The Art Of Soil

Everything you need to know about soil by ANDREW JOHNSTONE, who has been working with this life force for more than 40 years, so he knows what he’s talking about.


Soil is the mix of clay, sand, volcanic ash and humus that lies on top of the bedrock of the planet.

Humus is organic matter – the remains of living things that have fallen onto the ground. This includes dead creatures, their bodily waste and discarded parts, leaves, twigs, stalks and branches, and via the activity of fungi, bacteria, insects, earthworms and the weather it has been transformed into a fertile medium that promulgates life. Good black soil is a living organism, a dynamic place where a vibrant community of creatures turns old life into new life.

With a bit of fertiliser you can grow your vegetables in raw sand and clay but it is difficult for plants to properly flourish on undeveloped soil, which lacks the robust properties of a mature topsoil (including superior fertility, aeration and water drainage and water holding capacity). While most plants can survive on poor land your ability to draw food from them is limited. Food plants need rich, vibrant, fertile soil to produce their best.

In well developed topsoil we find something special happening: the micro-flora and fauna working in symbiotic communion with the cultivated plants helping them to access nutrients and fight disease.

Good quality black soil will pulsate with a variety of species including earthworms. The Tiger Worm just loves fresh organic matter, quickly turning it into nutrient-rich castes that directly feed the plants. Then there are those great big fat and very long worms, which burrow deep into the substrate of your garden soil, mixing the black with the dirt/sand/clay/ash. You will find myriad fungal species in healthy soil, including many types of beneficial fungi that sometimes manifest as fine white threads. These all indicate that your soil is healthy and convivial to life.

You will also find myriad insects scattered about. These are mostly your friends, consuming organic matter and pissing and shitting it out to become food for other organisms to consume – not to forget the benefits their dead bodies offer the soil once their life cycles are complete – but many are also often beneficial predatory species hungry for other insects that might not be so kind to your plants. Get to know about all these creatures and learn to appreciate them. They are part and parcel of the gardener’s toolbox.

Trenching is recommended

You’re on the lookout for anything that decomposes: organic matter. It can be composted and if suitable, applied directly onto the soil. Trenching is another valuable method and one that is in my opinion superior to conventional composting, as it takes place directly in the soil without the nutrient and energy loss inherent in intermediary methods.

Simply dig a shallow trench and apply the material and cover with soil. You can plant directly on top or wait a few weeks until it is has broken down somewhat and become more useful to the plants. If you are planning to plant fruit trees you can work ahead by digging a nice large hole and filling it with various sorts of organic waste and keeping it covered while it composts. Your tree can later be planted directly into this rich new soil where it will thrive.


The gardener’s miracle friend: spent coffee grounds


Sources Of Organic Matter

General Kitchen Waste – Includes bones and plain brown cardboard (toilet rolls and such like as well as absorbent kitchen paper are fine). Bones (a considerable source of calcium, magnesium and phosphate) take a while to break down but you can hasten the process by breaking them up a bit with a hammer or some such. These provide a long-term source of nutrients. Don’t forget to add the dregs of your tea and coffee to the kitchen waste mix. Also wash out your milk cartons, yoghurt containers and tin cans – all this liquid is a valuable nutrient resource. Remember: if it rots or ferments it is soil-making gold.

Ash – If you maintain a fireplace you have at your disposal a handy nutrient- generating tool. Wood ash provides a valuable source of nutrients that includes the essential plant foods phosphorous and potassium, as well as a host of trace elements including calcium and magnesium. Be careful to ensure the wood you are burning is untreated. Commercial timber, as used in the building trade, is treated with various preservative chemicals that result in toxic ash and smoke when burned. Also avoid particle wood, plastics and coated paper and cardboard. All of these contain toxic elements.

Bones break down quickly in your fireplace. Reduced to ash, the nutrient content will be transformed into a method easily accessed by plants. Another handy item for the fireplace is seashells. Nutrient dense but laboriously slow to decompose unless finely ground to the consistency of talcum powder, they quickly fall apart in fire, thus breaking free the rich nutrient content for your lawn and garden. Wood ash is a reliable method of fertilising your lawn and lawn clippings are a valuable fertilising tool for your trees and garden.

Lawn Clippings – You can add to your compost or simply spread them under fruit and ornamental trees and shrubs or place directly on top of your garden soil – this method will assist in moisture preservation. Grass is not only nutrient-rich (depending on the quality of the land it is growing on) but also a decent and handy source of organic matter. Be careful with your clippings if you have used weed sprays on your lawn. Some of these chemicals persist and can build up in the soil and poison your food crops. Tomatoes are especially susceptible to some common herbicides.

