The 1st Vital Key:

A Firm Foundation - Soil Basics

Virtually any subject one undertakes to master must be approached from the best possible perspective. Who would think, for example, to begin a study of medicine by writing a doctoral thesis or thrusting a scalpel into an abdomen? Would not a student first examine motives, follow with a definite plan, establish a set of goals, and finally launch a precisely-detailed, multi-year academic search into the human body, its systems and functions, human nutrition and healing processes? Even then, several intensive years of practice and hands-on experience would be required to finally achieve expert status...to be a successful, effective—and respected—physician.

What first-year student of law would consider marching boldly into court to defend world-class criminals before completing a thorough study of criminal law? Would she not first devote full energy and the necessary years to the process of learning the myriad nuances of law and courtroom procedure and politics?

Neither the unschooled physician-to-be nor the untrained and inexperienced aspiring attorney stands much more than a gasp of a chance of real, lasting success without first building a firm and secure foundation of knowledge. So it is with the student in the study of gardening. It seems only reasonable to begin a quest for the perfect garden by setting all else aside for the moment, and delving headlong into a subject as basic as soils...the very foundation of nearly everything having to do with gardening.

Almost literally, almost everything depends on healthy and alive soil! Because I feel so strongly that a thorough understanding of this foundational principle is essential, I'll spend ample time and space in this and other closely related chapters to make certain that the keys dealing with soil, once inserted into the lock, will function according to plan. So let's strip away all the too-technical outer layers and get right to the very core of the matter and, from the start, build our garden's strong and durable—and productive—soil foundation.

Picture in your mind the immense, sterile and probably very hot orbiting mass of rock and minerals that made up our earth shortly after its physical formation a few billion years ago.

Volcanoes flung massive rocks and debris mixed with choking smoke and hot gasses into the heavens from whence they returned to earth with a thundering crescendo. Boulders cracked and fell apart as they were cooled by rain and pounding waves. Moisture soaked deep into rock crevices, then froze. Expanding ice forced chunks and slices to split away, further reducing their size. Torrents of water rushing between fractured pieces of stone stirred them into a seething, crashing, giant cauldron of shattering rocks. Pieces of stone grew smaller and smaller as the incessant action of sun's rays, glaciers, winds of storm and the pounding rain of gigantic hurricanes and tornadoes gradually reduced once-huge boulders into pebbles and tiny grains of sand.

Add the ash and chemicals released by countless fuming volcanoes, and the still-mysterious sudden appearance of life, and after thousands times thousands of millennia of decaying plants and fallen animal life we have an active, though dangerously thin, residue we know as soil.

When you get right down to the nitty-gritty, soil is little more than a collection of tiny rock fragments, a little water, some air, minerals and decayed plants and animals. Reach down, scoop up a handful of the stuff and allow your imagination to soar. A close look reveals surprising lessons in chemistry and geology, biology and even history.

Blended with tiny grains of sand - fragments of once-huge boulders - are a wide array of complex ingredients. There are the remains of dinosaurs and giant pre-historic birds. Decayed corpses of giant trees, once lush and green. Frogs and bugs, men and women of ages long past, and all their wastes and garbage, now reduced to molecule-size specks of natural history. And tiny bits of precious metals and gems; once beautiful mansions and tiny cottages; stone-age tools and wood chips from a pioneer's adz; an old wooden toy lost perhaps centuries ago by one of your ancestors; and maybe the ashes of some long-forgotten funeral pyre.

There's an arrowhead and musket ball; a nail from the boot of an early settler and rotted slivers of railroad ties; the charred remains of clapboards and shingles which may have graced the home of a departed poet; love letters and priceless manuscripts reduced, by time and the elements, to dust, never to be read again! Flecks of paint, a clay marble and bits of iron from an old skillet. A powdery "soup" of sand, chemicals, minerals and organic matter slowly building itself, layer upon layer, into the very basis of human survival.

