CompostSoil Rehabilitation

An Experiment with Soil

Beginning to plant a garden in poor soil is probably guaranteed to disappoint, but what’s the most effective way to create a good environment to give your seedlings a head-start? I embarked on an experiment to see if I could find out. Join me, if you like, on a voyage of soil discovery.

Choosing my Methods

My desire is to avoid chemicals where it is possible (indeed, usually the natural alternatives are more effective anyway).

Also, my budget for this experiment was zero.

Bearing these two factors in mind, I looked around for what I could find to help improve the soil.

The specifics of the garden are: it is at 900m in a Mediterranean (Spanish) climate, which I think roughly translates to USDA Hardiness Zone 7 or 8.

It is in three sections, so I chose three different methods to compare:

  • The first section I decided to plant straight into the ground, and sow seeds of nitrogen-fixing and soil improving plants thickly around the main crop plants.
  • For the second I used manure, collected from the sheep of a neighbour.
  • And the third — sheet mulch with the plants planted through a layer of cardboard to suppress weeds.

The Aim of the Experiment

I don’t know if ‘experiment’ is the correct word, scientifically speaking, as there are of course many factors affecting the result, not only soil.

However, the idea is to plant more or less the same combination of plants, at the same time, into three different sections of garden — one with sheet mulch, one with soil-improving plant friends, and one with sheep manure.

I will then observe how the plants grow to see how successful each of these are at providing happy, healthy homes for the plants.

Ways to measure this include:

  • Comparing the size of the plants
  • How fast they grow
  • How healthy they look

The three components in more detail

Manure: from the earth-floor of a sheep-pen. This I broke up into small pieces and mixed into the top few centimetres of soil.

Mulch: normally for sheet mulch I will throw in whatever organic matter I can find, but for the purposes of experimentation I kept this one quite simple.*

  • A layer of chopped plants: vetch and clover (nitrogen-fixers), dandelion and borage (deep tap roots: dynamic accumulators), and some fennel (insect-repellent properties)
  • A layer of dead leaves, sticks, bits of bark (carbon)
  • A layer of ash
  • Cardboard on top, covered with a layer of forest soil (rich earth from under brambles/trees)

*One thing I did not use is grass, as I have some experience of using dry grass as mulch, where the garden ended up more like a meadow…. I forgot about the grass seeds!

Plant friends: sowed lentil and fenugreek seeds very thickly around the entire section. Also planted some peanuts around the bed (all nitrogen-fixers).

In all three beds I sowed mustard as groundcover to discourage unwanted ‘weeds’ (although of course depending on your view, there is no such thing as weeds, only plants in the wrong place…).

My predictions

I predict that the most successful bed will be the sheet mulch. Why? Because I feel like I have put in a healthy mix of nutrients into the soil, ready to feed the new plants all that they need.

The manure may also provide a healthy nutrient mix but I didn’t get to see each component going in, so to me it doesn’t feel so effective.

And the plant friends? Although I have had success with companion planting before, I really have no idea how it will work in the first stages of the garden’s life.

We shall see…

Two weeks after planting

Very markedly different things are happening in each bed.

Manure bed: Here the plants look for the most part happy, although they have not grown much (in comparison with the friends bed).
Also, some have turned red or have red spots on their leaves. Possible explanation: the manure is too strong for them and they are getting burnt?

Friends bed: Here the plants are looking bigger and healthier. Most of the groundcover has sprouted and is doing a good job of coverage (more so than in the other two beds).

Sheet Mulch bed: Here the cardboard has not been very successful at decomposing, even underneath the soil layer, and most of the transplants here are dead.

None of the seeds have sprouted.

My conclusions

It seems that less is more: the bed in which I planted seeds straight into the ground did the best, while those which I added additional elements fared less well.

This is by no means conclusive and I will be conducting more experiments to test this theory.

One possible explanation I have for why the plants in the sheet mulch bed were so unsuccessful is the aridity of the climate. Although I was watering the sheet mulch bed daily, the general dryness of the air meant that the cardboard took much longer to decompose than other sheet mulch beds I have created in the significantly more humid climate of England.

This observation is an important one to remember and I will consider more carefully how to tailor my methods to the environment in future.

Whatever the climate where you are, I hope this has been a helpful experiment and don’t hesitate to make your own investigations!

