Compost tea – now part of landscape design?

I spent yesterday at the Washington APLD meeting in Seattle (that’s the Association of Professional Landscape Designers) – a new venue for me.  In my relatively short time frame I focused on one example of an unsustainable practice (overamendment of soils with organic matter) and an unsubstantiated product (compost tea), both of which I knew were of interest to this group.  I came away with a lot of new colleagues and a shared sense of excitement that landscape designers, like other horticulture professionals, also want the best science on which to base their recommendations.

Imagine my frustation, then, when I was sent the national APLD “Guide to Sustainable Soils.”  Most of this document is very good – lots of information and graphics from the USDA and other reliable resources.  But scroll down to page 5, under the section “Soil Additives.”  And yes, there it is, compost tea.  Acccording to the APLD member who sent me this (not a Washington state member, by the way), the advisory committees that write these guidelines include people who make money from selling compost tea.  Surprised, no.  Disappointed, yes.

And it’s not just in landscape design.  Compost tea is ending up in specifications for landscape management contracts.  Reputable companies have to decide whether to hold their noses and apply useless products to secure contracts, or to not compete for the contracts at all.  In this economy, there aren’t many people who can afford to live on principle rather than a paycheck.

Compost tea is marketed, very effectively, through targeting emotional response.  We’ve already got science on our side, so here’s my suggestion to those of you who fight the compost tea battle:  start a little emotional targeting yourself:

  • Refer to compost as “slow food” for the soil system, as opposed to the liquid “fast food” tea that needs frequent application.
  • Suggest that Mother Nature’s been making tea herself for eons, letting rainwater perk through the compost.  Are we smarter than nature?
  • Point out that using compost is a natural, environmentally friendly approach to caring for the soil, rather than the big business, energy- and resource-consuming compost tea industrial complex that’s exploded in that last decade.

Over the top?  Probably.  But accurate?  Absolutely.

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Linda Chalker-Scott

Dr. Linda Chalker-Scott has a Ph.D. in Horticulture from Oregon State University and is an ISA certified arborist and an ASCA consulting arborist. She is WSU’s Extension Urban Horticulturist and a Professor in the Department of Horticulture, and holds two affiliate associate professor positions at University of Washington. She conducts research in applied plant and soil sciences, publishing the results in scientific articles and university Extension fact sheets. Linda also is the award-winning author of five books: the horticultural myth-busting The Informed Gardener (2008) and The Informed Gardener Blooms Again (2010) from the University of Washington Press and Sustainable Landscapes and Gardens: Good Science – Practical Application (2009) from GFG Publishing, Inc., and How Plants Work: The Science Behind the Amazing Things Plants Do from Timber Press (2015). Her latest effort is an update of Art Kruckeberg’s Gardening with Native Plants of the Pacific Northwest from UW Press (2019). In 2018 Linda was featured in a video series – The Science of Gardening – produced by The Great Courses. She also is one of the Garden Professors – a group of academic colleagues who educate and entertain through their blog and Facebook pages. Linda’s contribution to gardeners was recognized in 2017 by the Association for Garden Communicators as the first recipient of their Cynthia Westcott Scientific Writing Award. "The Garden Professors" Facebook page - "The Garden Professors" Facebook group - Books:

58 thoughts on “Compost tea – now part of landscape design?”

  1. I like this idea. Adding to the list, “Don’t dilute your compost with water – use the full strength real thing directly!”

  2. The bro
    chure certainly should say Aerobic Compost Tea (ACT) — This is the growth of beneficial micro-organisms from healthy and biologically diverse compost in an aerobic and well-fed environment in order to create an (admittedly perishable), easily portable, biologically verifiable, easily spread elixir teaming with beneficial microbial activity, ready to eat up the throughtfully-selected organic matter recently added to the soil, as well as the copious natural mulch placed on top of the newly planted beds. A healthy 5 gal. bucket of ACT covers the same amount of garden as several yards of compost. That sounds like a smart choice to me!

  3. Pamela, while it may *sound* like a smart choice, it’s not backed up with published soil science. People can believe whatever they like, but I’m hoping most professionals, like APLD members, would like to maintain their credibility with clients.

  4. Linda,

    Have you ever considered that there are some of us in the ACT industry that are not just out to make a quick buck? There are many charlatans and snake oil salesmen selling poor soils as compost to unknowing gardeners. Let’s not make generalizations that may not be accurate.

