The Real Dirt
I was an organic gardener long before I knew what the term meant. When I started gardening decades ago, labels on fertilizer packages with 10–10–10 or 2–10–whatever baffled me. These products all seemed to be manufactured by the same big chemical companies that I was, no doubt, boycotting because of their involvement in the Vietnam War. Since I was composting out of habit and the garden seemed healthy enough, I didn’t bother with synthetic fertilizers. Through laziness I was doing exactly what I should have been doing— ecological gardening by default.
The most important philosophical gardening question to ask yourself is this: What is the nature of soil? Think for a moment about how we even acquired this miraculous substance. Over millions of years, massive upheavals around the world exposed huge rocks, then glacial movements scoured them clean. In the retreat of the great ice sheets, moraines, boulders and clay were left behind. They became deposits of gravel and sand as they were pounded away by wind and rain. Over the eons, through the action of bacteria, fungi, lichens, insects and eventually earthworms, thin layers of soil emerged.
In fact, the earth you stand on in your garden seethes with life. Imagine big animals devouring little animals, think of ancient migrations and the drama of birth and death all going on in a dark world that requires oxygen and water to survive. Sounds a lot like what happens on top of the soil, doesn’t it? Though we are very concerned about the quality of our air, we seldom think about this other part of the biosphere.
Half the soil consists of solid material, mostly mineral particles, and half consists of the spaces between this material; and half of these, in turn, are filled with water that occurs as a film around the particles. All these microscopic bits and pieces are so vital that without them we would be doomed.
What’s taking place in this subterranean world is a cycle of death and decomposition, as one kind of organism becomes food for others. Eventually these death throes supply all the nutrients needed by plants. The ultimate in recycling. Every plant you add has a function within this community: some fix nitrogen in the soil, some are deep-rooted, diving downwards for water, while others with shallow roots take advantage of limited rain.
The most devastating part of all this is that we are ill-informed about these relationships and even the cleverest of scientists doesn’t know the whole story. Most of us seldom think about soil at all. Life is churning away beneath our feet and yet every move we make serves to kill it off. Our prairies once had the most fertile soil in the world, an extraordinary humus created over thousands of years. We’ve managed to deplete it in a century with one-crop farming (monoculture), ripping out the native grasses (polyculture) that held it in place, leaving it exposed to the elements, and allowing humongous machinery to drive over and compact it. All this activity conspires to destroy the life below the surface. Add the assault of chemical fertilizers almost non-stop for forty years, plus pollution, fires and floods and you’ll begin to understand what’s happening to this fragile ecosystem.
The microscopic animals of the soil live a full life if they are allowed to. They browse, swim, travel, have profligate sex lives, procreate and die, providing food for the big guys— arthropods and earthworms. The symbiosis among these animals is highly structured. What happens when we interfere chemically with all this activity is that we slowly poison the soil by killing off mites, bacteria, fungi and, even worse, earthworms. The remaining species multiply. This throws off the balance entirely as the level of chemicals steadily increases until the soil becomes toxic to plants, animals and people.
What keeps the soil healthy are all these organisms in the perpetual process of decomposition. Dying matter breaks down into humus and, through this, releases nutrients for plants. When we put the soil in jeopardy, our very survival is in question.
Dr. Stuart B. Hill, professor of entimology and soil guru, says that rather than killing off bacteria and fungi, we should be investigating and developing management strategies for their productive potential.
“Such strategies,” he maintains, “are likely to save money, energy, and avoid damage to the support environment and to human and livestock health. This contrasts with our current approach, which involves the removal of several dozen minerals at harvest time followed by the replacement of only a few of them as chemical fertilizers” (Agricultural Chemicals and the Soil [1977]).
Bioagriculturists consider pests and diseases to be symptoms of poor soil management. Pesticides, antibiotics and drugs have generally been regarded as “magic bullets” that can eliminate problems. “The real situation,” Dr. Hill says, “is that we do not suffer from pests because of a deficiency of pesticide in the environment just as we do not get a headache because of a deficiency of aspirin in the blood.” Keep that line in mind when you get into an argument with a chemical pusher.
