), stinging nettle (504), oak bark (505), dandelion (506) and valerian (507). They work as an ensemble and are usually used together.

Then there is the horsetail preparation (508), sprayed as a tea or decoction against fungal pressure. It has a special position and in the narrow sense is not a preparation but a plant care agent — which is why the tradition speaks of "eight or nine" preparations.

Ehrenfried Pfeiffer described the division of labour as early as 1938: horn manure (500) promotes root growth, horn silica (501) the capacity for assimilation, the compost preparations (502–507) strengthen the plants in their growth, with the stinging nettle (504) acting particularly on the quality of taste. It is this interplay, not the single preparation, that is meant to set the farm "in motion".

How are the preparations made?

Each preparation is made to a fixed recipe centred on an animal or plant sheath and a particular season. For horn manure, cow manure is filled into a cow horn and buried in the soil over winter; for horn silica, ground quartz goes into the horn and into the earth over summer. The solid compost preparations are filled into their respective sheaths — yarrow into a stag's bladder, chamomile into cattle intestine, oak bark into the skull of a domestic animal, dandelion into cattle mesentery — and likewise entrusted to the soil for a season. Stinging nettle matures without a sheath, surrounded only by earth, for a whole year; valerian is prepared as fermented flower juice.

The detailed practice of making them, authoritative to this day, was worked out not by Steiner himself but by later authors, above all Eckard von Wistinghausen, Pierre Masson and Walter Stappung. Anyone who wants to make them can find the detailed recipes in the portraits of the individual preparations and in this specialist literature — setting them out in full here would go beyond the scope and touch on the copyright of those works.

Application and the Demeter requirement

Before application, the field spray preparations are stirred rhythmically in water for an hour — dynamisation. A vortex is created, abruptly reversed and brought into chaos, again and again, until the preparation has passed its qualities on to the water. Spraying then follows promptly, because the effect of the stirred preparation fades after about a day. The compost preparations are placed as small lumps into holes bored into the compost heap, and the liquid valerian is poured over it; one set is enough for about ten cubic metres of manure.

For Demeter farms this is not optional. Horn manure must be applied at least once a year on all areas, horn silica as suits the crop, and the compost preparations belong in all organic farmyard manures. It is exactly this binding work with the preparations that distinguishes Demeter from all other organic associations — Bioland, Naturland or EU organic have nothing comparable.

Origin: the Agriculture Course of 1924

All preparations go back to Rudolf Steiner and his Agriculture Course (GA 327), which he gave to farmers in Koberwitz in 1924. Steiner gave the recipes and their rationale there, but explicitly meant them as a stimulus for independent research, not as a rigid recipe. The preparations are thus part of a larger idea: to run the farm as a living organism that is as closed as possible and largely sustains itself. The first preparations were made during Steiner's lifetime; since then the method has spread all over the world.

How do the preparations work? What research shows

Honesty is called for here, and it requires a distinction between two levels.

The biodynamic farming system as a whole — closed cycle, compost economy, no synthetic inputs — is well studied. The most important evidence is the DOK long-term trial of the Research Institute of Organic Agriculture (FiBL), which since 1978 has compared biodynamic, bio-organic and conventional farming on the same field in Therwil, Switzerland. The biodynamic system performs best on soil fertility: the organic soils show around 16 per cent higher humus content and up to 83 per cent higher activity of soil organisms than the conventional ones — with a moderate yield gap and far lower use of inputs. That a living cycle with good compost management benefits the soil is therefore measurable, not mere conviction.

It becomes harder with the isolated effect of the single preparation at its high dilution. Here there are indications but no closed chain of evidence. A study published in ISME Communications in 2024 by the working group around Jürgen Fritz (University of Kassel, 254 soil samples from Germany and France) reports that biodynamically managed soils contain more presumably growth-promoting microorganisms than soils that are only organically managed; the researchers interpret the preparations as a microbial "inoculation". Important for context: this is a comparison of biodynamic versus organic and a function predicted by calculation, not measured in yield — concluding from a local microbiome finding to soil fertility across whole fields is not supported, and the effects vary from year to year. Individual older field studies also report positive effects on squash, potato or Burgundy vineyard soils — small, heterogeneous and not consistently reproducible.

The researcher Hartmut Spiess therefore describes the effect of the preparations as "system regulation": balancing, hard to pin to a single measurement and strongly dependent on site, weather and management. An earlier research review (Brock and others, 2019) confirms this picture — a lot of research activity, some robust findings on the system, but no simple proof of effect for the single preparation.

The criticism — and its justified core

Critics call biodynamics esoteric because of its anthroposophical foundation. That is accurate insofar as central justifications do come from Steiner's spiritual science and not from empirical research: the talk of "cosmic forces", the role of cow horn and stag's bladder, the effect of certain constellations — none of this can be derived scientifically. Ignoring that makes things too easy.

Conversely, it would be just as unfair to conclude that the whole system is ineffective. The system's advantages for soil fertility and humus are documented, and there are now serious, if variable, findings on the microbiome effect of the spray preparations too. An honest approach therefore separates what can be documented from what is worldview, instead of condemning wholesale or exaggerating. What can be documented can be documented; what is biodynamic tradition or a Steiner concept should be named as such. Promises of healing or miracles do not do the preparations justice — and are not needed at all.

Frequently asked questions

How many biodynamic preparations are there?

Nine, numbered 500 to 508: two field spray preparations (horn manure 500, horn silica 501), six compost preparations (502–507) and the horsetail preparation (508), which has a special role.

Are biodynamic preparations the same as homeopathy?

No. They are applied in very small amounts, which suggests the comparison, but they do not follow homeopathic teaching. The comparison describes the small dose, not a proven principle of action.

Do the preparations replace fertiliser?

No. Steiner called them an "extra manuring" that complements and enlivens normal manuring with dung and compost but does not replace it. The nutrient cycle is still carried by farmyard manure.

Are the preparations mandatory under Demeter?

Yes. Making and applying them is a binding biodynamic practice and required of every Demeter farm. That is the decisive difference from other organic associations.

Do the preparations really work?

For the biodynamic system as a whole there is good evidence of higher soil fertility and humus content. The specific effect of the single preparation at high dilution, by contrast, is not conclusively proven — there are indications but no closed proof.

Conclusion

Biodynamic preparations are neither fertiliser nor miracle cure, but tools meant to enliven and order soil, compost and plant — and they are binding for every Demeter farm. Their value shows in their interplay and at the level of the whole system, whose benefits for soil fertility are documented. If you want to go deeper, each individual preparation has its own portrait with making and application.