    I would agree that there is not enough science out there in regards to studies on ACT. I was disappointed with the studies in your peer review, in that many of them did not use proper methodology (measuring dissolved oxygen throughout the entire brewing cycle, good machine design, biologically tested compost, direct microscopy, etc..). To me, those studies show nothing more than a lack of understanding of scientific method on the part of the researcher, rather than “science” proving that ACT doesn’t work.

    I’m not claiming ACT is a silver bullet, nor that it is needed in every instance. I don’t make false claims regarding it’s ability to control disease (I find this to be more dependent upon environmental conditions and disease pressures). I think the main benefit of compost tea is the ability to increase nutrient cycling.

    So in your professional opinion, what is happening to the millions of bacteria, archea, fungal hyphae, flagellates, naked amoeba, and ciliates that are in a properly made ACT when they get added to the soil?

    Now unfortunately I don’t have the money or resources to conduct a University Study. Those of us that are credible do as much research and testing as we can (I do a lot of direct microscopy in-house on our composts and ACT). We are barely surviving as a company and hardly getting rich.

    I’m disappointed that you would allow comments like the one from Jimbo or Ray, as they show a lack of understanding of ACT, but then reply back to the supporter of the technology. Water does not “dilute” or “drown” soil microbes (with the exception maybe of nematodes), but in properly made ACT will increase the above sets of organisms exponentially in a given brewing period. That point can’t be argued because it can by physically verified with direct microscopy.

    I can tell you from having run a business selling ACT machines for the past 10 years that many people are getting results. There is beginning to be more research to support the technology. I know Elaine has a list of studies she likes to share to refute your list of studies, but I’m not here to get into that. Harvard University did a study a few years back on their grounds that incorporated compost tea into their lawn management. The University of Arizona is the process of finishing up an initial examination of it’s benefits on their grounds and are expanding the program based on their results.

    I’m not asking you to start accepting compost tea, but rather just be open-minded to the concept that there are people in the industry working hard to get more science to support the technology. We are not all out get rich, but rather to come up with responsible and environmentally friendly ways to improve our gardening practices.

  5. While compost tea from steeping compost in still water, i.e. exposing the compost to an anaerobic environment, obviously don’t contain aerobic migroorganisms, I still question the efficacy of aerated compost tea. Aerating the tea will breath life into an anaerobic mix, or brewing under aerobic conditions will result in more aerobic life, but as soon as you turn off the pump, conditions are immediately hostile to aerobic life. This is the way I’ve always seen it, perhaps it’s wrong so I’d love to hear from Linda if this is in some way biologically accurate.
    Another issue with the ACT process is that power, often coal-fired, is used to power them, rendering a carbon reducing product (home compost) to a carbon positive one, just as it would be if it were sent to landfill. You cancel out the good of home composting by making an aerated tea with it. So in essence you consume energy to create a product that isn’t proven to have any effect on soil health or plant growth. Applying compost to soils in its raw form is much easier, uses no energy (apart from your effort), and is proven to have benefits on both plant and soil health. It’s a no-brainer.

  6. Tad, I’d love to see such a list of supporting studies, because I sure can’t find them. I collect all the published scientific studies out there on this topic, as does Jeff Gillman. There are very few on nutrient cycling. Here’s a recent one published in Arboriculture and Urban Forestry November 2011 (Laboratory Assays on the Effects of Aerated Compost Tea
    and Fertilization on Biochemical Properties and
    Denitrification in A Silt Loam and Bt Clay Loam Soils, 37(6): 269–277).
    I was one of the reviewers of this paper, so I’ve spent a lot of time going over the data. Dilute compost tea was no different than water in terms of influencing nutrient content. Concentrated compost tea had minor effects compared to water. It seems much of the positive effect of compost tea in this experiment was due to water – not what was dissolved in it. The authors state that future research compare ACT to compost, which would be most enlightening. Look at the differences in this current study in terms of microbial content. “The compost contained 11,648 μg bacteria g-1, 3,547 μg fungi g-1 (mean hyphae diameter of 2.8 μm), 18,883 flagellates g-1,
    14,596 amoebae g-1, 11,338 ciliates g-1, and 1.2 nematodes g-1
    (analyses performed by Soil Foodweb, Inc., Corvallis, Oregon, U.S.)…On average (12 brews over 2008 and 2010 under similar conditions described), the ACT contained only a fraction of what was in the compost itself: 1,972 μg bacteria
    g-1, 4.9 μg fungi g-1 (mean hyphae diameter of 2.6 μm),
    1,920 flagellates g-1, 1,392 amoebae g-1, 7.7 ciliates g-1, and 0.1 nematodes g-1.” In case you’re curious, the compost and brewing kit used for this study were obtained from your company (KIS, Inc.).
    You can quibble about techniques in brewing, but if something is so difficult to do properly (in this case, brewing the perfect compost tea), how could you ever expect the typical home gardener to succeed?

