Forget the expensive wetting agents and don’t just chuck that poor soil out, even the driest, nutrient devoid soil is worth saving. Improve poor soils for free!
You don’t need to do a large area at once, in fact I advise against it! Start small and stagger your plantings. This keeps it manageable and allows you to use your household waste as you make it.
So let’s get started! Let’s make this a well-structured earth worm mansion! I’ll update you in a few months to see how it’s going and with my trusty (or maybe a bit unreliable) soil testing kit I’ll compare the results.
Ingredients
When soil is right it is like a rich chocolate cake: moist, dark brown, slightly crumbly, with just the right amount of air and of course teaming with worms, haha just kidding!
So here are my ingredients for chocolate cake soil, like all recipes if you know what each ingredient does you can adjust them to you (or your soil’s) tastes.
Organic Matter, Mini Swales, Water & Clay, Pioneer plants, Green Manure, Mulch, Chop & Drop, Perennials
Organic matter – a little bit of give and take
My soil is just fill dumped by the council when they fixed the sewer line. Grey, devoid of earthworms, dry and fine as ash. It needs organic matter to provide food and habitat for beneficial microorganisms which make their stored nutrients available to growing plants. The term “acts like a sponge” is thrown around a lot in permaculture, but there is no better way of describing how organic matter helps to hold moisture in the soil.
Organic matter comes from the remains of organisms such as plants and animals and their waste products (not human waste products like old TVs, we’re talking manure, but don’t go using human manure either as like dogs and cats they contain way too many nasty bacteria.) I have a bucket in my kitchen where I put any household organic matter that won’t attract rats. So no fruit or cereals which go in the compost, but yes to: torn up paper and cardboard, leaves, flowers, coffee, tea, hair.
This is the lasagne or bolognese method for creating a no-dig garden with an optimum carbon to nitrogen ratio. I’m pretty casual about it (no calorie counting here), I just make sure I don’t put too much chunky carbon dense material in the garden beds I want to plant straightaway as this would bind up nitrogen as microbes try to break it down.
In the urban jungle there is quite a high risk of soil being contaminated whether it be from lead paint flaking off old weatherboards or the dodgy guy who used to strip car bodies in the backyard (no kidding this was what Dylan’s neighbour did along with other unsavoury activities). This is more of a problem for your leafy annuals and root crop where the soil might linger on the vegetable. Fruits have low levels of lead intake so this is what I’m mainly going to grow in this garden bed (fruit trees, tomatoes, eggplant, capsicum, beans, peas). Adding organic matter has also been shown to reduce the lead contamination in plants.
Step 1
So I empty my household organic matter in a bucket, mix in some chicken manure and steep in water for three days, stirring every day to keep it aerobic. If I have excess micronutrient accumulating herbs / compost activators growing I throw some leaves in too. Some examples of these are comfrey, yarrow and tansy. This soaking is like a lazy man’s liquid fertiliser and soften and saturate the dry high carbon materials like cardboard so they breakdown easier, moisten the soil and don’t fly all over the garden (learnt this lesson the hard way when a wind tossed shredded paper all over the garden so it looked like the Merri Creek after a storm). I empty my organic matter brew into rows about 60cm apart on top of the soil where I will plant my first plants.
mini-swales – water retention on a small scale
Like straight lines, perfectly flat surfaces are more of a human thing, and I can attest to the fact that a flat raised garden bed of hydrophobic soil + water is like watching oil rolling off glass! So we need to mould the soil to slow down, capture and direct water where it is needed so it is absorbed not lost whether from the hose or the sky.
Swales are often associated with large scale sloping sites to harvest run-off but can also be excavated hollows in flat lands and right down to the scale of an urban garden.
Step 2
So I added some “mini swales” to capture and slow down water to store it in the soil. I dug trenches between by rows of organic matter and mound the soil on top of them. The roots of the plants I grow on these mounds will not reach the organic matter until they need it and it has had some time to decompose so the nutrients are available. I make these trenches much larger than they need to be to capture water because I plan to build soil up in them to plant perennials in a year’s time, but we’ll get to that later.
