Permaculture and the Ethylene Cycle Myth

I first came across references to The Ethylene Cycle in ‘The Earth Care Manual’ by Patrick Whitefield. It was my first ever Permaculture book, and one that I still refer to. The last Permaculture book that I bought was ‘The Permaculture Handbook’, by Peter Bane. It too describes the Ethylene Cycle. Strangely enough I do not recall reading about it anywhere else. In my last post (Balancing Soil Minerals Pt 2) I was reminded of the Ethylene Cycle by a comment from Darius, a fellow Permaculture Practitioner, and decided to look at it more closely.

What is the Ethylene Cycle?

The diagram below gives a quick overview of what the Ethylene Cycle in soil is claimed to be, and what it is supposed to do. It is taken from a Permaculture Site, and we’ll be looking at the accompanying text shortly.

The Ethylene Cycle in Soil

The Ethylene Cycle in Soil

A highly simplified explanation is that Ethylene helps to suppress microbial conversion of organic matter, and helps make available some nutrients to plants.

The Ethylene Cycle and Me

When I first read about the Ethylene Cycle I recognised it, as it was described, as a justification for not digging or ploughing. As I was already convinced that ‘No Dig’ gardening was the right approach, I didn’t bother to investigate it further. When my approach to digging changed, I overlooked the Ethylene Cycle until Darius reminded me of it. A quick bit of internet research, and some help with accessing the original research paper (Thanks Jan), allowed me to dig a bit deeper into this frequently taught piece of Permaculture folk lore.

Permaculture and The Ethylene Cycle

I couldn’t help thinking that there must be an underlying reason for the tight focus on this one piece of soil science by Permaculture Practitioners, and I found it with my first internet search. If you type ‘ethylene cycle in soil’ into your browser and search, you will find the Permaculture College of Australia article fairly close to the top of your list. If you read it it gives you a more detailed explanation of the Ethylene Cycle, and adds a layer of how it justifies or proves the need for no dig/ no plough techniques. The article also hints at why it may be far less appropriate for the UK climate and conditions, but I will save that for later. In the meantime, why not read the article. You can access it directly from the link below.

Permaculture College Australia

 

The article is a highly edited version of a 1976 Australian paper, and the article states that it was published in issue 7 of the International permaculture Journal in 1981. It was then published again in issue 39 in 1992. My initial thought were that this was a 37 year old paper, published twice in Permaculture Literature, and then spread by other Permaculturalists, with little critical thinking or analysis. The concept seems to have been completely ignored by other scientists, which implies to me that it was either proven to be inaccurate, or that it was perhaps irrelevant in some way. Again it was strange how little was written about this process that didn’t originate from this single paper.

Critique of the Permaculture Article

Relevance for Cool Temperate Climates

In the Introductory passage to this Ethylene Cycle article, the editor writes about soil aeration, and the perceived problems that it brings, principally the loss of soil organic matter through decomposition by microbes. She then writes ‘ The ‘Aeration Theory’ really developed in the northern hemisphere where the extended cold winters prevent microbial decomposition of organic residues in soil. In spring it is advantageous to stimulate the decomposition rate so that plants can obtain nutrients during a relatively short growing season’. This is then contrasted with Australian conditions, concluding that they are very different. So the editor is actually outlining why aeration is advantageous in temperate climates, and I wholeheartedly agree. Sadly, this part of the article seems to have been completely overlooked by the Permaculture network, operating in those cool winter climates. Instead it takes the opposite view, using the Ethylene Cycle as its justification

The rest of the article is written by the author of the research paper, and in it he claims that:

  1. Ethylene is a critical regulator of the activity of soil micro-organisms and, as such, affects the rate of turnover of organic matter, the recycling of plant nutrients and the incidence of soil-borne plant diseases‘.
  2. Ethylene does not act by killing soil micro-organisms, but simply by temporarily inactivating them
  3. He also discusses the role of anaerobic conditions and ethylene in the release of unavailable soil minerals

There was not enough of the underlying research and data in the article to justify the claims made in it. So I decided to read the original Research Paper.

ETHYLENE IN SOIL BIOLOGY. A. M. Smith

The research that the permaculture article was based on was titled Ethylene in Soil Biology, by A. M Smith. The paper was published in 1976. Sadly I cannot publish the paper for you to read, so I’ve had to quote directly (in italics) the bits that I feel are relevant. If you have access to academic paper through a University, please look at the original paper, and compare my analysis with the original work

With only a cursory initial reading on this Ethylene Cycle paper, a couple of things really leapt out at me.

