My favorite myth-busting horticultural educator, Linda Chalker-Scott, has just released a literature review of the available scientific knowledge behind biodynamics.
First, a modest introduction to biodynamics: Biodynamics is a growing method created by philosopher Rudolf Steiner in the 1920’s. While Steiner is to be praised for creating one of the first modern attempts at a sustainable agriculture system, he was neither trained in agriculture nor did he use any sort of scientific principles in coming up with his methods for aligning terrestrial and cosmic forces. These methods include stuffing dandelion flowers into the mesentery of a cow, burying it in the ground in winter and retrieving it in spring. While theoretically possible that there is some sort of beneficial enzymatic reaction between dandelions and cow entrails, Steiner came up with this method through clairvoyance and meditation instead of any sort of evidence or testing to see if it worked.
Advocates have added other principles to the system to create what is considered biodynamic agriculture today, and these principles are generally in line with organic agriculture, with the exception of Steiner’s special preparations. Some of the preparations have entered internet garden lore as home concoctions used in isolation. For example, the practice of blending up pests (not in MY blender, thank you) and spraying them on crops to theoretically deter the living members of that pest bears strong resemblance to Steiner’s methods of burning pests and scattering the ashes over crops.
Despite the mystical and decidedly non-scientific origins of biodynamics, there have been several decades of scientific inquiry into its effectiveness. Ms. Chalker-Scott reviews the available evidence and summarizes it in The Science Behind Biodynamic Preparations: A Literature Review, in the December 2013 issue of HortTechnology. The article, although scientific in nature, is accessible and understandable to the average garden reader. It is recommended reading for anyone considering the use of these methods.
She summarizes that most of the available research comes from poorly constructed or inconclusive studies, and that biodynamic plots do not outperform organic plots, although both outperform conventional agriculture in terms of soil health and sustainability.
To date, there are no clear, consistent, or conclusive effects of biodynamic preparations on organically managed systems… Given the thinness of the scientific literature and the lack of clear data supporting the efficacy of biodynamic preparations, biodynamic agriculture is not measurably distinct from organic agriculture and should not be recommended as a science-based practice at this time.
However, that means we can also reverse that: there also appears to no measurable negative effects. If you are drawn to biodynamics for philosophical or faith reasons, science does not have evidence to suggest that you should not do them.