Pioneer plants – weeds and succession
So let’s look to nature again, it’s not such a bad mantra. Bare earth doesn’t stay bare for long, where humans have interfered, along roads, eroded river banks and piles of dirt on building sites weeds set up camp and flourish. Living things want to survive and multiply so even under the harshest conditions some plants have learned to adapt so they can colonise even the most unappealing patch of earth. You can actually work out what kind of soil you have and its deficiencies by what weeds self-seed there.
So the tough “weeds” grow first, they mine deeper into the soil getting nutrients which they return to the surface when they die and drop their leaves. Their roots also make pathways for water and air whilst protecting the soil from erosion; in doing so make it habitable for a plethora of microbes, fungi, earthworms and other life which improve the soil further.
Once the soil has been improved other plants will start growing there and eventually these “weeds” will be shaded out as a forest grows.
Deep green permaculture has a great article explaining succession. As well as using this as a tool for preparing the soil for trees, it can also be used as a way of controlling weeds. Here David Holmgren discusses usingshade to control blackberries.
Step 3
So I have transplanted some dandelions, nettles, clover, yarrow and globe artichokes in the mounds. I will let the leaves from these plants fall as they would in the wild to return the mined nutrients to the topsoil. I’ll slash them before they set seed as I have no shortage of these pioneers.
For heavy clay soil:
If you have the opposite problem to mine, heavy clay soil, spike rooted plants such as globe artichokes (cousin of the thistle) and comfrey are good at creating air and water pathways through soil.
Clay
For dry, hydrophobic, sandy soil adding organic matter may not be enough. In fact some decaying plant material such as that of pulses (grain legumes) create waxy, water repellent residues that can coat coarse sand particles.
So what is the opposite of sandy soil? Think about clay soils, they are nutrient dense, sticky and store water. The negatives of clay is that it can hold too much water and drown plant, it swells and contracts which can damage fine roots and can be hard for roots to penetrate at stunting growth. Combining the two creates a friable soil type that is ideal drainage, trapping nutrients and deep straight plant roots, this is called a “sandy loam”.
So how do you add clay to sandy soil? The answer may already be under your feet.
Step 4
I used clay / water mixture to line the bottom of the swale trench to further slow down water drainage and improve water holding capacity of the soil. Below is the process, it’s very simple.
For heavy clay soil:
Organic matter and deep rooted perennials are very important for improving clay soil, but some times you have to resort to gypsum, but beware it can cause more problems if you don’t use it correctly.
First – source it
Luckily where I am the subsoil is clay so if I dig down far enough I can easily get 1kg of clay. It’s pretty obvious when the soil changes to clay, it sticks together more, is often yellower and when you hit it with a trowel it comes off in chunks rather than crumbs. If you want to test though, mix the soil with a little water than roll it in a ball, you should be able to toss if from hand to hand even if it is sandy so don’t be fooled. The next step is to roll it into a sausage like dough, it should hold together well if it is clay and get a smooth quality to it. If you are then able to loop this sausage into a ring then it has a high clay content. Sandy soil will just break apart.
If you don’t have a clay subsoil, ask your friends for a spade full. You can find out the location of Austalian soil types at ASRIS website.
second – soak it
For 1m2 soak about 1kg of in a bucket of water for 24 hours to absorb water and break up large globs. It is easier if you dig it up dry as it sticks to your spade wet, then with a trowel, then gloves break it into crumbs. Once under water mix it so nothing sticks to the bottom. Any rocks will sink, organic matter will float. Skim the organic matter off as this will clog your watering can.
third – mix it and decant
Mix it so that the fine clay particles are suspended in the water (looks like chocolate milk shake) and decant into a watering can. Leave any solid muck that isn’t suspended at the bottom and fill with water again and give it another mix.
fourth – water sandy soil
All you need to do is increase the clay content of the sandy soil by 5% for it to improve water holding capacity so no need to over do it. I filled the trench with a watering cans worth of clay solution mixing in the soil removed from the trench. I refilled the watering can and repeated until only rocky dregs remained in the bottom of the clay bucket and all the displaced sandy soil was mixed in. You could also just pour the water out of the bucket for less even, but faster method.