The Effects of Ethylene on Plant Growth

The first concern came in the Introduction where the author states that only Cursory attention is paid to the significance of ethylene on plant growth and seed germination. That seemed strange when the whole point seemed to be to show it’s importance to plant growth. The paper then quotes other research papers which ‘showed that it may adversely affect plant growth‘. I was taken back a bit by this as it didn’t seem like a good reason to want to encouarge ethylene production. There was no research undertaken into which plants would be harmed by ethylene, but the paper mentioned that lowland rice was unaffected by quite high concentrations, whereas tomato, tobacco, and barley were ‘sensitive to trace amounts‘. It puzzled me why this would be seen as a good thing.

The author of the paper mentions reports that ethylene inhibits the nodulation of leguminous plants. This is really important, as many of the potential solutions to providing a sustainable agriculture involve nitrogen fixing plants. If ethylene inhibits the fixation of Nitrogen by them, this would be an argument to prevent its formation, not to encourage it. In fairness the author does quote from another, older, paper that Nitrification is enhanced near legumes and that this would restrict ethylene production ‘and may permit unimpaired nodulation under most field conditions‘. My emphasis.

The Effects of Ethylene on Soil Microbes

The permaculture article included references to Ethylene stating that ‘it is a critical regulator of the activity of soil micro-organisms and, as such, affects the rate of turnover of organic matter, the recycling of plant nutrients and the incidence of soil-borne plant diseases. ………… Ethylene does not act by killing soil micro-organisms, but simply by temporarily inactivating them‘. This is directly contradicted within the research paper in a number of areas. The first reported on the premature lysing of fungal hyphae by ethylene. This link on LYSIS explains that it is the breaking down of a cell compromising its integrity. Whilst not strictly killing fungi, it certainly doesn’t appear to be good for it either. With fungi having such a key role in the decomposition of organic matter, and in their mycorrhizal associations with plants, I fail to see how this is a good thing, or something to be encouraged. The paper also reaches the conclusion ‘that bacteria are not directly inhibited by ethylene at concentrations likely to occur in soil‘. Later it states that ‘soil respiration may remain relatively high in the presence of Ethylene because soil bacteria do not appear to be directly inhibited by ethylene‘. Taken together it seems difficult to justify the claims that Ethylene controls soil microbes harmlessly. The two principle components are either damaged (fungi), or unaffected (bacteria). In fact my more detailed reading suggested to me that many of the claims that were made on behalf of Ethylene could be attributed to purely to anaerobic conditions, however they were created.

The Effects of Temperature

The permaculture article touched on the differences between cold winter areas, and those with warmer conditions. This is directly referred to in the research paper, which links a twentyfold reduction in ethylene production from 11 C down to 4 C. A reflection of the reduced microbial activity as temperature falls. Stating that by restricting microbial activity, cold winter temperatures reduce the need for additional regulators such as ethylene. To put that in simple terms, in areas with cold winters, little organic matter is decomposed by microbes, making aerating the soil by ploughing or digging significantly less of a problem that in warmer climates, and allowing for the retention and build up of more organic matter in the soil than under warmer (Australian) conditions.

The Effect of Organic Material on Soil Microbes

The paper notes that the addition of organic matter overrides any suppressing effect that ethylene might have on soil microbes. This is attributed to an excess of nutrients, and is portrayed as a good thing, allowing the rapid processing of surplus nutrients. However this describes the situation in many no dig/mulched gardens. The layer of organic material would seem to override any potential benefits that might have been gained by the production of ethylene in reducing microbial activity. In plain language, even if ethylene did inhibit microbial activity, and that wasn’t the conclusion that I came to in the preceeding paragraph, it wouldn’t work in gardens/soils with high levels of organic matter.