This dependency on chemicals is much like an addiction. The more you use, the more you need merely to survive. But the depletion of soil expands exponentially, and what little short-term gain there is for the private person will eventually become a huge costly public burden as we all try to recover the health of our soil.
The soil has amazing strategies of its own for dealing with harmful things. For instance, there are nematodes that are dreadful killers. They get into the roots of plants and suck them dry. To counter this, there are fungi that strangle the bad nematodes. Most other nematodes are helpful to the soil; some kill off plant pests.
To give you an idea of just how complex all of this is, consider that there may be a hundred thousand protozoa in the water that surrounds a few particles of soil. The millions of bacteria in each gram of soil are crucial to decomposition. To aid the process, there’s the activity of earthworms.
Aristotle referred to earthworms as the intestines of the earth and Darwin called them nature’s ploughmen. Earthworms, Darwin calculated, could move 7.5 to 18 tonnes of soil per acre (0.4 ha) annually.
North American earthworms are thought to have been pretty much done in by the last ice age. One of the things Europeans did when they came to this continent was to bring earthworms with them. There are now twenty-three recorded species in Canada, including a couple of native ones. Earthworms eat up fallen leaves and start the whole decomposition process, though they won’t work on fresh beech or oak leaves with the same efficiency as on other leaves. They gobble up organic matter and leave behind castings filled with calcium, potassium and phosphorus; they stir up the soil and bring nutritional material closer to the surface and more accessible to plants; and they aerate the soil through burrows that bring oxygen to the bacteria that need it to survive. Their burrows also provide channels for roots and increase the ability of water to move through the soil.
Worms aid in creating the all-important humus. They hate anything that messes with soil life—especially synthetic fertilizers. So we should be aware of worms’ value. In each square yard (metre) of healthy soil, there will be about 300 earthworms. In anything but really acidic soil, if you haven’t got a lot of wormy activity, you’ve got a problem.
No doubt there is a platonic form that contains the perfect soil: dark loam containing enough balanced humus to hold just the right amount of rain but with excellent drainage. It’s out there somewhere, but the soil most of us are usually presented with has something wrong with it: too heavy, too sandy, too much clay and always, always, the possibility of past over-cultivation. This can happen in a few seasons if nothing organic is put back into the soil. What your soil probably needs is some form of conditioning.
Fertile soil is the result of a cumulative process of continuous improvement. Two things are required: humus and finely ground rock particles. The latter make up the mineral portion of the soil. But it is the humus or organic matter that is most important. Dr. Hill refers to the humus-creation process as a primitive form of farming that’s been going on for 400 million years. What keeps the farm thriving is the decomposition of organic matter.
Organic matter is comprised of living matter, such as leaves, in the process of decay. To break down, leaves need many different fungi, each with a special function, to attack them. Then there are mites and other arthropods that come next. If you destroy any of these with pesticides, you can upset the balance needed for proper decomposition. Since most of these creatures are beneficial, it seems unnecessary to go on a chemical rampage for the few that might be malevolent. You might also destroy their natural predators, thus reducing any short-term good that the chemicals might provide.
Some organisms, such as mycorrhizal fungi, perform Herculean tasks in the soil. They not only improve plant health, they also help plants absorb phosphorus, so essential to growth, and assimilate trace elements, which assist plants in withstanding the stress of drought. Experiments in how to use these fungi as an inoculum are now under way. And what do they need in order to prosper? Aerated soil with lots of organic matter. But they won’t co-operate if pesticides and herbicides have been used.
The more intimate you are with your soil, the better handle you’ll have on dealing with any problems that arise. To feed the soil, you need to know what the menu should be.
THE STRUCTURE OF SOIL Soil comes in layers. Depending on how great your soil is, each layer will be from a few inches (centimetres) to a few feet (metres) thick. Arising from the bedrock of the earth, soil is like a thin skin on its surface. It takes about 500 years to create 1 inch (2.5 centimetres) of soil through weathering.
