Technique
BD Preparations
Nine numbered biodynamic preparations (500–508) made from cow manure, silica, and six medicinal plants, applied in tiny doses to soil and vines on a fixed schedule.
The preparations are the part of biodynamics that sounds strangest to a first-time reader and matters most to a certified producer. There are nine of them, numbered 500 through 508 in Steiner’s 1924 Agriculture Course. Two go on the soil and vines directly. Seven go into the compost pile.
What each preparation is
Preparation 500, horn manure. Cow manure packed into a cow horn, buried over winter, dug up in spring, and stirred in water for an hour before spraying. Applied to the soil to stimulate microbial life and root growth.
Preparation 501, horn silica. Finely ground quartz packed into a horn, buried through summer, and sprayed on the canopy in tiny quantities to enhance light absorption and ripening.
Preparations 502 to 507. Six compost preparations made from yarrow flowers, chamomile flowers, stinging nettle, oak bark, dandelion flowers, and valerian juice. Each one goes through a specific preservation step before it lands in the compost: a stag bladder, a cow intestine, peat, a deer skull, and so on. The doses are tiny. A few grams of each preparation seasons a compost heap that will feed a vineyard for a year.
Preparation 508, horsetail tea. Equisetum arvense, brewed and sprayed as a fungal control, particularly against mildew pressure.
The doses are very small
This is the point most newcomers miss. A vineyard does not flood its rows with horn manure. The standard application of preparation 500 is around three hundred grams per hectare, stirred for an hour in water and sprayed late in the day. The quartz in 501 is applied in even smaller quantities, often four grams per hectare. The framing biodynamic practitioners use is biological trigger, not fertiliser.
This is also why critics call the preparations homeopathic. The dilutions are so high that no chemical effect is plausible by mainstream measurement.
What the evidence actually shows
There is no peer-reviewed study showing that a buried cow horn changes wine quality in a blind tasting. There are several controlled studies showing that biodynamically farmed vineyards have measurably higher microbial diversity, better aggregate stability in the soil, and stronger vine root systems than conventional comparators on the same site. Stephen Brook has written about this gap in Decanter. Jancis Robinson takes the same line: the field-level outcomes are real and visible, the mechanism is not.
A working theory among soil scientists is that the preparations function as microbial inoculants. The buried-horn step incubates a specific community of bacteria and fungi that survive the stirring and spraying process. If that hypothesis holds, the preparations are biology rather than cosmology. Steiner’s framing was different, but the outcome would still be measurable.
Why producers keep doing it
Nicolas Joly has been the most public English-language voice on this question for forty years. His argument in Wine from Sky to Earth is that the preparations are not optional add-ons. They are the system. Skip them and you have organic farming, not biodynamics. Domaines like Leflaive, Zind-Humbrecht, and Nikolaihof all apply the full set on a documented schedule because Demeter certification requires it, and because they believe the wines show the difference.