The Mobilisation of Essential Plant Nutrients

One of the cornerstones of the perceived benefits of the ethylene cycle to plants is the claim that it has a role in making some minerals available to plants. To examine this claim takes an understanding of how ethylene is produced and some complicated soil science. Rather than try to explain how that works in a relatively simple way, there are a few things that I can highlight from within the paper and article that make the same point. Firstly, there is no direct evidence linking ethylene to the availability of these nutrients. The author of the paper is making an assumption that as these minerals are released in waterlogged soils, and that when ethylene is produced similar chemical conditions occur, the ‘availability of cations and anions should alter as markedly in these microsites as in flooded soils‘. Note the word ‘should’ which I have highlighted. No evidence is produced to support this, and the sequence that is described after this is a prediction based on what happens in submerged soils. To quote directly from the paper ‘Extrapolating from the chemistry of submerged soil, it is possible to predict the sequential seris of reactions in the anaerobic microsite that will lead ultimately to an increase in avaialability of inorganic nutrients‘. I don’t find this convincing. In fact there are some clear indications that the release of nutrients is not linked to ethylene, but rather to the conditions that produce the ethylene in the first case. This suggests to me that the ethylene is a passenger or bystander in another process, rather than the driver. The first is the diagram at the beginning of this post. To save you from having to scroll up to the top of the page, I’ll put it below.

Ethylene Cycle in Soil

Ethylene Cycle in Soil

If you look at the bottom left segment you’ll see that both the release of ethylene, and that of soil nutrients, are the result of a change in thechemical  form of iron, which in turn is the result of anaerobic conditions. The second is contained in the permaculture article, where the following is written about the release of nutrients. ‘The soil conditions necessary for this mechanism to operate are identical with those required for ethylene production‘.

In actual fact it is anaerobic conditions which create the chemical conditions that release these nutrients, not the ethylene. Those conditions include waterlogging of the soil spaces, compacted soil, and the CO2 given off by the rapid decomposition of organic material by aerobic microbes.

Summary

Many of the positive benefits atributed to the ethylene cycle don’t seem to hold up when looked at critically. Inhibition of soil microbes by ethylene seems to be restricted to the damaging of fungal hyphae, with no direct effect on bacteria. Not that I think that it’s a good idea to inhibit them in the first place, but it’s promoted as a benefit to retain organic matter in the soil. Even were ethylene able to do so, not only is it far less important in temperate climtes, but that effect would be inhibited by the addition of large amounts of organic matter, like those used in mulched gardens.

The negative effects of ethylene on plant growth, the germination of some seeds, and nodulation of leguminous plant roots, would seem to be sufficient reason to discourage its production, and not to encourage it.

The release of insoluble nutrients by ethylene is an unproven prediction, with the anaerobic conditions created by water or microbial respiration likely to be the real agents for this process.

The thirty year love affair of permaculture with the ethylene cycle seems to be based on very shaky foundations.

Comments and Feedback

I’d welcome comments and feedback on this post, but especially from those with access to the research paper, who can compare the post with what is contained in the original.

 

 

 

 

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30 thoughts on “Permaculture and the Ethylene Cycle Myth

  1. MikeH

    You say The thirty year love affair of permaculture with the ethylene cycle seems to be based on very shaky foundations.

    I’ve found the same thing with dynamic accumulators. A Google search of the phrase yields a lot of permaculture references and this list – http://oregonbd.org/Class/accum.htm. It looks like they all lead to Robert Kourik’s Designing And Maintaining Your Edible Landscape Naturally – http://www.robertkourik.com/books/edible.html, first published in 1986. Kourik’s table does have references but none of the ones that I could find have bibliographies or references and has no indication of the source of the charts used. There is a database that does provide nutrient details of many plants: Phytochemical and Ethnobotanical Databases at http://www.ars-grin.gov/duke/. Starting with Wiki’s list of plant nutrients, I searched Duke’s database for those plants with the highest concentrations of each of the nutrients and constructed a spreadsheet – https://docs.google.com/spreadsheet/ccc?key=0Aoz8GE1bbsDjdDdxSjA3dWxKaU5qU2xVZUFUcHR4RGc&usp=sharing. It’s a surprising short list of plants – Lambsquarter, Pigweed, Stinging Nettle, Dandelion, and Red Clover. Interestingly comfrey does not make the list as a dynamic accumulator. Note that the list is assembled based on perennials that are hardy to US Zone 4b.

    I suspect that comfrey occupies a similarly elevated place. In that case, all paths seem to lead to Lawrence Hill

    Reply
    1. Deano Martin Post author

      Hi Mike
      Thanks for that list and the links. I’ll take a look. More good stuff to read.
      All of the best
      Deano

      Reply
    2. Alan

      That’s very interesting Mike, for two reasons. Firstly I hadn’t realised that the idea of dynamic accumulators rested on such a narrow base. Secondly, I had always understood that the rationale for using them was that they were plants capable of rooting deep into the soil, scavenging nutrients from the lower soil horizons and bringing them to the surface. Out of the list of plants you mention from Robert Kourik, red clover and stinging nettle both have notably shallow, mat-forming root systems, the goose-foots are not particularly deep-rooting and dandelion might have a strong taproot but hardly the deepest in the garden. If the rationale is purely that they accumulate high levels of particular minerals in their tissues then what is the point of that?