The texture of soil depends on the sand, clay and silt content. The ideal loam is 25 percent water and 25 percent air, with the balance made up of organic matter—all the animals and tiny organisms that live there plus minerals. In this same ideal soil, micro-organisms release 3 pounds (1.3 kilograms) of nitrogen a year, which is about the equivalent of a 50-pound (23-kilogram) bag of 6–10–4 commercial fertilizer. All of the nitrogen and sulphur, and one-third of the phosphorus and other nutrients are supplied by organic matter.
Humus: The top layer of organic matter, decayed and in the process of decaying, is humus. It helps the soil absorb water, provides air spaces critical to plant development and is filled with the nutrients plants need for survival.
Topsoil: This is where the life of your soil is found. Earthworms, bacteria and a multitude of other animal organisms live here. It contains minerals and organic matter ranging from 49 percent to 1 percent, depending on the location. The depth could be from a fraction of an inch (a few millimetres) to 18 inches (45 centimetres) or more.
Subsoil: There are fewer nutrients at this level. The material here is pulverized and there’s no humus. But soil conditioning can help improve a shallow subsoil.
Hardpan: This is self-descriptive. Clay and silt make it almost impermeable. At this level there is little or no drainage. The closer to the surface you find hardpan, the more shallow-rooted the plants will be.
Bedrock: There is no soil below this level.
TYPES OF SOIL To evaluate your soil, dig out a chunk of earth approximately 12 inches (30 centimetres) deep. Now pull a fistful from the centre of the batch. Moisten it slightly and then squeeze it in your hand to figure out what type of soil you have.
Heavy: If the moistened soil holds the shape of your hand, you’ve got heavy—or clay—soil. Clay has very few spaces between the tiny particles. That means it has poor drainage and is slow to warm up in the spring. It needs to be lightened up with organic matter, such as humus or compost, plus sand, for improved drainage.
Perfect: The best soil, loam, is 40 percent sand, 40 percent silt, 20 percent clay. It’s great stuff, perfectly balanced. When you squeeze it, it makes a ball that falls apart easily. It drains readily, which is what, ideally, you are aiming for. Once you have loam, keep adding compost or humus to keep it up to scratch.
Light: Mainly sandy, light soil won’t hold together in your fist. It’s very gritty stuff with large particles that let water drain away far too quickly. This kind of soil needs an underlying level of humus or organic matter such as well-rotted leaves.
Mixed: Silty loam feels smooth and holds its shape. Sandy loam is gritty and forms a ball. If you have a soggy mess of mucky peat soil that just sort of plops in the hand, it needs serious amending.
SOIL TESTING If you’re unsure whether you have acid or alkaline soil, have it tested at a garden centre, agricultural station or soil laboratory. There are also kits available that are relatively efficient.
To prepare a soil test, dig a sample from every 100 square feet (9 square metres) to a depth of 6 to 12 inches (15 to 30 centimetres). Mix the sample in a bucket and send about a pint (1/2 litre) of this mix to be tested. If you describe what you want to plant, the soil can be tested for that purpose. You will be given the nutrient content, pH and a description of texture. On the pH scale of 0 to 14, acid soil is below 7, neutral soil is 7, and alkaline soil is above 7. Most plants—and soil organisms—like a pH between 6.5 and 7.
ACID SOIL—BELOW 7.0 pH A fast way to figure out if you have acid soil is to take a small amount and add a bit of vinegar. If the vinegar sizzles, you’ve got alkaline soil. If not, that means there’s acid in it and the vinegar (itself an acid) won’t react with it. Weeds will also let you know if you have acid soil: meadow foxtails, daisies, mouse-ear hawkweed, corn marigold or corn chrysanthemum, corn spurry, sheep sorrel, sow thistle, coltsfoot, nettles and masses of Johnny-jump-ups all indicate acid soil.
