Category Archives: Permaculture

Articles and Links about Permaculture, and my Permaculture Design service

UK Permaculture Convergence 2014

I will be attending the UK Permaculture Convergence 2014, where I will be giving a talk about my work on grain polycultures. The Permaculture Association organises a convergence every two years. The 2012 convergence was the first that I attended, and I spoke about grain growing there too. I have found the two year gap between convergences is really interesting, as it highlights how much has changed in the two year period, a fact that might not have been so marked with an annual event. Those changes will be reflected in the content of my talk.

My 2014 Convergence Workshop

In 2012 my workshop reflected where I was at the time with my Small Scale Grain Growing. Things have changed markedly since then. I have successfully added soybeans and edible lupins to the crops grown, and this year I am growing rice, teff, proso millet, foxtail millet, grain sorghum, grain amaranth, and lentils to see how they perform. Perhaps the best way to illustrate the difference is by the work that I was doing today. Having harvested my wheat, spelt, and rye last week, I was preparing one of those beds for sowing the next crop combination. In this case a second flint corn, to be intercropped with winter wheat, sweet clover, and persian clover. In October the corn will be replaced by broad (fava) beans, and it has been planted at a spacing that will suit the beans. I am looking to use this type of intercropping and follow on cropping to maximise the amount of root exudates produced by the plants, along with the biomass, in order to build soil fertility at the same time as providing food. The adjacent bed is growing grain sorghum, intercropped with grain amaranth, and some white clover and red orach volunteers. I am trying a cowpea interplanting with this combination, to be sown tomorrow, after germinating indoors since Sunday.

To get to these beds I had to walk past a bed with a lentil, soybean, and teff polyculture planting at one end of a bed that included two types of oats, a barley, and a second lentil variety at the other. All very different from the wheat/clover/bean combinations of two years ago.

Workshop Details

My workshop is officially called ‘Designing Grain Polycultures for Food, Fertility, and Fun’ and for the promotional ‘blurb’ I’ve described it as:

‘How complex mixtures of grains,  pseudograins,  and legumes can be grown to feed us and our soils. The talk will include details of the full range of crops that I am growing, including uncommon grains, and legumes, how they effect the fertility of the soil, and how they can be used in multi-species mixtures to meet specific needs.’
What I hope to do is weave together strands of food production, soil fertility, and good design, as well as having a giggle at the same time.

Convergence Highlights

Whilst I’d love my workshop to be the highlight of everybody’s UK Permaculture Convergence 2014, the reality is that there are a lot of good things going on over the course of the weekend. What I enjoyed most about the 2012 convergence was the opportunity to meet in person many of the people that I had been communicating with digitally for the previous year. For Diploma apprentices there is an annual Diploma Gathering, held November/Deacember each year, and there are now more regional gatherings being organised, but this is the ‘biggie’, and a real opportunity to start embedding yourself deeper into the wider network. I am fortunate to enough to be on the panel for Jan Martin’s Diploma Accreditation, which will be held at the convergence. For anybody who wants a chance to find out more the diploma, this is a great chance to listen to somebody explain what it was like for them. You can find out more about Jan’s Diploma on her blog, ‘The Snail of Happiness‘.

Good food, good company, bar, workshops, Diploma presentation, Ceilidh, time and space to chat. What isn’t there to like about a weekend away with like-minded people?

International Permaculture Convergence UK 2015

The UK is hosting the International Permaculture Convergence in 2015, and we will be hosting hundreds of permaculturalists from around the world. The UK Permaculture Conference 2014 is being held at Gilwell Park, which is the same venue as has been chosen for IPC UK 2015. Not only does this give the IPC planners a chance to test out the venue, but it also gives us a chance to get a feel for what it will be like next year. Funds raised from the 2014 Convergence will help pay for the IPC in 2015, so the more people who attend, the easier it will be to fund the IPC, and the more cash will be left over to help funf IPC 2017, which will be in India.

UK Permaculture Convergence 2014 Details

The UK Permaculture Convergence 2014 will beheld at Gilwell Park from the 12th to 14th September. Details and booking information can be found here. The convergence is open to non-members of the Permaculture Association for the first time this year, but the cost for non members is more than the cost of a year’s membership and the price for association members. So it makes sense to join.

Hope to see some of you there




Wolds Woodland Farming Project Open Day

The Wolds Woodland Farming project is the ‘official’ or business name of The Sustainable Smallholding, and the name that is used for the Permaculture Association LAND Project. The association asked for as many Land Projects as possible to open for International Permaculture Day, which is Sunday 4th May. So the Wolds Woodland Farming Project will be having an open day, completely FREE of charge.

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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.


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.


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.






Observe and Interact – Part Two

The Permaculture Principle Observe and Interact gives me a great excuse to bring out the ‘mad proffessor that seems to direct much of what I do. I love to read about a new technique, or in the case of this post an old technique, and then ‘play with it’. Yesterday I did just that with an experiment in Soil Fertility and burning.

Biochar, Burning Wood and Terra Preta

I have done a lot of reading on Traditional Agricultural practises. One technique that is or has been used all over the world is the burning of wood prior to planting crops. This is normally associated with swidden (slash and burn) agriculture. We have an image of indigenous people destroying forest to grow crops, depleting the soil of nutrients, then moving on. The reality is that this is a sophisticated way of farming that uses a period of building soil fertility under trees, and then using that fertiltiy to grow crops. In many ways it resembles the old English Two field rotation. One year crop, one year fallow. In fact it isn’t that long since the burning of stubble in grain fields was made illegal here. What I’ve also read is that in India the wood was slow burned, or charred, rather than burnt fiercely. This throws up some interesting possibilities to observe and interact .

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Observe and Interact Part One

Observe and Interact is one of the Permaculture Principles promoted by David Holmgrem. One interpretation of this principle is that we observe what we see around us, and then use that information to help us to create or modify systems in our designs. However this only touches the surface of what Observe and Interact can help us to do. I try and use this principle with everything that I do Including my reading and research. This post is about the conventional use of the Observe and Interact principle, and will be followed by Observe and Interact -Part Two, which will focus on reading and research.

Eleagnus ebbingei planted in my Forest GardenEleagnus ebbingei planted in my Forest Garden


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