      Reply
      1. Deano Martin Post author

        For Alan and Mike
        Sorry that questions between the two of you can’t be moderated autmatically, but doing so makes a lot of work deleting spam.
        I try and check the blog each day, and I’ll get to it as quickly as I can
        Deano

        Reply
      2. Nicollas

        @Alan:

        I think that deep rooted roots are an evolutionnary advantage in poor soils, in that the taprooted plant can digg minerals not availble on the top layer of soil profile.

        Plants with shallow roots (nettles, mints) are effective to catch ‘available’ fertility and thus can develop in such environments.

        I’ve read some years ago a definition of a dynamic accumulator that i find relevant, but i don’t know if it is extensivly used, which is that a plant accumulate mineral X if the concentration of mineral X is greater in the plant tissus than in the soil surrounding it.

        (sorry for my bad english, i hope to be understable)

        Reply
    3. Nicollas

      @Mike

      I think there is maybe a flaw in your chart and that it is what is meant by “dynamic accumulator”. Is this the plant with the best nutrient level (as in your chart), or the one that can mine effectivly minerals in a mineral deficient soil or minerals that cannot be available to other plants ?

      For me there is not a good or bad definitions, the both are relevant wrt what you want.

      The first class to whose nettles belong, is great to catch fertility before it leaks elsewhere, and generally you export some parts of the plants to enhance fertility elsewhere. So such species are usefull around compost, housecoop etc (spreading issus set aside)

      The second class whose confrey belong, is great to catch already ‘lost’ fertility. It can be in deficient soils, or in fertile soil, to catch some of the abundant fertility that cannot have been catch by first class species. In the first case the cut parts are leaved in place, in the second it is export elsewhere. I’ve read that confrey + mind is a good polyculture, and it is an example to mixing the two types of dynamic accumulators in the ‘fertile soil’ scenario.

      The chart you’ve made is definitly interesting, but without informations about the fertility environment they were taken from, i dont know if it is relevant to compore the accumator power of two species ?

      Reply
      1. Nicollas

        By the way, after extensive searches both on the net and scientific publications, and after having read two books by Lawrence Hill, i’ve never be able to compare N or K content of bocking 4 and 14. There is one lab result for the both, but not taken at the same time of year, and he says himself that concentrations vary greatly with season…

        We need more permaculture geeks

        Reply
        1. Deano Martin Post author

          Hi Nicollas
          A nice bunch of comments. I particularly like the one calling for more permaculture geeks.
          All of the best
          Deano

          Reply
      2. MikeH

        Nicolas,

        You ask a very good question. The data in the chart simply is an analysis of the mineral content in the plant. Whether or not the plant is a good accumulator of the mineral is an open question although it would seem that would be the case. It seems to me that mineral content in a plant is a function of where the plant is growing. Since Dr. Duke assembled the information because he was looking for plants that might be useful in cancer research, I assume that he took that into account and that his data are not skewed. Hopefully, his numbers reflect samples taken from many climates and soils. Unfortunately, he is in mid 80s and doesn’t respond to emails.

        I would point out that all of the information floating around in permaculture circles with regard to dynamic accumulators has no basis in research data. It’s simply a table that has been repeated over and over. In communication with Robert Kourik, he has indicated that he published the data on the information that he had at the time and would not publish it today. In fact, after the book was published, he met Duke and discovered his data. Because his book never had a revised edition, he was never able to revise the data. As Kourik said to me, that table has taken on a life of its own. I guess that’s because it fits a view that permaculturalists want to believe. We definitely need some permaculture geeks to add balance.

        Regards,
        Mike

        Reply
        1. Deano Martin Post author

          Hi Mike
          Thanks for that explanation. It makes a lot of sense, and it would be useful if it were more widely known.
          Happy to join the Permaculture Geek Club
          All of the best
          Deano

          Reply
        2. Nicollas

          Yep,

          what we need for this DA thing is a motivated guy who has a lot of plant cadidates and to launch a fundraising to pay for a soil analysis and tissue analysis of each plant

          Reply
  2. Toby Hemenway

    I’m grateful to you for tracking this down. Several things always bothered me about the ethylene story as it was presented in those permaculture articles (my background is in biochemistry and genetics, which gives me an advantage here). But I never bothered to research it the way you did, so thanks for that. Now I am glad that, even though other permaculture teachers told me “you really should teach the ethylene cycle,” I never did, for just that reason.