The soil should no longer be hydrophobic and be able to retain nutrients from organic matter.
And as an added bonus the left over sand you have can be used in homemade potting mix!
mulch
In the bottom of the trench I am going to place more organic matter as a deep mulch. This won’t be planted out for a year when the soil is more stable for perennial fruit trees and shrubs. While the organic matter is being decomposed the soil is going to settle a lot which can damage delicate roots and I plan on adding more dense carbon matter in the trench which is good for drainage but may decrease the available nitrogen while microbes break it down.
Charcoal from wood burned in our outdoor stove is one of the things I will be adding the trench. In his book Woodsman, Ben Law says the benefits of Biochar include: improving water holding capacity, allowing microbes and fungi to colonise, porous structure traps nutrients, helps prevent greenhouse gases escaping the soil.
Here are two interesting articles about Biochar, one questions the benefits of Biochar suggesting it might actually reduce nutrients in the soil and that on an industrial scale could be as harmful as biofuels. The other suggests that combining it with high nitrogen/liquid will help unlock the nutrients sooner. As we just burn prunings rather than deforesting forests a little bit of charcoal should be fine, better in the soil with a chance of improving it than in landfill.
If you make a trip to the beach, seaweed would also be a welcome addition to the mix to up the micro-nutrients.
Step 5
For the trench mulch I fill a bucket with more of the household organic matter and chicken manure to balance out to the high carbon charcoal, of which I add sparingly. I then fill the bucket with water as before, stirring daily. After three days the charcoal should be “charged up” with nutrients and saturated with water, ready to add to the bottom of the trench. I suppose if I soaked the charcoal in urine it would be even better, but for now I won’t offend the delicate sensibilities of my neighbours.
green manure & chop & drop
I’m sure by now you know the benefits of green manure, but if you need a refresher here is a great link to one of my favourite seed companies Green Harvest.
As you would find on the forest floor a mulch of fallen leaves helps keep moisture in the soil and provides habitat for top dwelling organisms. Here is a little bit about the chop and drop method of mulching.
step 6
I sow green manure on the top of the mound to act as a further living mulch to protect the soil from nutrient loss and stop erosion. Once the green manure has grown tall and before it sets seeds I slash it and the other “weeds” and use the leaves to mulch the soil whilst leaving the roots in the soil so as not to disturb it. As these are annuals they won’t continually resprout, the stems and roots will decompose and add nutrients back into the soil.
perennials
I’ve already touched on how perennial plant root systems mine deep to bring nutrients from the subsoil and hold the soil together. They are generally more resilient than most annuals to extremes and fluctuations and most importantly low maintenance and once established high yielding.
step 7
Once the green manure is cut back I will plant perennial herbs and small fruiting shrubs and berries on the top of the mound. When I transplant them I add some worm castings and/or mature compost to the hole to give the plants a little boost. Worm castings are also meant to “act like a sponge” to improve water holding capacity.
Next autumn when deciduous leaves drop I will plant some bare rooted fruit trees in the swale trenches. I will continue to mulch with household organic matter and chicken manure, but the ultimate goal is to have a food forest system where understory plants are a living mulch and companions to the fruit trees.
Other amendments
As I wanted to provide you with a free method of improving your soil without having to buy anything I didn’t include the following, but by all means go for it if you feel your soils needs that extra helping hand.
Mycorrhizal fungi – the symbiotic relationship between mycorrhizal fungi and their host plans is really fascinating and I invite you to read more about it in these article. These fungi occur naturally in healthy soil and form a kind of extension to plants roots.
You can buy packets of this at nurseries, all you have to do is dig the roots of plants you are transplanting in the powder.
Rock dust
Ground up rocks to add to depleted soil which normally could only be accessed by deep rooted trees mining deep into the soil. Aside from adding these essential minerals it is also purported to help retain water.