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…).
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.
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!