    Reply
    1. Deano Martin Post author

      Hi Toby
      Thank you
      I hope that I’ve been as accurate as my current level of knowledge allows. Sadly I probably won’t be able to assess whether the post has any real impact on course/teaching content. The comments of people with your type of profile might get others to take it more seriously.
      Wishing you well
      Deano

      Reply
  3. Alan

    Thanks for an excellent article. It addresses two weaknesses that permaculture really needs to sort out. The first is poor reality checking in general and a failure to distinguish between well-supported facts on the one hand and interesting lines of research, anecdotes, hunches and guesses on the other. There’s nothing at all wrong with passing on the latter but they often get stripped of the caveats that they should come with and get passed on as gospel, especially if they sound suitably ‘sciencey’, as with the ethylene cycle.

    The second is the habit of taking ‘solutions’ out of context and reducing permaculture to a list of them. One example I can think of is Sepp Holzer’s use of large rocks to create warm microclimates by acting as heat sinks. It’s rarely mentioned that the context is that he is farming on a south facing slope. Out of this context they are as likely to act as cold stores depressing daytime temperatures when the plants are trying to photosynthesise.

    Cheers

    Alan

    Reply
    1. Deano Martin Post author

      Hi Alan
      I agree on both points.
      It’s a bit like a bioshelter. Great with plenty of winter sunshine, but perhaps not so good in a cloudy, misty, maritime climate.
      Wishing you well
      Deano

      Reply
  4. Tom

    I haven’t a clue about half of this. What concerns me though is that about 10% of my plot has been put over to comfrey. Are we saying comfrey as a fertility aid is bogus or isn’t it?

    Reply
    1. Deano Martin Post author

      Hi Tom
      I’ve not had a chance to look at the references, but I use comfrey too. Anything which creates such a large amount of organic matter is useful as a soil amendment. I think that Mike’s point is that not all of the plants normally suggested as being useful in gathering a surplus of nutrients in them, are as good as the claims made about them. I find that using comfrey as a liquid feed, or in my compost heaps, gives me a good response, but I have no idea (Now) whether there would be more suitable plants, that would give a better response.

      Reply
  5. Ute

    Thank you Deano for this critical analysis. I hadn’t thought about this for a long, long time. Some time in the mid 80s I met a permie in Germany who was translating Lea Harrison’s article about the ethylene cycle. I read it but wasn’t totally convinced either as I was studying soil science at the time at university and could not verify any of the assumptions made from my textbooks – no internet back then ….
    Had totally forgotten about it. However, on this chap’s advice I was converting a small vegetable garden at the time to mulch and no-dig – it was on very sandy soil in a continental climate with 600mm rainfall. In the autumn I covered the soil with some compost and chicken manure followed by 4-5 inches of oak leaves that had broken down for about a year plus some lime and rockdust; this thick blanket covered the garden over the winter until cultivation could resume in about mid-April by which time it had pretty much been broken down and converted into humus; it totally transformed the garden for the better in terms of fertility and the all-important water-holding capacity in that climate, an effect that quickly wore off after I left the place and the technique was discontinued. So the analysis may have been shaky, but the application proved worthwhile in this instance.
    I absolutely agree with Alan re “reality checking” in permaculture and anecdotes turning into gospel and being stripped of their caveats. In part this is due to tools in the toolbox being confused with the toolbox itself and tools being transplanted without critical analysis between continents, climate zones, different soils etc.
    As to comfrey, I would understand its nutrient accumulation role not only to be due to its deep root system but also as a function of its very high yield per unit area.

    Reply
    1. Deano Martin Post author

      Hi Ute
      In many ways trying to create that type of critical culture may be far more important than the accuracy of the original paper, or my critique of it.
      The ethylence cycle argument was only one part of a balance between the appropriateness or otherwise of digging. Again your toolbox and tool analogy is appropriate.
      Hope you’re well
      Deano

      Reply
    2. MikeH

      I absolutely agree with Alan re “reality checking” in permaculture and anecdotes turning into gospel and being stripped of their caveats. In part this is due to tools in the toolbox being confused with the toolbox itself and tools being transplanted without critical analysis between continents, climate zones, different soils etc.