Tea Bags – Tealeaves are rich in nutrients and are a decent type of organic matter.

Coffee Grounds – This stuff is nutrient dense and full of carbon and your soil community will go nuts for it. Spread it directly on the soil and around the plants. It also grows great lawn. If using quantities obtained from a café, dump it directly onto the lawn and spread it out with a rake. The grass will grow through it, creating a dense soft sward – become friends with your local café and take all you can.

Coffee beans are seeds and being as such are a dense nutrient storehouse for the new plant. After fermenting and roasting, the ground beans are simply washed once with hot water (to make your brew) leaving most of the good stuff behind for you to add to your garden. There is a myth floating about that spent coffee grounds are acidic and harmful to plants. It is just that: a myth derived from the idea that because coffee tastes somewhat acidic then it must be acidic in the garden. It isn’t. Coffee grounds are brilliant and your garden and orchard will absorb any quantity you offer and love you for it.

Egg Shells – Crush them up and slowly their rich mineral composition will degrade into useable food for the garden. Your local café/restaurant is again a good source.

Horse poo is great in the garden

Poo – Horse, chicken, cow, goat, pigeon and sheep – it’s all good. Spread it out on the soil (or dig it in) after harvesting and cover it with coffee grounds or wood mulch to soak up the odour (this is the ‘carbon factor’ at work). Give it a few weeks and the worms and fungi will have reduced it to rich friable black bliss.

If you make a regular habit of feeding the local birds they will repay you by sitting in your trees and shrubs and shitting up a storm. This is another method of adding fertility to your land. Your own poo is valuable as well, but requires thoughtful handling to prevent disease. There is ample information online about how if you are inclined to recycle your own waste more fully.

Seaweed – This plant is an essential source of micronutrients, and will provide iodine, zinc and selenium among many other essential elements commonly lacking in New Zealand soils. Next time you are coastward bound, make sure you have a sack handy. Fill it up and take it home to compost and spread about under trees and shrubs.

Fish Waste – Liquid fish emulsions are commercially available but are often made from harvested wild fish, adding to the pressure on this dwindling resource. Better to find a source of local recyclable waste – fishing friends, restaurants and seafood suppliers. Fish heads, scales and bones are just about the richest source of nutrient available. Best to bury this waste directly into the garden as it can stink it up and attract unwanted pests. Plant on top of it and be amazed.

Sawdust – Make sure the wood source is untreated, as often timber is treated with chemicals to prevent rotting. Wood is hard organic matter and takes a long time to break down, requiring lots of nitrogen to make the process happen. The benefit is that this process soaks up excess soil nitrogen that might otherwise be lost by leaching. As the wood breaks down, stored nutrients become available again for the plants. Sawdust also to gives the soil good structure (friable and loamy), one that allows the easy passage of air and water and makes a great home for plant roots.

Mulch – Leaves and twigs and branches. If you don’t possess mulching machinery, simply bury the material in the ground. Leaves can also be spread directly onto the soil and covered with something heavier to hold them in place. Coffee grounds and lawn clippings are ideally suited to the task. Smaller twigs and leaves can easily be chopped up by a standard lawnmower, providing an easier product to deal with. In the New Zealand setting you will often find cabbage tree leaves. These highly fibrous leaves break down slowly but are an excellent addition to your soil. One method is to chop them down into little pieces that can be placed directly onto the soil or added to the mulch you have placed around fruiting trees and plants. Hedge clippers do the job just fine.

Cardboard – This processed wood pulp breaks down readily in soil and compost bins. It is also a fine way of starting off a raised bed. Simply lay it out on top of existing soil and cover with lawn clippings, coffee ground, poo and leaves. The cardboard provides a decent barrier between the existing soil – and all the weed seeds and other contaminants contained therein – and will eventually turn into soil itself. It is a food especially treasured by Tiger Worms.

Urine – Okay, it is not organic matter, but it is conducive to the processes that breaks down organic matter, so don’t flush it way, make use of it. This sterile waste is a brilliant source of nutrients – especially nitrogen – one of the most valuable plant nutrients and a key element in the decompositional method and any plant you apply it to will thrive (especially citrus).

Pee into a bucket and dilute with water (one measure of water to one measure of urine – careful, urine is potent stuff and can kill plants in a pure form) and apply around the base of fruit and ornamental trees or add directly to compost and even the soil between harvests (sparingly). You can also use this mix on your lawn. Simply throw the diluted mix directly from the bucket across the lawn and watch that grass become thick and lush. The increased yield of lawn clippings will also benefit your growing system.