That's not all! Our handful of soil is so marvelously alive with countless tiny life forms, little wonder it doesn't writhe and pulsate as we hold it! The tiniest life cannot be seen but with a powerful microscope, yet they are, none the less, crucial to the health and structure of soil. They are the minute creatures and plant forms, the most important of which we call bacteria and fungi.

BACTERIA: Unbelievable as it must surely sound, there can be as many as one billion bacteria in a single gram of healthy soil. An acre of soil one foot thick can contain 1,000 pounds of bacteria! Though fragile and subject to damage when active and growing, they are rugged little rascals while in their resting stage resisting heat, cold, flood and drought. Puts me in mind of much larger animals that hibernate or use some other form of temporary suspended animation when the going gets tough.

Aerobic bacteria, those that require oxygen to survive, play an active role in converting nitrogen into more readily available ammonia and nitrates. They are also responsible, in part, for the efficient breakdown of organic material in the compost pile using, in the process, nitrogen as their fuel (much more about nitrogen and other soil nutrients in Chapter Three). Certain types of bacteria are less helpful in the garden and cause several distressing plant diseases (you'll read more of that in Chapter Seven).

Anaerobic bacteria are those which can survive without oxygen. The foul odor arising from a closed plastic bag full of recently mowed grass clippings, for example, is produced by the action of anaerobic bacteria. Anaerobic bacterial action is sometimes deliberately employed in the composting process but results are slow and odors can be oppressive.

FUNGI: Most fungi are important in the decomposition of organic matter and are present in much smaller numbers in soil, about one million per gram. Yet, because of their size, they weigh significantly more than bacteria, as much as one ton per acre! Fungi are actually plants on a near-microscopic scale growing into tangled masses of thready mycelium. They require oxygen and are generally well behaved in healthy, cultivated soil. Other types of fungi, however, are highly undesirable in the garden, causing infections on plants including rusts and various molds and mildews.

Bacteria and fungi are far from alone in healthy earth. In almost any discussion of creatures that inhabit the soil, EARTHWORMS are sure to come immediately to mind. They are the only insects which have no eyes, head, teeth, antennae or legs, the absence of which, though somewhat limiting, presents only minimal inconvenience. Oddly enough, one type of earthworm, the night crawler, instantly reacts to the white glow of a flashlight even though technically blind. They must have exquisitely fine tuned sensors of another type!

These wriggly and somewhat slippery little burrowers eat their way through the soil gulping down nearly everything in their paths which they sense is organic. Soil is taken in, passes through a digestive system not unlike a bird's gizzard, where ingredients which provide nourishment for the worm are extracted. Material that fails to satisfy its needs is expelled as "castings." This excrement quite often ends up on the surface and is normally higher in mineral content than the soil from whence it came. Since earthworms occupy depths ranging to several feet (depending on soil condition), this waste material serves the function of moving important nutrients around, making them more readily available to plants. Earthworms also aerate soils and their tunnels make it easier for water to penetrate rather than run off. Most gardeners are overjoyed to provide a suitable home for large colonies of earthworms and realize that these busy little subterranean cultivators should be preserved at all costs.

Practically every handful of soil in the world, with the possible exception of the permanently frozen northern- and southern-most sections, and hot, dry deserts, contains an abundance of another type of underground creature: NEMATODES. Sightless and "intellectually challenged" (they have no brain at all!), nematodes wander about looking for the nearest live root which they immediately attach themselves to and feed upon, frequently causing a small "knot" to form. Hence the name of a most troublesome type: root-knot nematode.

Nature usually does a decent job of controlling nematodes. The alternating heat and cold followed by drying out and saturation that occurs in most soils makes over-population an unlikelihood. Some types of fungi, constricting fungi, will actually attack, strangle and then consume nematodes. Bacteria, viruses, springtails, mites and a number of other soil-dwelling organisms also prey upon nematodes. On occasion, however, nematode populations get out of hand or one species or another will attack a particular type of plant. Sober thought must then be given to timely, if not drastic, control measures. In the event of a serious infestation, crop rotation discourages nematodes, as does thoroughly drying out the soil and exposing it to the bright, direct sunlight.