      Ute,

      I think that part of the problem is that the itinerant teacher model of spreading permaculture has reached a lot of people for who permaculture resonates but who also have little or no first hand horticultural experience. As a result they have no way critiquing what they are being taught or knowing how to transplant to their situation what they are being taught. For example, when they hear about hügelkultur, they think that’s the horticultural holy grail. If they stop there, they miss John Jeavons, Emilia Hazelip, Mel Bartholomew, Alan Chapman, Ruth Stout, et al.

      It also seems to be difficult to question some of what is happening in permaculture today without being seen as attacking permaculture. It seems to me that there’s a great deal of defensiveness, perhaps in part for the theoretical/practical difference I outlined in the first paragraph.

      Regards,
      Mike

      Reply
      1. Deano Martin Post author

        I echo that.
        Permaculture Design starts with an aim or intent, and then assesses the best tools/methods to deliver that. Instead there is a homogenised version of permaculture, a sort of ‘permaculture by numbers’, which defaults straight to a no dig/mulch veg garden, with or without raised beds, and one or two dwarf fruit trees optimistically called a forest garden. Many of the arguments against digging don’t hold up when you start to look deeper into how soil/fertility/microbes/minerals/plants interact. Many of the perennial plants don’t produce enough to find a place in my garden.
        I think that’s a good an example of my goals driving the design process to produce a solution that fits what i want it to. The fact that I know of very few other permaculturalists who garden in any way other than the above suggests that there isn’t enough diversity, or that the ‘diggers’ are keeping a low profile.

        Reply
    1. Deano Martin Post author

      Hi Luca
      Thanks for putting up the link.
      This passage appears to be a summary of the original paper that I critiqued. There is nothing new in it. The same assumptions are made, linking ethylene with the release of nutrients, rather than the anaerobic conditions.
      Welcome to the blog by the way
      Deano

      Reply
  6. Patrick Whitefield

    I have to admit I haven’t got round to reading every word of your post, Deano. All I can say is I’m glad I took all reference to the ethylene cycle out of the second edition of the Earth Care Manual.

    Reply
    1. Deano Martin Post author

      Hi Patrick
      It’s possible that I missed something, but I don’t think so.
      Hope all is well
      Deano

      Reply
  7. Lusi

    Very interesting Deano, thank you.

    Does the Permaculture Association Research Working Group have anything to say on this, I wonder? It seems that this is precisely the sort of thing which we should be requesting students to research in more depth, particularly as they have access to equipment for experimenting (a great phd project?).

    The role play of the ethylene cycle which I have states that it is based on original research by Alan Smith (who’s initial funding was not extended). Lea Harrison followed up the available documentation, communicated directly with him and finally put it all together in a readable form in her article ‘soil fertility’. Not having time right now to research this further, but interested in hearing from others who do? Did you follow the lineage after Alan’s article to find anything else?

    Reply
    1. Deano Martin Post author

      Hi Lusi
      The post deals specifically with the research by Alan Smith, and the conclusions are my own. Although I found plenty of articles that mention this research, I didn’t find anything that developed it further.
      I think that the initial conclusions were wrong, but I discuss that in the post in some depth.
      The research group wouldn’t have the equipment to do this sort of work.
      It would be useful if others could take a hard look at some of the ‘research’ that we base our theories on. For example there are some real discrepancies/misunderstanding about polycultures and the research papers that are quoted as ‘proving’ their effectiveness, but we seem to stop at the mention of paper rather than really read it, and pick it apart.
      Hope all is well with you
      Deano

      Reply
  8. Dr Ross Mars

    I have never taught ethylene cycle in any of my courses or books. It is during my research into my next book (tentatively titled A Permaculture Resource Book – strategies, techniques and skills for the transition to a sustainable world) that it again cropped up and I looked into. There are many permaculture myths that need debunking, so I am trying to only present scientific fact in this book. Dynamic accumulators is another issue. I used to teach this! I didn’t find any scientific proof, contacted Robert Kourik some time ago, and he sent me his updated version, expressing the view that he wished he had never included that chart. I can’t find any people who are investigating dynamic accumulators so this work will have to be undertaken sometime in the future.
    Anyway I hope to have the book out in March and launch it at the next Australian permaculture conference (APC12) in Tasmania.

    Reply

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