Charlotte Ashwanden

Charlotte Ashwanden (nee Haworth) I got my Permaculture Design Certificate in 2011, from Treeyo at Permaship in Bulgaria, and since then have been traveling the world learning about and practicing permaculture. Born in London, I've lived in a number of places in England, Spain, the Basque Country, and Italy. My mum lives in Leipzig (Germany) so I've spent some time there. In 2015 I got married in a pagan ceremony in a field to David Ashwanden and changed my surname to Ashwanden. A professional dancer, I do fire and hula dance and have recently become interested in dance meditation. Currently, I live in Thailand in a Forest Buddhism community school, so you can expect lots of tropical permaculture related articles in future.


  1. Hi Charlotte – such experiments are worth trying and sharing.

    Just a couple of thoughts:

    1. Manure needs to be composted before putting into the garden, or, the manure can be put directly into the garden and then left to ‘cure’ for a season (how long really depends on how alive/active your soil is, as well as moisture and temperature levels) before plants and seeds are put into it. (i.e. worms, microorganisms, etc., will break it down if given time to do so).

    2. In similar but different fashion, sheet mulch can also need time for curing. Microorganisms in the soil will attempt to break down the high-carbon cardboard, and they use nitrogen to enable them to do this work. This, thus, can take nitrogen away from plant roots until the cardboard is sufficiently broken down. It’s called a ‘nitrogen drawdown’. You can minimise this effect, or eliminate it, by putting a layer of well broken down compost under your cardboard layer. Or, as you say, it may well be just because the soil is too dry, and your water is not penetrating sufficiently to reach the plant roots.

  2. My experience has been that cow manure works really well. I use heaps, mix it up, and then wait for the weeds to sprout, once the weeds are sprouting (about a month) I know it is ready, then I just hoe and plant.

  3. Hi Charlotte. You are a natural scientist. It is good to read about techniques, try stuff out and observe how it performs in your environment. Well done.

    I’m also in a Mediterranean climate, but down under. Like you, I find that cardboard takes so long to break down that it becomes a serious fire hazard over summer. Not good.

    As a suggestion – and some people here are not going to like this at all, but – burn off your paper and cardboard (safely in a controlled environment) and then spread the resulting ash thinly about the place and water it in. Don’t do it too much or too often as it raises the ph of the soil. Cardboard is really high in boron which is an essential plant element for growth. Don’t spread it around on a windy day as you’ll lose most of it! Less is more with ash.

    If you are a bit tight for cash, get imaginative and compost every scrap of organic matter that comes onto your property. Try composting your own poo too as it is a good source of cheap fertiliser. Look into all of the warnings though and use common sense and you’ll be fine.

    Unlike a lot of other animal manures, sheep poo is kind of dry. I don’t have access to it, but if I did, I would add it to a pile of woody material, water it (if you have the spare water) regularly and let nature do its thing, then use it. Or you could add such a mix of materials around the drip lines of fruit trees and then not think about it again.

    The meadow is not a bad idea, especially if animals graze it. Chop and drop is good on a meadow too. It is pretty low stress and you can always plant it out later.

    I look forward to seeing how your systems progress as time goes on.


  4. Our property and hence our vegetable garden/food forest is on pure deep sand. When I say sand, it is relic ancient coastal dunes. There is no organic matter whatsoever. However in just one year we can achieve incredible improvement in the soil with good rich organic layer forming and a multitude of worm activity.

    To start a new patch we put down cardboard in a single layer straight over the sand and any weeds growing. Then on top I throw at random the following stuff on a regular basis and when I have access to it (usually through the winter and early spring):

    soiled straw and shredded paper and poultry manure from the chicken and duck coops. I do not ‘age’ it or compost it. It goes straight on. Cut grass, normal compost, ash, cut down borage, lucerne, comfrey,rocket plants after they finish flowering, horse hair (from clipped racehorses), horse manure (fresh/old), cow manure (fresh/old), bark and wood shavings/chips from the firewood chopping area, pea straw, waste from the guinea pigs.