Certain types of nematodes can actually be helpful. A readily available nematode-based product attacks other pesky insects that spend at least some time during their development in the soil, cutworms and other insect larvae, for example. Additionally, there are even nematodes that prey mostly on other, more noxious nematodes.

Other Soil Life-Forms

In addition to bacteria, fungi, earthworms and nematodes, soil is home for a large and diverse group of life forms, chiefly insects. While a few live solely by predation or by consuming decaying plant material, the vast majority will at least occasionally feed upon, and therefore damage, living plant structures.

For now, it is enough to know that healthy soil is absolutely alive and crawling with a wondrous assortment of inhabitants, most of which are no real cause for concern. 

Just because you see a few "bugs" doesn't necessarily mean you have a problem serious enough to run for a bottle of insecticide. When one or the other proliferates and begins to damage or jeopardize a crop, however, that's the time to become concerned. Remember that in the average home garden or plant-crop-producing farm, a healthy, rich, well-drained soil with ample nutrition and moisture produces strong, healthy disease- and insect-resistant plants. Think of it: with healthy soil, and a fair amount of luck, you may never need insecticides again!

Soils, formed by the mechanical or chemical breakdown of rock, can become highly mobile. Rushing water carries away great quantities to be deposited far down-stream, where they become known as ALLUVIAL soils. Fine mud and clay, usually having poor drainage characteristics were it not for the addition of coarser grit and organic material, fall into this category. Fertile valleys between mountain ranges, the great Amazon Basin and the Mississippi Delta are examples. Such land is highly productive but in parts of the world, Bangladesh, for example, agricultural productivity is over-shadowed by loss of human and domestic animal life resulting from periodic flooding and storm. Undisturbed alluvial soils in profile reveal layer upon layer of different sized particles resulting from annual periodic flooding.

Wind is active in moving vast quantities of tiny specks of rock and organic material to be released downwind in concentrations reminiscent of sand dunes and snowdrifts. Accumulations of this type are referred to as LOESS (pronounced low-ess). Much of North and South America, and large areas of Europe and Asia, are made up of wind-blown sediments. History books tell of the disastrous dust storms of 1930s America and parts of Canada following several years of drought. When the storms had subsided, precious topsoil that once covered thousands of square miles of valuable farmland had all but disappeared.

Glaciers, too, pick up and move particles in astonishing quantities, leaving them hundreds, sometimes thousands of miles from where they began. Glacial soil is typically referred to as TILL and is usually well-drained, but nutrient-poor.

In a few places, notably the bogs of Canada and parts of the British Isles, soil is composed almost exclusively of built-up organic matter, generally (or until relatively recent times) covered with water. Soils formed in this manner have come to be known as RESIDUAL. Most gardeners are very familiar with material harvested from such areas. Peatmoss is its name and, when incorporated into the home garden, improving soil structure is said to be its game.

More than a few believe that recent periods of unfavorable harvesting weather, combined with what appears to be a certain desire on the part of peatmoss harvesters and packagers to increase profits, have led to occasional shortages at the retail level and some rather distressing adjustments in prices.

Not surprisingly, wind, water and the influence of humans have combined forces for thousands of years to create soils made up of a mixture of all four. Who among us has not seen dump trucks carting topsoil from one place to another? What avid gardener has not purchased bag after bag of peatmoss, sand, compost, manure and a host of other ingredients to improve his or her garden soil? Surely, all have witnessed a cloud of dust or seen fast-flowing muddy water.

A handful of today's "average" garden soil is composed of tiny (and some not so tiny) grains of sand and clay, bits of history and varying percentages of organic matter mixed with an almost endless assortment of chemical elements and life forms, hopefully separated by some air space and moistened from the heavens.