  7. Hi Tad, you make some excellent points, and I agree that scientists can’t dismiss compost tea out of hand. We don’t filter comments except in extreme circumstances. You asked what happens to all those great compost tea organisms when you apply them — in my professional opinion (I don’t have data to back it up and I don’t want to claim that I do – so all I have is an informed opinion which you can accept or dismiss)– what happens is that, if the soil is good, the organisms in the compost tea are swamped by all of the other organisms in the soil and end up being just a drop in the bucket. In a poor soil I wo
    uld expect that the microorganisms would die — same as what would happen if we dumped a bunch of people into the middle of the Sahara desert. In all cases where compost tea is used I would suspect that compost would be a better amendment. One other thing which bugs me a little — Elaine Ingham, the woman who I see as most responsible for promoting compost tea — doesn’t have a refereed article on the topic. She’s no stranger to peer reviewed journal articles — she’s authored or co-authored quite a number — so why can’t she get something published showing how valuable this stuff is? I don’t get it.

  8. Linda,

    I agree with what you and your supporters herein have to say about compost. It is a vastly superior way to garden if one has enough compost to cover the area being cultivated. I’m pretty sure you are not going to deny that compost works mostly via the microbial nutrient loop (Clarholm, Bonkowski, Griffiths, Coleman, Torsvik, etc. etc.)
    One of the attributes, I’ve found of using compost tea is that if I’m low on [vermi]compost then I can use a fraction of my [vermi]compost (VC) to benefit a given garden area. This was particularly beneficial on our farm which we left two years ago. Rather than using several tons of VC over our cultivated area we could make a tank of ACT using a tractor bucket full. Of course we verified that it was ready by observing approximately 20K to 50K (or more) bacteria/archaea and 20 to 200 flagellates per 250X field of view. I can do the math to convert that to numbers/ml if you like. In addition to this there was fungal hyphae but I usually only looked for presence and did not attempt to record volume. This was applied through overhead irrigation. We also topdressed the ‘spent’ VC so benefited from this as well. Besides this, the only other application was a minor topdress of fish hydrolysate once a season (some seasons not at all). We had successful crops ongoing of flowers, herbs for market and vegetables for on farm consumption.
    It was highly successful using nothing else for 7 years. I have a farmer buddy with a similar but longer experience.

    If we had more of our own animals we likely would have used compost but as it was we only had a limited supply. There are those who are in the same boat. They cannot afford to have compost shipped to them but they can have a worm bin and make compost tea. Someone mentioned using carbon fuels to pump air. What about the fuel used to make compost and transport it?

    Before I am pigeon holed as one of the big money makers (I wish), note that I give instructions on my webpage for making your own compost tea maker, even with a stick and bucket.

    Linda, it sounds to me like you have not spent enough time looking down a microscope tube, otherwise you would know how simple it is to grow out bacteria/archaea, flagellates and various other protozoa and fungal hyphae from compost or vermicompost in a liquid (water) just with a bit of molasses even in a pill bottle, nevermind an aerated compost tea brewer.

    You may come to my humble lab if you wish and I’ll be happy to teach you.

    I think the whole thing that worrying about a few anaerobes is overblown as someone mentioned.

    As far as nutrient cycling, you are looking for large populations of bacteria and protozoa. ‘Very simply stated’ when the protozoa consume the bacteria nutrients are made available to the roots of plants.

    Please have a look at my video footage for illustration;

  9. Hi Tim, Let me be blunt — all you just did was provide a testimonial that compost tea worked. This is not valuable to researchers because it wasn’t done in a controlled manner. Counting microorganisms is all well and good, but it doesn’t prove anything. Just having microorganisms there doesn’t mean they do any good. How do you know none of the bacteria were e-coli? Did you test? We do have published data showing that these microorganisms can live in ACT.

  10. These crazy blogs will drive me nuts. Sorry but for some reason it posted my other post again.

    Jeff, you are entirely correct and a controlled study is nice, [although the ones you mentioned regarding the ecoli are flawed, as I have written about previously] but what I have stated is what I have and often farmers look at some peer reviewed people only as laking some important elements, such as hands in the dirt. I did not only give a testimonial but also referenced some pretty darn good researchers…..right?

