How to make healthy soil – transforming dirt into soil

There are several key things we need to consider when we’re looking how to make healthy soil from a soil that is more like dirt.  Is it even possible?  When we talk how to make a healthy soil, we’re talking about transforming a poor soil or dirt into a healthy soil.  Making healthy soil is a relatively simple process. It does however take a bit of work, a bit of science and a bit of time.We can think of dirt as soil less the abundant life. It’s relatively lifeless compared to soil. There are microbes in dirt. Dirt that you find in nature isn’t necessarily sterile, but the quantity and diversity of bacteria, fungi, protozoa etc are low. In contrast, soil, fertile soil is abundant with microbial activity.

Healthy soil has a massive population and an expansive diversity of microbial life. Soil microbiologist Dr Elaine Ingham says the more diverse our microbial population, the better the soil.

Now, there are different kinds of dirt and different kinds of soil. There’s clay dirt, sandy dirt, rocky dirt… Using similar techniques we can make a clay soil, sandy soil etc.

This blog will be a discussion of transforming dirt in general and how to transform it into a soil, generally. Discussions for transforming specific kinds of dirt into soil will form other blogs.


What do we want?

The first question I always ask before I start transforming dirt into soil is: What do we want to transform this bit of earth for? What’s the purpose? The reason we ask this question and the answer we give will influence how we transform the soil.

Generally speaking, how to make healthy soil for an edible garden is different from how to make healthy soil for ornamental shrubs.

If we want to create an edible garden, we’ll want high fertility and a healthy habitat for lots of beneficial bacteria and worms.  However, we must note that some edible plants won’t thrive in highly fertile soils.  So, like always, there are exceptions to the general rules.

Creating soil for a forest requires lower fertility and we’ll need to create habitat for lots of fungi.  That’s because trees generally prefer a fungal dominated soil.  Again, there are exceptions.

Making healthy soil for the purpose of lawn, we’ll want a different mix again. So for that reason, well make this discussion general and allow space for other blogs to be more specific.


Dirt needs life

Generally speaking, when I come across dirt, I come across dryness. That’s one of the first things I notice. It tends to be dry. Let’s assume there’s been rainfall or watering.  We’ll assume the dryness isn’t due to water being withheld.

Given that, the dirt might be dry because it’s hydrophobic – repelling water – or it could be dry because there’s nothing of substance in the dirt to hold moisture in. Alternatively, the dirt particles might be so compacted together that moisture just runs over the surface rather than soaking in.

The cause of these problems is different from each other: the remedy is similar. The hydrophobic soil is more likely to be a sandy soil or a soil that’s had a pine based mulch applied to it.  For more on hydrophobic soils read my blogs: Hydrophobic soil: what is it and what does it look like; and Dry pot plants: fixing hydrophobic soil in pot plants.

Where the soil is dry because it lacks moisture retaining substances we have a lack of clay and/or a lack of organic matter.  A lack of organic matter will cause a lack of microbial life.  We start to see the cycles and how conditions affect each other.

A compacted soil is more likely to be a clay base. This is because the structure of clay particles are flat like tiles.  They fit neatly together one upon the other and they can prevent oxygen and water from adequately penetrating the soil.


How long have we got?

Another thing to think about before doing anything is: how long have we got to make this healthy soil? Do we need it transformed for planting in a week, or a month, or a year? The answer will impact our method and our wallet. It will also impact the quality.

It takes time to make healthy soil. We need microbes and worms to do most of the work and for that we need to create a habitat for them to live in. That’s what we’re doing, habitat creation.  We’re trusting the rest of the process to nature.

The more at home the soil life is, the better the plants will do there.  So if we’ve only got a week, then the transformation will be minimal.  There are things we can do to speed things up, but they can also have devastating consequences.  For example we can add a diluted molasses solution and generally that will be a feast for microbes.  However, it’s a feast for all microbes, particularly bacteria.

We can imagine that if we have too many pathogenic bacteria, then the molasses will feed them.  As a result, they’ll flourish and set back our soil transformation or completely ruin the soil for a time.  It can make our soil anaerobic and toxic to plants.  Therefore, such speedy solutions should be used with caution.

Another determining factor here is: what season is it?  Most microbes will be asleep and dormant in the winter.  They’ll be fully awake and active in the summer.   So it follows that soil transformation occurs more rapidly in the warmer months compared to the cooler months.


To till or not to till, that is the question.

Tilling soil is a process of breaking the surface and turning or breaking up the soil. There are arguments for and against tilling. Tilling releases nitrogen and other gases into the atmosphere.  This process further depletes the soil. It also breaks microbe communities and strands of fungi and can injure earth worms.

Many Buddhist practitioners don’t feel comfortable tilling the soil.  So I don’t tend to till soil. But we aren’t talking about soil, we’re talking about dirt. There aren’t many worms in dirt. So I say: till it!  Carefully…

Depending upon the purpose of the soil transformation – what we’re going to plant – the depth we need to dig to will vary as will the width. For an edible garden a good rule of thumb is to dig at least to the depth of a shovel blade… that’s about 30cm.