In the end it’s a matter of imagination. Anything that was once living or comes from a living creature will make soil and all you have to do is keep your eyes open for sources. Remember that one person’s waste/rubbish is a gardener’s gold. Soil rich in organic matter is a nutrient generator. All the material you have added will eventually break down, releasing the component nutrients to the crop roots and the end result of all this activity is robust nutrient cycling. Seldom will you ever have to add nutrients from a bag, especially if you grow cover crops, which are grown specifically to enrich the soil.


A cover crop



Cover Crops

Legumes – Most commonly Lupins. Legumes (peas, clover, beans) have a special quality rare in plants: they can take nitrogen from the atmosphere and add it to the soil where it will become available for other plants.

Mustard – A rich fibrous plant like the Lupin that adds to the bulk of the soil (with soil as in people, fibre aids digestion), mustard also possesses chemical compounds that are not so good for less desirable soil organisms, famously the pesky Carrot Worm. Plant your carrots after your crop of mustard and say goodbye to Carrot Worm damage.

Wheat, Barley, Oats and Rye – These fibrous grasses are ideal soil building materials and grow well, like mustard and legumes, through the winter months (in New Zealand) when nothing much else does. Once they are a foot and a half into the sky they are ready to added back into the soil where they will decompose and feed the next food crop.

The general method is to dig these plants into the soil before they reach maturity but I am cautious about digging, understanding that it is a violent process that can disrupt well established communities of beneficial soil micro-flora and fauna. (You can successfully maintain a garden for decades without digging. Some traditional methods are just habits, so remember to examine your actions and study them before committing yourself to one way or another).

Often I simply chop the crop down and let it rot on the soil surface, to be later pulled under by earthworms. Cereal plants are more problematic, as they regrow. One solution is to pull them up, shake the soil loose from their roots and lay them back down on the ground. This process of preventing regrowth can be aided by adding a layer of something dense on top like lawn clippings. This will cut out the light and suffocate the plants in question.


Raised bed with pallet

How To Make A Raised Bed

When establishing a vegetable garden you can simply dig into the existing soil and start from there, but if you are on an older established section and have no knowledge of past usage, caution is advised. There may be lead paint contamination (especially so if your house is old) and a previous owner might have burned trash in a backyard incinerator, contaminating the immediate area. (Plastic burning releases serious toxins like Dioxin and Furan, which are among the most poisonous compounds). There may also be an issue with old garden practices and long banned chemicals that might still be present in the soil.

A raised bed properly made will prevent contaminants from entering into your food. Often raised beds are made from timber treated with chemicals that prevent rotting. There is evidence to suggest that these toxic chemicals can leach over time into your food soil and should perhaps be avoided. An alternative solution is to use pallet wood. Pallets are mostly discarded after one use and the timber is mostly untreated because this product is designed for disposability. They are free to pick up and easily disassembled. Sure, the wood will rot but not in any great hurry and if after a few years the timber is falling apart and is no longer suitable, simply replace.

Once you have your frame constructed and fastened to the ground, layer the existing soil with several sheets of box cardboard (after removing any non-biodegradable plastic tape and sellotape, and do not use heavily printed and laminated cardboard as both are polluting). Once you have a decent cardboard barrier on top of the old soil (it will also suppress the old lawn and seeds present in the ground) simply cover it with any of the organic material described earlier.

You are basically creating a compost heap, and for it to work properly it needs air circulation so make sure that you add woody material like twigs, mulch and sawdust between the lawn clippings, kitchen waste, poo and coffee grounds. Once you have a foot or two of material in place, cover it and let nature work its magic for a few months. I often cover with cardboard and lawn clippings (to hold the cardboard down and help it to rot) and hemp sacking which is readily available from any coffee roaster – it’s what the beans come in. This final layer will soak up unpleasant odours and make it nice and dark, a condition preferred by earthworms and many of the other creatures involved in the decomposition process.

And don’t forget to add a little lime and phosphate rock.


Raw Phosphate rock

The Raw Ingredients Of The Earth

In order to flourish living things need certain chemical elements, and the most important of these are nitrogen, phosphate, potassium, sulphur, calcium and magnesium. They can be found in the organic matter we are applying to the garden, but often this is not enough, at least at first when you are establishing the foundations of your new soil, and some supplementary sources are recommended, of which perhaps most important is Limestone – better known as nature’s soil sweetener.