  11. Tim, your testimonial is about compost tea. I think the people on your list of references are all soil science researchers, correct? I haven’t looked through all of their publications, but checking Bonkowski and Clarholm I see no publications on compost tea.
    If I’m missing something, please correct my thinking. Otherwise, you’re mixing apples and oranges.
    And for the convenience of readers on this blog, can you tell us why the published research on E. coli contamination of ACT was flawed?

  12. Very briefly, apparently you have a slight comprehension disorder as I never stated my references pertained to compost tea. Please reread.
    Regarding the studies which showed e-coli grew in ACT, I really should have specifics as to which studies you reference but the ones I read originated with the USDA and the Can Dept of Ag. and both
    1/ had to inoculate with a ‘friendly’ e-coli and 2/ both did not track protozoa predation among half a dozen other obvious weaknesses.

    Could we not do a similar study to ‘easily’ show the growth of the same strain of e-coli in compost?

  13. OK, Tim, snide comment aside, you said this: “I did not only give a testimonial but also referenced some pretty darn good researchers…..right?”

    So why did you mention a testimonial about compost tea in the same breath as your list of unrelated soil science researchers?

  14. As a field researcher I have my hands in the dirt almost constantly. I run an 8 acre nursery on campus where I have tried compost tea with no effects. Saying that Linda has a comprehension disorder might have been amusing to you, but come on — you said you referenced some darn good researchers — the only ones you mentioned were the ones Linda mentioned (then again, it’s possible I have a reading disorder), so she assumed those researchers studied compost tea — so did I. Bummer, I must have a comprehension disorder. And…the article I’m talking about showing that compost tea certainly can harbor E. coli strain O157:H7 is right here — and it certainly did test the right strain. See here ( The supplements mentioned would be something like molasses. Protozoa predation is immaterial — the test was for the bacteria.

  15. I addressed the use of compost in my original post (and soil in general). My comment to Jeff was not related. It was meerly a statement that I did not just make a testamonial. Read much? The invitation is open, if you wish to learn. Over for tonight.

  16. Okay Jeff, you slogged me back in momentarily. Where on this page has Linda referenced those researchers? You assume I’ve read something not presented. I was not supporting CT with the references but what has been researched regarding microbial based ag/hort concerning compost. I stated I did not know which e-coli studies were referenced. And Protozo
    a are not relevant??? Oy vey. Who needs to be looking down the tube?
    I don’t think I can keep it up with this blog format, as I cannot seem to view Jeff’s statements while I write. Anyway Jeff, the invitation is extended to you as well to come to my little farm and lab. byebye

  17. Tim, The fact that you cited some researchers who never did anything with compost tea isn’t a particularly useful point if you’re trying to prove you didn’t “make a testimonial” as my stating that you provided a testimonial simply means that you noted your observations rather than providing good research. And I made the same “mistake” Linda did. Between Linda and I we’ve written eight books, so I guess we can probably read OK. If you wish to learn from someone who actually does research and publishes what he finds, the invitation is open. I’m sure Linda feels the same way.

  18. I don’t quite understand why foliar application of compost tea is being considered the same as the use of compost in soil. The applications are very different. The scientific method, in which I’ve spent my life, answers very limited questions, one at a time. It can measure measure simple things, but does not seem very useful for dynamic products like compost & compost tea. It doesn’t surprise me there’s not a lot of controlled studies, but observational studies can be just fine in complicated biologic systems. If waiting for “science” why not just go back to “N-P-K” (really simple!) and forget about the rest? I trust that won’t happpen because of an inappropriate insistence on randomized scientific trials. When I see human patients they are an “N of 1” study every time.

  19. “inappropriate insistence on randomized scientific trials”…Wow…I’m speechless. So we don’t need to prove something works? Observational studies are fine? So, those observational tests that showed that drinking DDT won’t hurt anybody that various professors conducted in the 1950s and ’60s (by drinking DDT) — should we believe those? Where do we draw the line? Perhaps you could point me to a paper in some reputable journal which would tell me when observational studies are OK and when they’re not.

  20. Eileen, just to keep this thread focused, we’re not discussing foliar application of compost tea, but soil application. I’m sure you agree that applying compost to soil is appropriate. And to be clear, there have been a lot of controlled, published studies on compost tea – it’s just that the results don’t support its use, either as a foliar disease suppressant or a soil nutrient booster.