    I plant stuff straight into this, making a hole in the cardboard if it has not broken down completely. In a matter of weeks or a few months the worms are going crazy and the top of the soil is becoming dark and full of broken down organic stuff. In a year you have a few centimetres of soil instead of sand. Each year I repeat the process and the layer gets deeper. Works for us, we have great success with our vegetable and herb garden. :)

  5. Plant into aged horse manure beds… as in, put them on the ground (skim grass off or existing soil) and during your fall align the areas you want to do and layer materials… plant the following early spring…a sure fire way for it be ready…

    Enjoy –

  6. I’d change the order of your sheet mulch. Cardboard first to suppress whatever plant growth the existing soil might produce, then a mixture of green and brown with a bit of forest soil mixed in to help it decompose faster, then 3-4 ” of forest soil. No ash without a soil test since ash will raise your soil pH and tie up phosphorus, iron, boron, manganese, copper, zinc and potassium. Ideally, you’d like a slightly acidic soil somewhere between 6.0 and 7.0.

    As your seedling emerge, start adding mulch. Continue to build it up as they get larger. This will retain water and shade the soil around the plant roots. The “edge” between the soil and the mulch will come alive as the mulch is turned to compost.

    I’d also implement a programme of continued soil improvement by planting nitrogen fixers such as peas and chopping and dropping them before they start to flower (allow a few to go to seed so that you have seed to continue the programme) so that the maximum nitrogen is retained in the soil. Plant into the dropped material.

    And mulch, mulch, mulch. After having performed its weed suppression and water retention function, it will decompose into compost. There’s no need to turn it into the soil since it will turn to soil in place.

    Inoculate your soil or plants with mycorrhizal fungi to assist in micronutrient and water uptake and extend the reach of plant roots. Disturb you soil as little as possible so as not to disrupt them.

  7. To back up what Craig was saying about how too much carbon can draw out nitrogen, when my wife and I started our garden last spring, we had watched the video “Back to Eden” and were sold on the wood chip method. We brought in a truck load of chips and covered all that we’d planted and were hoping for an outstanding garden. In our experience many things didn’t sprout, insects were rampant in the wood chips, and things we’d transplanted grew slowly until the last of the season, when they finally began to flourish. I believe, as Craig said, too much nitrogen was being drawn from the plants by the decomposition of the wood chips. Part of the reason, too, may be that this garden was only established the year before, and was tilled using a rototiller. (We learned afterwards the consequences of tilling and no longer do it) so it is an immature garden and we are building fertility. We did put horse manure on it when we started it, and added more this spring, but I think it will be next season before we’ll have finally built the soil up to point where we’ll have the results we expect. We are raising rabbits now, and have a continuous supply of great fertilizer, so we are optimistic for next year’s results.
    – Joe

  8. There are wood chips and there are wood chips. You want ramial wood chips which are from branches less than 2″ in diameter and you want deciduous not coniferous, ie, hardwood instead of softwood because coniferous are allelopathic; they suppress growth on the forest floor. An excellent discussion can be found in Michael Phillips’ The Holistic Orchard.

  9. Our deep beds (our garden was a builders yard so is mostly broken concrete and gravel) are made from scrounged material. First a layer of cardboard to suppress the weeds, then a layer of turf (readily available from skips where people are concreting over their front gardens!!) then a layer of horse manure (tested by growing a tomato seedling to make sure is is not contaminated with Clopyralid persistent herbicide). Then a layer of scrounged soil and mulch with whatever is available – my favorite at the moment is flax guinea pig bedding collected from someone with over 100 guinea pigs!

  10. As Steve Solomon recommends,
    Soil test, Soil test, Soil test…adding anything without a soil test is like putting one’s hand into the pantry and adding a jar of whatever to the recipe, whether needed or not (vegemite into banana cake? Yuck!)
    Check out Yahoo Groups “Soil and Health”

  11. Hi,

    Nice article, thank you very much for this experiment.

    I do have a question:

    Is ash really all this good to add in a garden? Or even in a compost? I think that it has very good anti-fungi, anti-bacterial properties, but I am not sure. Anyone could tell me more about the subject?

  12. When I was suggesting a soil test, I was thinking of a simple pH test. Solomon is aiming at producing nutrient dense vegetables and has had great results using full blown soil tests but they lead to using significant external inputs which are neither sustainable nor regenerative. If one chooses not to go that route, I’d say build the soil with humus by using nitrogen fixing green manures which you chop and drop; add comfrey, lambsquarter, pigweed, stinging nettle, dandelion to your compost heap since they are excellent sources of the primary and secondary macronutrients and the micronutrients; mulch heavily; and inoculate with mycorrhizal fungi. There’s a good soil overview at If the site is down, try

  13. I really enjoyed this article. Would love to see more regular folks experimenting and posting what they found. I’ve learned so much from this article and the comments then I usually do from books.

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