For shrubs and trees we should dig twice that depth and a corresponding width.  Even if the shrub or tree we are planting is still in its little tube stock pot… give it a chance and prepare the soil for the developing root system.

I like to break the ground up into large chunks first and then sit down and start breaking it up with my bare hands or if the soil is really tough, with gloved hands.

With my bare hands I come into direct contact with the dirt.  I can feel it fall apart or grip together. I can feel its resistance and its general vitality.  Working so closely with the soil we can also safely release any worms and reduce injury to them.  This is very important to me.

We can get rid of weeds and bits of lawn and rock and crumble the usable bits back into the hole. This process takes time. It’s a process of mindfulness. It’s a meditation and a connection with the earth.

Breaking up a clay soil like this speeds up the transformation process.


Soil type

Once we start breaking the dirt and letting it drop back into the hole we have a pretty good idea whether we’ve got sand or clay.

If our soil type is clay it’ll be fairly difficult to break the chunks apart. Clay can perform like concrete and it can be really hard to break apart. If you’ve got clay soil, you’re going to need to bring river sand in to aid the transformation process.

If your soil type is sandy, it’ll feel sandy and gritty and it’ll tend to fall apart really easily. It could have rocks in it and the sand particles could be really small. But compared to a clay, it’ll fall apart as the soil particle cohesion is much less for sand.

Transforming a sandy dirt into soil requires clay and organic matter.


Soil texture and structure

We want our soil to have a texture that is fairly soft to the touch and a structure where soil particles hold together well but also separate under a slight pressure.  When we alter texture and structure, we alter the basic components of the soil but not the basic soil type.

So for clay that has a particle structure that is close knit and slots together evenly, we need a gritty substance like sand to roughen the smooth plates of clay.  Imagine clay particles like small tiles.  They fit together in a close knit fashion.

Generally speaking, to transform clay we need to add the same amount of river sand. Sand also helps earth worms digestion processes.

Sandy soil particles are larger and jiggered in shape and they don’t tend to fit together nicely. There are large air pockets between the particles and this is what makes sandy soil so well draining.

The texture is rougher and if falls apart easier. We need to soften a sandy soil and we need to close some of those air pockets with smaller particles. We do that by adding clay and organic matter.


Soil pH issues and adjustments

If we know the pH of the soil then great, if not, test it. I’ll write another blog on testing and alter the soil pH but at this stage, if you don’t know the pH don’t stress about it. The microbial community will eventfully neutralise the soil.

In my experience however, most clay soils are acidic, particularly here in South Eastern Queensland. My place has clay soil with a pH of 5. That’s pretty acidic and I’ll want to neutralise that. Likewise, I haven’t come across many alkaline sandy soils but it happens.

Soil chemistry is very complicated so I don’t advocate for using lime, dolomite or sulphur unless you know the chemical make up of the soil.  We can adjust the pH using organic matter.


Adding organic matter

Organic matter forms the main diet for the microbes and worms. It aids with water infiltration and retention and adds vital nutrients (micro and macro) to the soil and soil life.

Mushroom compost tends to be really alkaline and has a pH of about 9. That’s really high. To neutralise an acidic soil we just add some mushroom compost.  That will start the neutralisation process.

I don’t tend to add manures straight to my soil.  Composting them first feels right for me, personally. I feel that if the worms have worked the manure over, it’s safe for my garden.  If not, there might be pathogens and that doesn’t really interest me.  Hot manures like horse manure should be composted for 2-3 months regardless.

If you have a compost heap it’s likely that its got worms in it. Mine certainly does. When adding this worm laden compost, I tend to do it last and I don’t mix it in as that hurts the worms. I simply add it to the mix handful at a time. The worms will mix it in over time.  However, I can only compost enough for my edible gardens.

I use a manure based compost from the local landscape suppliers to transform all other soils.  I’ll often add some of this to my edible gardens and new gardens I’m creating. The worms and microbes love it and it mixes well with what we already have.


Adding other minerals and nutrients

Rock minerals is another key ingredient when we’re looking at how to create a healthy soil.  Rock minerals add vital micro nutrients to the soil.  The amount we add depends on how much soil we’re transforming. A rule of thumb I guess might be: A small amount, a sprinkle.  Another rule of thumb is to read the label..


Finishing touches

Once we’ve done all that we need to cover the soil with a suitable mulch and water it in. In order to help maintain the microbe habitat, we need to keep that soil moist. Not too wet, not soggy, moist. The amount of water to add over time will very much depend on our wider environment.

If you want to plant edibles, you could plant now but don’t expect to get awesome results in the short term.  An edible garden will do better once the soil mix is full of worms and microbes. That’ll take a bit of time but if we’ve served up the food they like, they’ll feast and reproduce in a flash!


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