Most soils exist in "layers" starting with the uppermost: a crust we call surface-soil or TOPSOIL. In some parts of the world, topsoil is several feet thick while in others, near large sections of the New England coast for example, this usable layer may reach a depth of only a few inches or less. It is in this layer where most of the organic matter is found. Five percent organic matter is common though that may be slightly higher in seldom-cultivated soils and markedly lower in heavily used land. Generally, the more organic matter a soil contains the more moisture and nutrients it is able to retain and, therefore, the more life it is able to support.

Topsoil is usually the coarsest layer and is most commonly comprised of about half solids and half air space. Soils lacking in adequate air are unhealthy soils. Clay soils have less air space; sandy or gravelly soils allow more room for air. Since water displaces air, when it rains or floods, air is forced out. Very few garden plants or field crops thrive in saturated soil, so another very important characteristic of a healthy soil is drainage. Water tends to move in a downward direction, down hill. Very simply put: a healthy soil, composed of a mix of different-size particles and ample organic matter, accepts and retains the water it can use and allows excess to drain away. (More on drainage in a later paragraph.)

Directly beneath the surface-soil layer in most gardens lies the sub-surface soil which, if it were deeply cultivated, would normally be considered topsoil. However, most gardeners rarely, if ever, do more than scratch around the surface three or four inches.

Now comes primary soil layer number two: SUBSOIL. Here, the structure is much finer, often mineral-bearing clay. When water reaches the subsoil it usually slows down a great deal. Soil color changes, too, as the percentage of organic matter approaches zero. Subsoils are, however, a very necessary reservoir for nutritional elements, mostly mineral, which nearly all plants require to remain healthy. This quite necessary layer in garden soils serves to anchor plants, provide a storehouse of available nutrients and act as a reservoir to water the vast assortment of plant forms that we—or Nature—choose to place in it.

Normally, either solid or fractured rock lies directly beneath subsoil. I've heard this almost impermeable layer called "hard-pan," "bedrock" and more correctly (at least in my garden) "ledge." Practically nothing gets through this layer, with the possible exception of nitrogen in solution.

Observing the color of a sample of soil can reveal a great deal about its health and organic matter content. In real life, darker soils - brown to black - contain higher percentages of organic matter. In very warm and tropical areas, however, dark soils can contain as little as 3% organic material. So, as you can see, the rule has not been cast in bronze. Conversely, a soil that is light in color - light brown to tan - usually contains very little organic matter.

In most temperate areas, deep, very dark, loose, humusy and well-drained soil is almost always accompanied by healthy plants, ample flowers and generous harvests. Most slightly-better-than-average vegetable or flower gardens contain about 10% to 15% organic matter. More improved soils boast 25% to 30%.

A dead-giveaway of a "chemical garden" - one which rarely, if ever receives compost, manure, cover crops or any other useful form of organic matter - is what I call a "step-down" garden. Step-down gardens are a light tan color, usually contain large numbers of surface stones and are always lower than the surrounding lawn, paths or weed patch. There is precious little life in the soil of a step-down garden. Such soils cry out for a good shot of organic matter like compost or aged animal manure! In my opinion, a step-up garden should be the goal of every person who makes a conscious commitment and decision to be a responsible steward of soils and plants.

Very few cultivated plants prosper in soils that have impaired Drainage. Drainage is divided into five distinct classifications. Well-drained soils allow roots to penetrate to a depth of about 36" without running into excess water. Moderately well drained soils, the type found in most improved and deeply cultivated gardens permit roots to reach 18" to 20" deep without being hampered by excess water. Roots in somewhat poorly drained soils rarely penetrate beyond 12" or 14" deep. Soils that remain wet most of the time are referred to as poorly-drained. Alders and willows are common in these conditions, as is the presence of some types of ferns, mosses and wetland wildflowers like purple loosestrife and jack-in-the-pulpit. Water stands on or near the surface nearly all year on very poorly drained soils. Pseudacorus iris (yellow flag) thrives in these conditions; very little else except weeds and some aquatic plants will even barely survive there.

A soil which is easily cultivated, one in which lumps readily fall apart when spaded, is referred to as having good tilth. The same term also applies to soils through which roots can easily penetrate, and which tiny seedlings can break through with ease.