FOR PLANTS NEEDING ACID SOIL If you don’t have acid soil but want to grow acid-loving plants such as rhododendrons, azaleas and heaths, which like a pH of 4.5 to 6.0, try the following:
Dig out a bed 18 inches (45 centimetres) deep and fill with a mixture of sharp sand and garden loam to 3 parts coir, or sawdust from pines or oak. Add 5 pounds (2 kilograms) of sulphur per 100 square feet (9 square metres).
Once the acid-loving plant is in place, add 2 teaspoons (10 grams) of powdered sulphur every square foot (.09 square metre).
To acidify the soil in a small area, you can also try adding vinegar and coffee grounds a little bit at a time.
Don’t use peat moss. Though over time it will acidify the soil, it’s a non-renewable resource and is sterile. If you insist on peat moss, soak it with hot water and let it sit; this will help it to add moisture-retention qualities to the soil. Dig it in and allow the bed to winter over before planting.
Don’t use bone meal or wood ashes—both contain lime and will reduce the acidity of the soil.
Check out the rainwater. In many cities, rain is becoming increasingly acidic due to pollution. Collect rainwater in drums and use it to water acid-loving plants.
Mulch with leaf mould from oaks and pines.
Lime will reduce acidity. Dolomitic limestone contains magnesium and calcium, thus fertilizing the soil at the same time. It is the recommended form. Apply in the fall after the ground is dug or ploughed, to give it a chance to break down—which it does very slowly.
Wood ashes are about 20 to 50 percent calcium carbonate and thus will act quickly to reduce acidity. They are high in phosphorus. The best time to apply is late winter or early spring, but never apply them near germinating seeds.
NEUTRAL SOIL—7.0 pH Most plants like to grow in slightly acid to neutral soil (6.5 to 7 pH), which can be maintained with proper mulching and fertilizing (see chapter 3).
ALKALINE SOIL—ABOVE 7.0 pH Some soils are too alkaline for plants. Weeds indicating alkalinity include white mustard, clustered bellflower, musk thistle, black knapweed, Queen-Anne’s lace, salad burnet and henbane.
If soil is too alkaline, try the following:
Add sulphur to lower the pH if it’s too high for what you want to plant.
Try adding other materials that will lower the pH, such as calcium sulphate and aluminum sulphate.
Add compost, about 2 to 3 inches (5 to 7.5 centimetres) a year, which will make soil more neutral.
WHAT’S IN SOIL The three major elements that plants require in large quantities of soil are nitrogen, phosphorus and potassium. These are the NPK numbers on fertilizer bags—if the number is 21–7–7, that means it contains 21 percent nitrogen, and 7 percent each of phosphorus and potassium. There are vital interrelations between all the elements in the soil. Once again, it’s your job to maintain the delicate balance.
The other major elements in the soil are carbon, hydrogen, oxygen, calcium, magnesium and iron. Then there are the trace elements: boron, copper, manganese, zinc, molybdenum, sulphur and zinc. These are the hardest to manipulate, so concentrate on the major elements.
Nitrogen is released when soil organisms decompose. When a plant dies, most of the nutrients taken out of the soil are returned to the soil. This in turn is transformed into humus, which contains the acids that make other nutrients available to plants. Nitrogen production increases under warm, moist conditions and slopes off under cool conditions. Nitrogen is needed for vegetative plant growth.
Organic matter in the soil is crucial for soil micro-organisms to release nitrogen. Leaf mould, compost, manure, dead roots and plants, insects and animals and the minutiae of the soil—including bacteria and fungi—are all organic matter. The ultimate goal of this decaying process is the production of humus—the most superb type of organic matter you can build for your soil. When you walk through the woods, lift some moss or rotting leaves. The marvellous sticky black stuff under them is humus. The process of decomposition has been completed and it is feeding the soil. This is the material that will heal your soil if it’s sick.
GREEN TIPS
SOURCES OF NITROGEN INCLUDE:
Fish emulsion.
Blood meal, which has a nitrogen content of 8 to 13 percent.