Limestone is what happens when the shells of dead molluscs fall to the seafloor and pile up on top of each other over millions of years. Add some pressure and more time and the result is limestone, an unsurpassed source of calcium – the main component of all those shells. Finely ground limestone not only offers the gardener a ready source of calcium but it also adds a nice neutral temperature to the soil, one that most plants prefer – one that is neither too acid or alkaline.

Small quantities in regular cycles between harvests are best with some discretion, depending on a plant’s requirements. Potatoes for example, like their soil a little on the acidic side (as do many member of this family including peppers, eggplant and tomatoes) while member of the cabbage family prefer a well-limed soil. Limestone and its cousin Dolomite also help soil to maintain a nice friable consistency, which is the ideal for garden soil.

Dolomite Lime is similar to limestone except that this rock contains equal quantities of calcium and magnesium. It is a little more expensive but well worth the cost.

Phosphate Rock is the agricultural industry’s main source of an utterly essential element called phosphate. The rock is a product of volcanic activity and is usually treated with sulphuric acid to make the mineral content more readily available to the plants (this is called Superphosphate). The raw rock can also be applied, but be aware that the nutrients contained within become available slowly over time as weather and the activity of the soil wildlife break it down. In some ways the finely ground rock is better for the garden, providing a long-term source of valuable minerals that include a number of important trace elements – raw rock phosphate is also preferred by those wanting to create and maintain ‘natural’ organic style garden system. I prefer the raw rock myself because it ensures a robust long-term fertility.

There are numerous other finely ground mineral products available for the gardener, all of which offer the nutrients that are often lacking in New Zealand’s poor quality soils. This land mass is geographically young and the soils have not had much time to develop, and while the conditions are fertile, the soil is not. We lack phosphate, potassium, sulphur, calcium, magnesium, cobalt, selenium, zinc and iodine (and that’s just the short list). Mineral rocks can help address this lack and beside Phosphate Rock and Limestone, Granite Dust and finely ground shells (mussel and oyster dust is decent and cheap) are recommended. There are myriad other substances available: check online. Rocks and shells are a reliable storehouse of hard to obtain nutrients, and their addition to your land will make it stronger and more dynamic.


Potassium is another essential element to both plants and people. It’s a little more difficult to obtain, especially if you are not producing wood ash. Here I recommend the cautious addition of Muriate Potash (a natural element mined from the earth) from time to time, but if you are adding lots of organic matter to the system it’s a problem that will resolve itself. If you do not wish to directly fertilise your garden with elements from a bag, apply them to your lawn and wider property and then cycle it into the garden through composting.

Sulphur can also be a little hard to obtain. Once again, buy it in bagged form and distribute about your property for long time fertility gains. Eventually your system will be self-sustaining and with a dose of seaweed (a nutrient powerhouse) every now and again you should have no deficiency problems.



In the end, the purpose of creating decent soil is to ensure that the food you grow is of good quality – nutrient dense and tasty. It does not have cost a lot and the results are very satisfying. Soil making is not just a method for creating fertility – it is also an object lesson in recycling and living in harmony with the processes inherent in nature. Soil making is a deeply satisfying activity and soil itself is a beautiful thing to be nurtured and treasured.

As for chemicals, they have a place if used with caution and care. Organics is a traditional and well-proven method for creating and maintaining soil, but do not overlook the benefits modern science can offer the gardener. A little glyphosate (Roundup) can do wonders where an especially invasive and persistent weed is involved, and with this in mind I consider myself a pragmatic soil guardian with ecological tendencies rather than a hard-core organic gardener. Besides, a good quality soil means healthy plants and seldom in some 40 years of gardening have I ever had a real disease problem, just little seasonal niggles that one must accept as part and parcel of the gardener’s life. There is nice little rule that I hold dear: ‘Plant for yourself plus extra for the birds and insects and that way you will always have enough’.

Gardening is a creative act that benefits from a curious and active imagination. It is akin to composing music and applying paint to canvas. It is sculpture, writing, philosophical enquiry and engineering all rolled into one sweeping act of creative joy and like any creative pastime it requires the practitioner to cultivate skills and thoughtful practical wisdom. It is instinct, art and leisure. It is also meditation and spiritual supplication and finally it is an intimate connection with that vast force we call nature. The science suggests that gardeners live longer. It seems connection with the soil can be conducive to a healthy body and mind.



Some recommended reading to inspire and teach:

The One Straw Revolution by Masanobu Fukuota. Philosopher/farmer Fukuota explains his technique of ‘Do nothing farming’. A wonderful book about soil and plant cultivation as art.


Soil Grass and Cancer by Andre Voisin. French biochemist Voisin explores the relationship between soil and health.


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