Earlier this week, Michael (thanks Michael for the question!) wrote in with an intriguing question. "Biodynamic Farming - based on principles originating with Rudolph Steiner a long time ago - purports to prime microbial health in various ways. I looked into this years ago and could never really validate whether the claims of its success are credible or not. It’s very ‘whoo-whoo’ in places, reflecting Steiner’s belief in mysticism, and so I’m inclined to write it off.... What do you think? Is biodynamic farming credible, and in what ways?"
For this blog post, I did my best to dig through the scientific literature on biodynamic farming. There is undeniably some mystical stuff going on with biodynamic farming. Like Michael, my first impression was to question what I was reading. And to back us up, there are definitely a host of expert scientists who are highly skeptical. To put it briefly, the researchers who authored this opinion piece describe biodynamic farming as "a practice that invokes cosmic forces to improve soil quality."
However, that is, after all, only an opinion piece, so I searched for some hard data, and I was able to find some. Most of it stems from one long-term trial, the "DOK" system comparison trial (bio-Dynamic, bio-Organic, and “Konventionell”) in Germany. This trial compared biodynamic, bio-organic, and conventional farming systems. It went on over decades (from what I understand it is still ongoing, with about 30 years of data at the moment), and resulted in a great host of peer reviewed publications.
As far as I can see, there is no scientific proof that invoking cosmic forces to improve soil quality has any concrete benefits. Actually, in order to test this, a study would have to compare traditional biodynamic farming with a farming method with all the 'hard' components of biodynamic farming (manure composting, organic fertilization, et cetera), but lacking any mysticism. I didn't find any studies that compared exactly that - although, please do let me know if you know of any - and also saw no convincing evidence that the 'woo woo' stuff was the stuff that made a difference.
What I did find, though, was that some biodynamic farming methods do actually seem to be beneficial for soil microbes in particular. Biodynamic farming and other forms of organic farming (again, termed "bio-organic" farming in the DOK trial literature) were pretty comparable in terms of plant health and yield but there was some difference in the microbial makeup.
For instance, in this Science paper from 2002, the authors actually did see that there was a higher amount of soil microbes in soil from biodynamic farms. Next best in terms of microbiological content was bio-organic farming, followed by conventional farming methods. In addition, there was both a higher amount and a higher diversity of microbial populations in biodynamic soils. This is interesting, because the amount of microbes alone does not per se correlate to a 'healthier' ecosystem. You can think of this just like ecosystems on the macro scale. For instance, just because there was an excess of bunnies at UVic in the 'noughties', that doesn't mean that the ecosystem was a healthy one. Rather, it is generally accepted that ecosystem diversity is a better approximation for ecosystem health. The analogous macro ecosystem might be one with bunnies, but also lots of different plants for the bunnies to eat and lots of different predators, like coyotes and eagles and owls, that would eat the bunnies and keep everything in balance.
Based on their analyses, the authors of that Science paper group biodynamic and other methods of organic farming together in their conclusion "that organically manured, legume-based crop rotations utilizing organic fertilizers from the farm itself are a realistic alternative to conventional farming systems". Having said that, as expected, there were also more 'unwanted' microbes like the protist Phytophtora infestans (that's the one that caused the Irish potato famine) in organic and biodynamic soils, and crop yields were lower than with conventional farming. But of course there are other downstream benefits (e.g. less fertilizer input needed in bioorganic and biodynamic farming versus conventional farming).
I also found a 2019 follow-up article from the same research group, published in Nature. There, they note that, "Even though considerable parts of Steiner’s biodynamic philosophy and practices lie beyond scientific judgement, a fair share of the available peer-reviewed research results from controlled field experiments as well as case studies show effects of biodynamic farming on yield, soil quality and soil biodiversity". But then, I did notice that they cite only their own papers; they all include Paul Mäder in the authorship list. I'll get back to that later.
Later in this Nature article, the authors argue that the main scientific difference between biodynamic and bioorganic farming likely comes down to the type of manure applied to fields. At biodynamic farms, the manure is composted, whereas "bio-organic" farming, by their definition, uses "rotted farmyard manure". They explain that applying composted manure may raise soil pH more than rotted manure, which could provide a better environment for soil microbes to flourish within. This is in line with findings from other researchers that have suggested that composting manure before applying it to fields increases soil microbiological content.
In the end, I would say that all that can be concluded from the available research is that composted manure (as used in biodynamic farming) is better than fresh manure for increasing the amount and diversity of microbes in soils. From what I can find, there is no evidence that biodynamic farming as an encompassing practice, with all its mysterious mystical and cosmic components, has any added value for 'soil vitality'. Based on the robust literature that I could find, I would argue that the main benefits of biodynamic farming seem to come down to the fact that it is a branch of organic farming - and benefits of organic farming to e.g. soil microbiological content and reduced negative environmental impacts are pretty well supported by science.
I'd like to end this piece with a few of my top tips for evaluating scientific writing. It can be difficult to dig through piles and piles of endless scientific manuscripts and evaluate which manuscripts present well-backed findings, and which are espousing questionable hypotheses, encased in scientific jargon to lend some academic-esque oomph to the words. Here are my top 3 tips for separating the pseudo from the science online:
Is there an academic consensus? Us lab-scientists often joke that if you set up a study right, you'll be able to show whatever data you want. The point is, we have to be very careful in designing a study to avoid introducing bias, and avoid pushing your results in a certain direction. As a result, one of the best ways to evaluate if a piece of science is good is to see if it has been replicated by other scientists. In other words, have other groups of scientists found the same thing? In terms of biodynamic farming, my spidey-senses tingled when I saw that the same author was present on all of the research papers that I found. Alone, this definitely does not mean that any of the conclusions in these papers were false or wrong in any way, but it did spur me to look for more articles from other researchers to be on the safe side. And in the end, that is why my conclusion from all of this reading is mainly in regard to composted manure being beneficial to soil microbes - because that is the bit of information that is also very clearly backed up by other groups of scientists.
Where is the money coming from? To be honest, I haven't done any serious financial tracking for this article, but this one is a good follow-up to the whole "avoiding bias when setting up a study" thing. The classic example of tracing the money in immunology is the Andrew Wakefield case. Wakefield, the "vaccines cause autism" guy, stood in a position to make loads of money if he could only show that the MMR vaccine was in some way dangerous. And so, he found a way to show it - and even though his so-called evidence was exceedingly shaky, he could phrase it in a sciency-enough sounding way that his results were published (though, later retracted) and are still out there in humanity's collective hive mind doing harm. To make matters worse, Wakefield also did not disclose his financial interests - he tried to hide them. To make a long story short, if a scientist stands to benefit heavily from skewing their results in a certain way, and they've not clearly disclosed that interest, it's best to keep a pinch of healthy skepticism regarding their results until they can be repeated by other, less biased scientists.
Legit science should be peer reviewed. Peer review is the practice of sending out scientific manuscripts to other experts in the field, who are charged with ensuring that, for instance, the experiments are set up properly, and that the eventual conclusions from the raw data make sense. I wrote more about peer review and my experience of it here if you're interested in finding out more.