Sheep manure—if you use manure to bump up the nitrogen content of your soil, I recommend sheep manure, which has a higher nitrogen content than other types. Use manure that’s been composted for at least six months (the heating process will kill off any weed seeds). Manure will also improve soil texture.
Finished compost is an excellent source of nitrogen.
The beauty of these products is that they release nitrogen slowly and naturally—usually as the plants need it. They aren’t going to burn the plants or you.
On the other hand, synthetic forms of nitrogen have a much higher nitrogen content. Anhydrous ammonia is about 82 percent nitrogen. If you breathe it, you can die. If it gets too close to the root system of a plant, it causes damage. Urea has 45 percent nitrogen; if it’s mishandled, plants will die. Most chemical fertilizers with high nitrogen content are taken up so quickly by a plant’s root system that the plant produces initial lush growth, which is watery and weak, more susceptible to disease and easily broken off by the wind.
Phosphorus is needed for fruit development and root growth. It also helps plants resist disease and withstand the stress of drought and pollution. Mix any of the following sources of phosphorus with manure and dig in in the spring. This nutrient doesn’t leach out easily and is released into the soil slowly.
GREEN TIPS
SOURCES OF PHOSPHORUS INCLUDE:
Colloidal phosphate—18 to 25 percent phosphoric acid. Use every four years.
Rock phosphate and greensand have long been recommended, but if they come from North America they’ll contain uranium, which might contaminate the soil.
Bone meal.
Superphosphate is a rock phosphate processed with sulphuric acid. I try to keep away from products that require a lot of energy in their production. It also comes from great distances (Togo and Morocco). Find something else.
Rock and colloidal phosphate will raise the soil pH, making it less acid.
When you are using rock minerals, use them in a natural form. By doing this, you will avoid getting into the problem of excessive mineralization or the leaching of soluble elements, which could affect groundwater.
Potassium is needed for growth. It helps plants resist disease and protects them from cold and from excessive loss of water. Too much magnesium in the soil will lead to a potassium deficiency.
GREEN TIPS
SOURCES OF POTASSIUM INCLUDE:
Wood ashes (from the fireplace, not the barbecue), but be careful—they can boost the pH, and if it gets too high, you’ll kill off your acid-loving plants.
Manure—sheep and goat manure have the highest potassium content (3 percent).
Add straw.
Bananas; bury banana skins near rose bushes.
Micronutrients such as manganese, iodine, zinc, iron, copper, boron and molybdenum are all in the soil and if they aren’t, your plants will let you know that something is wrong. Lots of organic matter settled on top of the soil and allowed to work itself in slowly will correct any imbalances. It contains these trace elements and is the simplest, safest way to a healthy soil.
Balance is everything. When the temperature rises and the soil is moist, all these nutrients will become available to the plants much more quickly.
Create self-sufficient soil by making it healthy. You don’t want to provide temporary solutions to any problems. Manure and organic matter aren’t necessarily interchangeable in ecological gardening. Organic matter is the most important: leaves, plant waste, garden detritus, straw, hay. Straw, alas, encourages mice.
Another method of enriching the soil is to dig down and fill the hole with layers of aged leaves and manure. Earthworms do most of the work of breaking down these materials into compost.
Build up the soil with compost or make your own organic fertilizer as recommended by garden writer Eliot Coleman: 4 parts blood meal, 2 parts bone meal and 1 part kelp or rock phosphate.
Here’s a good soil food recommended in the book Organic Gardening for the Pacific Northwest: 4 parts seed meal (or 2 parts fish meal), 1 part dolomitic limestone, 1 part rock phosphate or 1/2 part bone meal, 1 part kelp.
If you add bone and blood meal to coir, it will act as a fertilizer. Coir products are made from coconut fibre (from outer husk) and are used as an alternative to peat moss. Though I realize coir products have to be shipped long distances, that’s better than destroying peat bogs.
Leaf mould is an excellent amendment. Bag leaves and place them in a corner to break down, or dig them into a big hole and let them rot, or shred them and add to the compost heap. One thing you don’t do with leaves is throw them out.
