A few days ago I blogged about the importance of getting to know your soil, but, as vital as this knowledge is, it’s what you do next that really counts. Once armed with the basics of your soil type and it’s strengths and weaknesses you can then set about planning how best to make improvements.
Loam - the dream soil for any gardener.
You can think of garden soils as being like the scoring areas of a dartboard, with bands and boxes of possible scores representing all the different varieties of soil. Some will deliver a higher “score” than others, allowing you to grow a wider and richer variety of garden plants, but the ultimate goal has to be the bull’s-eye, which, in the case of garden soils, is a rich, crumbly, open, humus-rich loam – think of worm-casts.
The big difference between your garden and a dartboard, though, is that with a little help from you, the trusty gardener, your soil score can be shifted around and boosted in all sorts of ways, and eventually land right on that bull’s-eye.
The general catch-all advice to apply compost whenever you plant anything and to mulch everything once a year is certainly a good start, but it’s by no means the end of the soil improvement story.
Improving soil structure.
The most common soil type is clay based and they tend to be sticky, dense and poorly drained, in extreme cases plants can essentially drown over winter with the roots rotting of into a big wet mush. Improving a clay soil means breaking up that dense structure by creating micro air pockets throughout, which will automatically improve drainage.
Adding compost to clay might help initially, but within a matter of months that organic material will have been thoroughly assimilated and broken down by bacteria and you’re back to square one.
Pea shingle - the number 1 remedy for opening up a heavy clay soil.
The longer-term solution is to add in large quantities of inert, non-organic, (i.e. non break-down-able) material to open the structure and keep the clay particles apart permanently.
Grit and/or pea shingle are what is needed, the exact quantities being dependant on just how much clay there is present in the soil.
A general incorporation of any of these materials every time you dig, plant or work the soil will slowly improve conditions both for plants as well as for worms and other essential soil fauna.
Composted bark.
Beware of adding sand to a clay soil, the particles simply aren’t large enough to open up the dense clay and you’ll likely end up making a kind of home-grown garden cement mix instead.
The next phase in all about keeping a good supply of coarse (and it must be coarse) organic mulch on the soil surface, ideally in bi-annual applications.
Chunky composted bark is pretty much ideal for the task, as is semi-composted leaf mould.
The aim here is not to feed the soil directly – clay soils are already naturally full of nutrition – but instead to feed those worms and myriad soil critters & micro-organisms who will then repay you by working, digging, digesting and opening up the soil 365 days a year.
Improving soil moisture levels.
Light soils – typically sand or chalk based – suffer from the opposite problem to clay soils. They drain beautifully, so nothing’s ever likely to drown, but they are very bad at retaining moisture and gardeners are likely to be forever watering and feeding to keep their plants looking spruce.
Here the non-organic, inert parts of the ideal soil are already present, and you’ll certainly never have to add shingle to a sandy soil, but often the organic elements are sorely lacking.
Humus is organic material that has been digested, and processed by soil bacteria until it has reached the point of stability – in other words it won’t break down any further, but neither will it disappear from the soil. With light soils the aim is always to increase the humus content, which in turn makes for a more porous, sponge-like soil that will retain water through dry spells, but still drain well in the wet.
Leafmould - the most natural of all soil conditioners.
Bulky, organic materials are the solution and your own garden compost is likely to be as good as anything, as well as being chemically harmonious with your garden (since all the leaves and garden debris originated from there in the first place!)
Well-rotted farmyard manure and leaf mould also work well, and other options include old mushroom compost (which is very alkaline) and composted paper, spent brewery hops or seaweed.
All of these should be added as a mulch, where, once again, the worms will do the rest for you.
Mulching has the added benefit of insulating the soil from evaporation and should be considered pretty essential to help conserve moisture levels in lighter soils.
Adding nutrition.
Nutrition is not the same as structural bulk in a soil, although the most useful materials can certainly supply both. Most mulches, though, are not going to do anything for your soil nutrition levels, in fact they may even end up depleting nutrition as bacteria use up nitrogen to break down bulky material like wood and bark chips.
The decomposition of organic matter – be it compost from your garden or manure from a farm – involves several phases, and it’s only during the final phase (when things are pretty much well and truly rotted) that nutrients are released back into the soil in a balanced and useful way.
Horse Manure - well composted and ready for garden action.
Quick fix plant feeds (be they liquid or solid, such as pelleted chicken manure) may feed individual plants but will generally leach away almost immediately and are of no lasting benefit to the general soil. The old maxim of “feed the soil not the plant” is definitely one to keep in mind.
Well-rotted manure (preferably horse, though any large-ish herbivore that you happen to have handy will also supply the goods) is certainly the number one choice for adding slow release nutrition – principally nitrogen – into the soil. Bonemeal is also slow to break down and releases phosphorus as it decays, and wood ash (which like mushroom compost is strongly alkaline) will provide potassium.
Together these are the three main elements for plant growth and will provide the recipe for effective and long-term soil nutrition.
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