  21. The problem with you research types is you don’t understand the power of ritual. Compost tea is a holy sacrament used by the nurturers of plants and the acts of brewing and applying it helps one focus with devotion to the flora flock in a meditation of love. It’s about faith.

    Good work Jeff and Linda- I just love research when it confirms my beliefs! I think in this case the research is strong enough to convince most people without preconceived notions that manure tea has not been validated by science.

    I think if I ran a farm, I’d use a small patch for a controlled evaluation of any given practice before endorsing it when it involves contraversy or just more work. I do some of that in my nursery, and though I don’t expect it to be used as an info source by others it at least gives me a stronger position to make my assertions.

  22. The fourth sentence I wrote should have read, “I think, in this case, the research is strong enough to convince most people without preconceived notions (otherwise), that manure tea has not been validated by science.”

    Not that anyone cares, but without commas the sentence appeared to suggest the opposite of what I intended to say. Tad, I hope my attempt at humor didn’t contribute to your frustration. It was only a joke and not intended to imply that all who endorse manure tea reject science. However, all of us tend to elevate the legitimacy of our own anecdotal observations- I buy into the evolutionary cognitive psychology viewpoint that we are genetically programmed to do so- even scientists are often guilty of this, IMO, and it can show up when they are analyzing and interpreting research. However, their training has to help them moderate this tendency.

  23. Alan: Compost and not manure. It is working with the same set of organisms and pretty much the same hypothesis/theory of nutrient cycling. Speaking for myself, it was the research [my own] which led me to compost tea [laboratory extraction and multiplication of soil/compost microorganisms; I hate the term compost tea!] and not the other way around. I believe in compost tea no more than I do compost. I also incorporate Glomus Intraradices inoculation/infection but do not worship mycorrhizal fungi either nor give it attributes it does not have as some seem to do. From my perspective, I do not rely on faith that I have a certain set of organisms in a compost tea prior to application because I verify that via microscopy. I do however admit to a certain amount of faith that once applied, those microbes survive and continue to cycle nutrients or otherwise function in beneficial habituation. This is the same faith I draw from when using a topdress or mix of [vermi]compost, a faith mixed with research, learning and experience, really very similar to the faith exercised which expects an apple taste when biting into one of those red or green things which grows on the trees in my yard. To me the best approach is a balanced one and compost tea has been a useful tool (or so it appears) in my growing experience which is still growing.

  24. Hey, I really wish to continue this dialogue, unfortunately I haven’t had much time due to work constraints (opening a new business is a ton of time!). We are in the process of opening a retail location on 7 acres in Redmond that will incorporate an organic produce stand and coffee shop, an urban farm/feed store (chickens, ducks, feed, etc…), an organic hydro/soil shop, an 80 ft commercial production organic tomato greenhouse with aquaponics, a vermicompost facility, education center, and much more.

    As I stated in the email that got erased (grrrr….), I’d be happy to set aside a test plot where we could agree upon the methodology and controls and I would volunteer to do the microscopy on the teas.

    I’d also love to have a discussion in general on the topic in person, as it’s hard to type all your thoughts and also it’s easy to misinterpret peoples words/intentions.

    Getting back on topic though, I do agree that there needs to be more studies surrounding compost teas and their efficacy. Just because some of the current data doesn’t support it, doesn’t mean that it is “snake oil” or that the people involved are greedy. I truly believe in what I do and have seen the evidence of it’s efficacy first hand. I get calls all the time from people that are quite happy with the results they’ve gotten since using ACT on their gardens and container plants.

    Jeff, I am in full agreement with you on the benefits of compost and mulch, and highly encourage all my clients to use them first when po
    ssible. I also am a proponent of worm castings, especially ones made on-site from a worm bin. The microbial activity in worm castings is amazing and much more consistent than other forms of composting.

    I also agree that in a healthy organic system that ACT will have little to no effect. If you create a good organic system with proper nutrient cycling, then ACT may not be the best option. However, I do think that in less than ideal conditions, ACT can have significant benefit.

    There are some of us out there that really believe in this technology and do our best to promote it responsibly through the science available to us and I can tell you how frustrating it is for me that there are people throwing an aquarium pump in a bucket with an air stone and marketing it as ACT without any proper testing.