One very important characteristic gardeners have considerable control over is soil temperature. Below 18" to 24" deep, temperature rarely changes, except in the far north where deep-winter frost penetrates to as much as 4 feet, or more! Within a few inches of the surface, however, temperatures change almost as much as ambient air temperature. As you might have guessed, dark, rich soil warms up faster in sunlight than does lighter, poorer types.

Germinating seeds are usually inhibited by cooler soils, whereas in warmer ones infant plants almost leap out of the ground. Mulches tend to moderate soil temperature, keeping it a little cooler during the worst heat of summer (also conserving moisture and hindering the growth of weeds), and preventing frost from penetrating quite as deep during the worst cold of winter. Soil temperature can be artificially raised in the spring through the use of dark-colored coverings like roofing paper, black landscape weed barrier or dark-colored polyethylene sheeting.

Frequent walking or driving heavy machinery, garden tractors, and loaded carts and wheelbarrows on garden soils can cause soil compaction. Structure and tilth are ruined; neither air nor water can be absorbed; and plant roots cannot penetrate. Compacted soils can be restored to health by deep aerating and cultivating, and by planting cover crops like annual clover or grasses which may be tilled-in later. My advice to you is to never tread on, or allow visitors or children to tread on, any garden soil, especially if it's just been cultivated or watered.

A Gnawing Problem

Alas, soil is now seeing itself wasted and impoverished at the hands of its greatest enemy: humankind. In our hunger for riches, our lust for pleasures and our characteristic striving for dominance, we blindly and tragically abuse the very resource that supports in one way or another every life form on the face of our troubled, exhausted and sometimes contaminated Earth.

Vast areas of our planet lie utterly useless mostly because of a stewardship philosophy of take all, get everything, but put little or nothing back. Some among us soothe their consciences and fatten their wallets by pouring on huge quantities of chemicals to make up for the exhausted natural nutrients and humus. The result: diminished food and forage production, and considerably reduced nutritional value. Tangled among the snarls of greed and waste are enlargement of wastelands and deserts, destruction of life forms vital to the proper function of our food chain, fouling of critical water supplies, and other crises, not the least of which is a stunning increase in chronic illness and debilitating disease.

A glaring and prime example of tragic loss of food-producing land is dramatized by chemical salt build-up in California's once-fertile San Fernando Valley. But the awful waste is certainly not limited to our American southwest. Starved for humus (organic matter normally found in healthy soil), and artificially fed and watered, thousands times thousands of acres of land the world over can almost be heard as they gasp their pitiful last breaths.

Sorry about getting a little ahead of myself here. What's important to remember at this point is that topsoil, no matter where or in what blessed or shameful condition of health, is a key link in our food chain, our life chain. Argue as some do, there is no escaping the appalling fact that if our soil goes, we go! If and when that happens, rest assured, it won't be pleasant. Truth be known, much of our once-productive land is either gone, or is well on its way to literal oblivion, unless something is done about it, soon.

The stinging conclusion is inescapable: We all have an obligation to protect every remaining ounce of soil and scrap of compostable organic matter. Just as it is our right and privilege to be a part of and partake of the resources provided for us, it is our responsibility, right and privilege to preserve, indeed, improve and restore, that which our children and all succeeding generations must rely upon for their very existence. More's to follow relating to these and other pressing responsibilities in later chapters.

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There you have it, a quick and very basic course in soils. An exposition on the subject could get a great deal more complicated but enough is given here to lay the groundwork for what's to come. From this point on I'll assume that you are striving to become a responsible gardener and have at very least average garden soil capable of supporting plant life. I'll also assume that your "average" soil needs some help in the way of amendments or other improvements. Your job will be to find out exactly what your particular plot has in the way of essential nutrients, minerals and humus; whether it's acidic or alkaline; and what type of soil you have to work with. To help you do that....

Proceed to Key Number 2:Testing Your Foundation