Those of you that have followed The Garden Professors for some time know that Jeff Gillman and I are relentless in our pursuit of gardening myths to explode. Social media – Facebook in particular – seems to be a natural breeding ground for dumb and/or dangerous home remedies that go viral. Most of these have no basis in actual science and are easy to dismiss. Other recommendations may have some science behind them, but a careful review of the literature often shows that the bulk of research does not support that particular practice or product. These ones are trickier to deal with, and nothing has been trickier for either me or Jeff than compost tea.
The two of us have posted extensively on this topic in the last six years: just use the search function over in the left hand column of this blog and type in “compost tea”. You’ll find enough reading to keep you busy for a while. I summarized the state of the literature a few years ago in the now-defunct MasterGardener Magazine and to be honest the accumulated literature hasn’t changed much in terms of generating solid science supporting compost tea use. But its popularity seems to be increasing among landscape professionals and gardeners alike.
I get a lot of questions on compost tea from Master Gardeners in particular, who are bound by their positions as university volunteers to use science-based information. One of their major resources is the state university associated with their program – and recently this has become a problem for WSU Master Gardeners. Because on the Washington State University website you can find one professor who cites the lack of credible, consistent science on compost tea usage and another professor who provides workshops and webinars on making and using compost tea. Master Gardeners are understandably confused about what they can recommend and irritated that their university provides conflicting information. Why, they ask, does the university allow this to happen?
The answer is found in one of the most important values that universities protect: the academic freedom for faculty to speak their minds. Ideally this means that faculty can speak up about topics that are unpopular with university administrators without fear of reprisal, but it also means faculty have a soapbox on pretty much any topic they wish. And that’s whether or not they have any expertise or credibility on that topic. (For a particularly egregious example, one needs look no farther than prestigious MIT who has a research scientist with no expertise in biology or chemistry but who publishes articles in marginal journals linking glyphosate – the active ingredient in Roundup – to just about every known human malady.) Universities tend not step into this fray as it is a slippery slope – who decides what faculty speech should be censured and which should not?
How can Master Gardeners and others decide what information to believe? Well, that’s actually the mission of this blog and our Facebook page and group – to provide the best current gardening science and to help the public increase their scientific literacy skills. Science is not immutable – it advances as credible, published evidence accumulates. When and if compost tea ever becomes a consistent, effective product, we will be the first ones to share that information.
What about worm tea? Any reliable science on that?
Not substantial enough to deserve a blanket recommendation. There do appear to be some stimulatory effects of some vermicompost teas, but the data are too thin and inconsistent at this point.
Thanks. I’ll continue to use it on plants since it doesn’t sound like it’s detrimental anyway. Love the Garden Profs posts. It’s very valuable to have knowledgeable people sort through the gardening and horticultural information and let us know what is folklore and what is evidence-based.
I thought this post on academic freedom was especially interesting because it brings up a real cunundrum for universities. I can see how a university would be loath to censor a professor’s opinion because it is not in keeping with the mainstream thinking in a particular field of study. But you usually hear such arguments when the subject matter is in the social sciences or philosophy, for example — not the hard sciences where rigorous peer-reviewed studies and not opinion should be the criteria.
Even so, if you want to apply academic freedom to the sciences there has to be a distinction between what is currently accepted by the majority of scientists in a particular field, studied and peer-reviewed, and what is a variant or minority opinion or not properly supported.
I don’t think academic freedom is a good enough reason to allow the public release of questionable information under the auspices of a university. We want to believe — and we have a right to trust — that we are getting scientifically- based information from horticultural departments, or any other science department in a university. Not somebody’s scientifically-unsupported opinion or belief.
When a professor’s opinion conflicts with the best and most current data the university has on a particular subject, shouldn’t extension master gardeners as well as the rest of the public, be told that the opinions and conclusions drawn in this bulletin or report, or any such document released to the public, are not endorsed by the university’s plant science or horticulture department. Surely, some such statement could be appended to a paper with questionable views. To me, this would satisfy the academic freedom component of the equation — if that should even be applied to the sciences — while protecting the university’s credibility as a trustworthy source of information.
Here in the UK the remit of universities and horticultural colleges does not include gardening advice to the public so the issue of academic freedom does not arise in this field.
As a retired horticultural lecturer I feel that my own methods are unorthodox – albeit science and experience based, but would not go down well with my college if published in their name. I relish the opportunity to promote my ideas in my own name.
I do have a problem with this science based policy. Take bonemeal which I regard as total rubbish as a fertiliser and is a material that I would use never use. I find quite often on your Facebook site readers mentioning it in their questions about planting.
Personally I would say that it is a complete waste of time but just somewhere in some rare circumstance it might be useful?
I think the issue is what “hat” you are wearing when you make recommendations. As a private citizen (in your case retired) I think you have the latitude to recommend what you wish regardless of whether it’s scientifically supported or not. The only thing you are risking is your own reputation. But Master Gardeners are official agents of their sponsoring university, which is liable for anything they say or do. In that regard, the university does not want to risk a lawsuit and so insist that their volunteers only provide science-based information. It may be a sad sign of the times that they are more concerned with getting sued than having their volunteers use fact based information solely for its own worth, but so it goes.
Regarding bonemeal – sure, if there’s a demonstrated deficiency in phosphorus. Otherwise it’s nutrient overload with all the problems associated with phosphate toxicity.
Compost tea only works when applied at midnight on full moons that happen on Fridays.
Seriously though, I wonder what the significant difference is between worm compost and the not worm compost. If compost is the sum product of organic material passing through the digestive tract of living organisms what is the difference in it passing throught the digestive tract of a worm or only a bacteria, for example? And the bacteria, fungus would need to break the material down before the worm can slurp it up. Through the process of decomposition in a regular pile, the worms naturally appear. In the last couple of years vermicomposting has become such a big thing as if worms were just discovered and only added by secret smart people. What do you think?
The process of going through worm digestive tracts appears to add biochemicals to the finished compost that weren’t there before. Some of these can stimulate plant growth. There have been trials comparing regular compost and vermicompost that demonstrate these differences.