  25. Coincidentally, I was one of the reviewers of that manuscript. I found it to be of marginal quality and had several concerns I felt needed to be addressed before it was published. For whatever reason, they weren’t. Here’s a summary of the major problems I saw:

    1) The abstract overstates the effectiveness of compost tea as a nutritional source. The data demonstrate that Osmocote is by far the most effective source of nutrients in terms of measurable plant response. Compost tea is a poor source of nutrients. The abstract also does not reflect the discussion, which is more hesitant and speculative.
    2)In many cases, the authors use nonreviewed and/or unscientific sources to bolster claims, often putting them on par with peer-reviewed articles. For example, the two articles in BioCycle (a nonscientific publication), and the book published by Soil Food Web, Inc. (a nonreviewed publication) are used repeatedly throughout the paper, often as the sole supporting source of some particular point.
    3)There were multiple comparisons made among treatments throughout this study. The probability of a significant effect occurring strictly by chance increases with the number of comparisons. Therefore, it’s necessary to run a Bonferroni correction, a more conservative analysis that helps eliminate the occurrence of false positives. This correction needs to be made for all analyses in this paper.
    4)The results of the study are so variable that the discussion is weak and speculative. The words “can,” “might,” “possible,” “likely,” “suggest,” “may,” “could,” and “imply” were used at least twenty times in discussing the results. This is in direct contrast with the abstract.
    There is an interesting nugget of information buried in the discussion which is not reflected in the abstract, either – which is that “aeration is not essential for plant growth promotion.” So even if we were to accept this article at face value, it appears that aeration is just a waste of energy.

  26. Linda,

    Did you ever review the Harvard Study that incorporated ACT? I’m sorry that you feel that the study isn’t up to your standards. That’s sort of how I feel about the studies you source in your “myths” article on compost teas! Let me know if you want to take me up on my offer, and I will try to provide you with other studies when I get the chance. My entire point is that rather than bash an industry/technology in such black and white terms, what about being open to the possibility that there may be benefits beyond what you think “current research” supports? My 2 cents….

  27. Linda,

    Why are you ignoring my other questions and focusing only on the journal/study issue? Are you unwilling to step outside of your academic circle for a moment and address the rest of my posts?

    I don’t have the same access to scientific journals that you do, being as how I’m not associated with a University. I’m assuming your last post was your way of claiming that the work done at Harvard is “insignificant” because it wasn’t published in a scientific journal or possibly hasn’t been peer-reviewed (I have no idea if it has been or not). I made an offer to you to setup a study on our property, which you haven’t responded to. I’ve also brought up other aspects relating to our industry that you’ve ignored as well. I’ve already stated that there is not enough research out there on ACT. I still feel that the body of research that you cite from is full of errors as well. I would love to get my hands on the study that you posted above if you would be willing to share it.

  28. Tad, let’s be rational here and assume I do have duties outside monitoring the blog 24/7 and that I’m not “ignoring” you.
    Look. As Jeff said, all of us as scientists HAVE to be open to other possibilities, or we wouldn’t be very good scientists. But the way it works is that we have to see published evidence before we can begin to shift our thinking about a topic. So yes, whatever was done at Harvard doesn’t count until it’s published in a scientific journal. Jeff and I have tried to explain this ad nauseum. You need to accept that these are the parameters we work within as reputable scientists. So when you ask me to step outside my academic circle, if that means stop doing my job as a scientist, I guess the answer is no.
    Now, as for doing research on your property. The way this works – if you or any other business wants an experiment designed and conducted by a scientist at a university, you provide grant money to do it. Again, these are the parameters we work within.
    Finally, I don’t know what study you’re referring to in the last sentence. Do you mean the one with 4 numbered points from March 4? If so, it’s the one you gave a link to.

  29. Linda,

    You’re missing my point. My reference was to the fact that there has been a lot more substance to my posts besides just the studies which you’ve so quickly dismissed.

    The study I would like to see is the Here’s a recent one published in Arboriculture and Urban Forestry November 2011 (Laboratory Assays on the Effects of Aerated Compost Tea and Fertilization on Biochemical Properties and Denitrification in A Silt Loam and Bt Clay Loam Soils, 37(6): 269–277).

  30. Linda,

    Here’s another study on liquid compost/vermicompost extracts:

    I think it’s unfortunate that you’ve built your reputation on bashing ACT. It doesn’t surprise that you would turn down my offer to run a test plot on my property. I understand how the University works and the grant process. That’s one of the reasons I think we haven’t seen good studies on ACT. Fertilizer companies have a lot more money to devote to these sorts of studies. What would happen if you found that ACT had a significant impact on plant health/growth?