Maple leaves tend to mat if you put them on the ground without letting them break down first. Since the leaves of Norway maples contain alkaloids, they should be well composted before you add them to the soil. Oak and beech are acidic and will take longer to break down than other leaves. But they are great if you are building up acid areas in your garden. Black walnut leaves contain juglone, which is toxic to many plants, so you should probably not use these leaves as soil amenders.
Extremely sandy soil is too porous and it won’t support earthworms. Add masses of compost and keep adding as often as possible. Over time the soil will improve.
If you have soil with poor texture or density, try the following:
Double dig: Dig a trench as wide as your spade, and as deep. Pile the soil from this first trench on a sheet of plastic. Loosen and amend the soil in the bottom of the trench to another spade depth. Dig another trench directly beside the first trench and put the excavated soil in the first trench; continue until you hit the last trench and then put the soil on the plastic sheet from the first in it. In all my years of gardening I have never done this, but some people swear by it.
Raised beds: Double dig the soil and add enough moistened coir and compost or manure to raise the soil at least 8 to 10 inches (20 to 25 centimetres) above ground level. Always mix coir with other soil amenders; on its own it’s sterile.
LEAD IN THE SOIL: Though lead hasn’t been used in paint or gasoline for some time, there is still the possibility that it might have built up in the soil, especially if you live near a parking lot or busy road. By adding lots of compost and manure, you can decrease lead absorption. By maintaining neutral soil of pH 6.5 to 7, you’ll also be able to limit the build-up of lead in the soil.
ROCKY SOIL: If you have a lot of rocks on your property, you can use them in the garden. Position plants that like hot, dry conditions near large rocks. Place smooth, flat rocks near plants that like cool, moist conditions—put rocks over the roots of clematis, for instance.
If you must buy topsoil, be careful. Try to find out where it came from. If it’s from a field that was planted with corn, it may be filled with toxic chemicals. In that case, don’t buy it. Of course, it is likely to have come from the nearest housing development. The valuable topsoil is removed and sold, leaving new homeowners with nothing but subsoil and clay. If you’re in this situation, bump up the soil first before you go through the heartbreak of putting in a garden and watching it struggle. Use huge amounts of compost and manure to create healthy soil and keep it that way. Don’t be tempted by quick solutions.
Instead of buying soil, you can prepare your own potting soil mix—particularly if you have fears about vermiculite, which may contain asbestos, in commercial mixes. A combination of clean soil, sand (builder’s or horticultural sand is very gritty) and compost is a very good growing medium.
I don’t mess around with soil by cultivating it once it’s been planted. I like to think I’m not disturbing the complex life or delicate root systems that exist down there. After all, the most beneficial life in the soil is in the top inch (2.5 centimetres).
To create a healthy, balanced soil in your ecological garden, use every alternative to cultivating that you can find. Be sure to mulch and otherwise keep the soil covered. (If you want to see what will happen when you fail to protect the soil, take a chunk of bare earth and aim your hose at it.) Return what you take from the garden to the garden (leaves, dead and dying plants—unless they are diseased). Feed with organic matter. Compost, compost, compost.
GREEN TIPS
SOIL LESSONS:
Make sure you know what kind of soil and drainage you have, and work with it or amend it to accommodate the plants you want to grow. Find out what was added to your soil before you took possession. If the area has been stripped of topsoil or if chemicals have built up in the soil, you will have to improve the soil over a period of time.
Plant when pests are less evident.
A handy way to inoculate your soil against diseases is to plant marigolds, and then rotate them from year to year. An added bonus: rodents don’t like them.
Learn to treasure the soil and approach it as a living creature rather than some dead stuff you clunk plants into. The more you are aware of the symbiosis between yourself and the soil, the more careful you will be with this miraculous substance.
To find out where there are accredited soil testing labs in your area, Google “soil testing” plus your province or state, and you’ll get an up-to-date address. When sending soil off to the lab, be sure to ask for organic solutions to any problem they find.