    For how little research there is on ACT in general, how do you justify the amount of “bashing” that you do in regards to the technology? Is that the behavior of a “reputable scientist?”

  31. The second study you note is interesting, but it’s far from conclusive and isn’t really testing things in “the real world” so I question its applicability.

  32. You will need to go to the UW library to get this article. I would be violating copyright to send it to you. AUF does not grant open access for one year after publication. As for the link to the report, I will look forward to reading it in the appropriate scientific journal where it can be weighed equally with all of the other studies that you have dismissed.
    Tad, you don’t like my message, but that doesn’t mean it’s “bashing.” Nor have I based my reputation on bashing compost tea. Unfortunately you have a very narrow understanding of what I do. You are more than welcome to look at my online cv or I can send you an electronic version if you would like to learn more.

  33. Tad, If you’re serious about wanting to do a study on compost tea drop me an e-mail. I’d like to walk you through how to go about setting up a study, and I think it would be useful and informative for all of us if you conducted one.

  34. Jeff,
    I would be interested, I am currently in the design process with Jessi Bloom on our property and I can have her set aside an area if you are interested in coordinating something with me. I would want to know in advance that the results would be accepted by yourself and Linda as legitimate (even though they probably would never be published in a scientific journal). How do I email you? In response to your post, I’m not claiming anything conclusively. My point was merely that there needs to be more research and that there are those of us in the industry that are actively interested in pursuing scientific research in this regards and we’re not all out there making irresponsible claims regarding compost teas. I’ve always felt that Dr. Ingham has taken too many liberties in her own right regarding ACT, in much the same way that I feel that Dr. Chalker-Scott has gone out of her way to dismiss it. I think the answer regarding it’s efficacy lies somewhere in the middle. It’s a tool, not a silver bullet. I sincerely believe that ACT can have a positive effect on plant health and plant growth. However, I do think that it’s ability to suppress and control disease has been exaggerated. On this we would agree. I say “bashing” because rather than calling for more research, I see Linda essentially saying that “compost tea is bad” and that people in that industry are out to take advantage of people through emotional marketing. And while this may be true of some people in any industry, I don’t think that it’s a fair characterization of the technology or the majority of people in the industry. I work really hard to promote all aspects of organic gardening and what I like to call “biological horticulture.” Essentially, gardening with microbes in mind (compost, mulches, and yes, ACT in some cases, along with good soil amendments like kelp, fish hydrolysate, and humic acids). To feel like I’m somehow considered a snake oil salesman or charlatan in your eyes because I promote or use ACT does not sit well with me. Does that make sense?

  35. Tad, I can be reached at Please don’t put any words into Linda or my mouth. Just because we don’t believe that compost tea is particularly useful doesn’t mean we think you’re a charlatan — that would mean that we believed that you didn’t believe in your product and were selling it to make a quick buck — based on your comments here I doubt that. We don’t bash, we point out what current research shows. I’ve read most of what Linda has written about compost tea and I agree with it and think that it has been fair and within the boundaries of what the research currently says. Please realize that no experiment you can conduct would PROVE to us that compost tea works. However, if the experiment is well done, it will certainly influence our thinking. I’m not guaranteeing that I’ll accept the results, but I will certainly consider them. No experiment, published or unpublished, can do more than that.

  36. Thanks guys for removing those clearly rediculous spam posts from yesterday.

    On the Compost tea question, my only usage for such an item would be for house plants which need constant regular attention anyway. The tea preparation has always looked time consuming anyway. Beyond that I totally agree with Jeff & Linda on it being not only a waste of time(especially for something large scale) , but also that there won’t be any noticable difference than if you simply used good compost and mulches.
    The ONLY possible benefit may be if you have some type of commercial operation and dealt with lawns and sports fields. In fact, in one of those links I noticed there was some additives such as humic acids and other ingredients being added to the compost tea mix anyway. The ONLY benefit I could see is if you were to do it in say, springtime and only after doing a bit of aerating of the turf. Most chemical fertilers are water soluable anyway with those lawn sprayers, so if you wanted to add your tea, than so be it. Still, there is alot of work that appears to go into the correct formulation and I noticed in one pic that there was a heavy piece of expensive looking equipment.
    I still believe for all shrub and tree plantings , mulch is your best landscape feeding program. The landscapes I supervised and maintained were always heavily mulched down in So-Cal. Not only did it slow release the nutríents thru the process of microbiological breakdown and small critter moving and tilling, but most importantly it saved on water. My mulch broke down rapidly. In fact we had to do it every few months. Many tree trimming companies had to pay a fee to dump their loads. But give’m a call and if they were in the area, they were happy to leave it off. Of course it was also important to know what type of trimmings they had.
    For me I don’t use composting teas for the same reasons I don’t believe in any type of soil ammending. Not that it is bad. There’s simply no noticable difference and that simply translates into a waste of my money for the ammendment. I also want the newly planted seedlings to get immediately used to what ever native soil they were going to become permanently apart there rest of their lives as quickly as possible.
    Again, at best I would say for house plants only or as I’ve used in the past as a temporary feeding program for newly emerged seedings in the flat trays to be transplanted into pots of the ground.

    Here a question for Linda. I never liked using chemicals for nursery soil debugging. You know, the type of debugging so that you don’t get damping off in the nursery flats? Have you ever mixed Hydrogen Peroxide with water as a potting media drench? I’ve purchaed and used the food grade powder as an additive to the water I’d drench in each tray prior to planting and never had problems with damping of. If I didn’t, I’d loose 70% seedling death rates.

    Thanks for your articles!

  37. From Linda (I believe) “who fight the compost t
    ea battle:”
    “you don’t like my message, but that doesn’t mean it’s “bashing.”

    From Jeff
    “We don’t bash, we point out what current research shows.”

    Didn’t need to look far to find works that speak for themselves.
    Onward compost tea soldiers, marching on to battle!

  38. @Kevin, I’ve made a note to do a literature search on hydrogen peroxide use as a drench. I’ll post something when I get the chance!

  39. Thanks Linda. I have googled in the past and again just a couple of days ago when bringing this question up for you to address in a future post. There is quite alot of interest out there on the subject, but not necessarily where you see it’s use on any large scale agricultural or commercial horticultural ventures. Mostly seems to be small times operations or avid home gardeners and plant enthusists. Nothing wrong with that, but I wish more large scale interests would at least try it in view of the potential environmental importance. Thanks again for future posts.

  40. I have tried hydrogen peroxide as a foliar treatment in a replicated study to control black spot — it was useless.

  41. Personally Jeff, I’ve never used Hydrogen Peroxide for anything other than Nursery Potting media sterilization. I’ve never used it as a fertilizer beyond that as an addition to any feeding program. After I have innoculated seedlings in pots with VAM and once established, I’ve never considered the further use of H2O2 to be of any further benefit. Of course that doesn’t mean it may not be of benefit. I just never experimented beyond soil preparation for seed germination.

    As far as use on roses, I have read something on this, but wondered more about powdery mildew and rust more than anything else. Every geographical location has it’s own set of climatic circumstances and unique problems. With roses I’ve found that staying away from specific varieties prevented my toiling over problems associated with those varieties more susceptible than others. Fame is one of the easiest to grow for rookies. In So-Cal it kept it’s colour on the plant for well over a month. The petals turn almost paper-like the same way as they do with Sea Lavendar, etc. Of course, there is almost ZERO fragrance, so maybe there are some tradeoffs.

  42. Here’s a new perspective on Compost/Fertilizer Tea! Hmmmmmmmmmmm??????
    Chinese Tea grown using Panda dung as Fertiliser

  43. The widespread adoption of ACT used as a foliar application probably worries big business, and the scientists who depend on their grant money, the most. After all, who stands to make a buck from a farmer stirring, with a stick, a bucket full of water, local compost, and some micro-critter food?

    Keep pushing miracle grow – Sustainable farmers will stick to fermenting.

    Rock on.

  44. @urbanFarmer

    Good grief. What a ridiculous viewpoint.

    Hey, who “stands to make a buck” when I make compost? Anybody, except me?

    And of course LCS already brought your point up, so what original discussion are you bringing here?

  45. Kevin, I missed your earlier post until just now. All I can say is….ick.
    Ivan, your link doesn’t work. Please check the address and repost.

  46. Compost tea is probably a useful thing. But the matter is that it takes a lot of time to be prepared and nobody knows what kind of bacteria and funguses he grows. Together with useful bacteria there can live harmful fungi and other plant diseases in your compost. Instead of it you can take already done and guaranteed microorganisms which will work in the soil and on plants as fungicides and insecticides. Any harm, any lost time, any equipment. The whole you need is the biological preparation and water. To be sure visit the page Believe me you’ve never seen something better.

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