Chapter 1. From the Ground Up - A General View of Soils

"The earth is the mother of us all - plants, animals and men. The phosphorus and calcium of the earth build our skeletons and nervous systems. Everything else our bodies need except air and sun comes from the earth."

Henry A. Wallace, in the Foreword to
"Soils and Men,"
the 1938 Yearbook of the United States
Department of Agriculture.

Without soils, no life could exist on earth. The lowly bacterial cell and the massive pachyderm both owe their being to this basic stuff of life. A bird in flight, a mole burrowing beneath your lawn, borers eating blindly into the heart of a great oak-all are linked by their common dependency on the elements of existence they draw from the soil.

Of all the earth's living creatures, man alone manipulates and modifies the land to better suit his ends. Not satisfied with soil as he finds it, he tears its surface, incorporates organic and mineral materials and alters age-old structures. He often keys his actions to two false but widely held ideas: 1, that soils are simply clay and decaying vegetable matter-a mechanical support for plants - and 2, that the easy-digging quality of the soil means more than its chemical-bio­logical quality. The error of this over-all viewpoint was thrown into sharp focus not so many years ago by the controversy concerning the use of synthetic chemical soil conditioners. These products often made soil easier to till but with no resulting improvement in quality of plant growth. The "organocultists," those who believe only in organic gardening, have much to say about all this. Their ideas are aired in a later chapter.

Tips on Types

Soil type is important. Type is determined largely by texture, a word often used in the wrong sense. It means simply particle size, such as fine sand, gravel, silt, clay, and so on.

Particle sizes in soils range something like this (mm = millimeter; 25 millimeters equal one inch):

Organic matter in soils may range in size from as large as entire plants that have been dug under to as small as humus particles so fine that they form colloidal solutions. (In a colloidal solution the minute particles do not settle out, but float indefinitely.)

Based on the preceding information, here is a soil classification according to particle size (comments are explained throughout the book):

Soil type has to do with mechanical makeup of soil. Type does not give much clue to the value of a given soil for growing plants. By habit we associate loams with rich soils, yet certain loams may be poorer than some clay or sandy soils.

Soil type concerns you in three vital ways. First, many recommendations for applying fertilizer, for treatments to adjust pH (acidity-alkalinity) , and for other applications of chemical substances to soil give different rates for clay, sand, and other types. Second, a knowledge of texture-types gives some clue as to how well a soil will hold fertility. (Fall feeding is possible for a lawn on clay loam soil, for example, where this would be unsuccessful on a light sandy loam.) Third, knowing your soil type will often tell you in advance whether it will drain well or will puddle and wash under heavy rains.

These three points are chiefly important now, at the beginning of our discussion on converting a native soil into Gardener's Loam. They will lose their importance once we have incorporated soil amendments and extra organic matter into the soil, for then original type will be so modified that it will have to be revaluated in light of its new characteristics.

An accurate test of texture and type requires an involved laboratory procedure. A rough check, accurate enough for gardening purposes, can be made by the soil wash test, as described in the chapter on testing (Chapter Three).

A Culture of Microorganisms

"I certainly don't want to add germs to my soil," exclaimed one gardener when I tried to persuade him to treat peas and beans with a nitrogen-bacteria culture. He would have been astounded if he could have seen the billions upon billions of microorganisms he harbored in his relatively poor soil. He just could not accept the idea that soil is a culture of such organisms, just as much as it is a me­chanical support for plant roots.

Few gardeners deliberately set out to increase the biological life of soil, yet this is the main purpose behind every addition of organic matter. (Long before he knew why, man observed that plants grew best around places where rotting plants and manure had accum­ulated.) When we treat soils so that beneficial bacteria and useful fungi are stimulated, plants grow better and returns for time, effort and money used are increased. Much of this benefit concerns plants that prefer near-alkaline soils. Acid-soil species, however, are also benefited by the stimulation of useful fungi. A good example of this are the mycorrhizae-specialized fungi that form a feltlike covering on roots of acid soil plants and help them use ammonia as a source of nitrogen. Without these fungi operating in the soil, rhododen­drons, azaleas, blueberries, hollies and many other ericaceous plants grow poorly, if at all. When we provide conditions that favor rapid increase and continued growth of mycorrhizae, these plants thrive. If, however, plants are set in heavy clay or planted so deeply that air does not move freely around the roots; or when soil moisture fluctuates widely (sometimes wet and sometimes dry), or when a protective mulch is missing, both plant and fungi suffer. I have several times made the statement, "To a considerable extent, the culture of acid-soil plants is the culture of mycorrhizae. Do what is good for the fungi and the plants will thrive." The same might be said for plants that thrive in less acid soils as well.

The function of fungi and bacteria is to process and make available food elements too complex for higher plants to absorb. This vital process will be explained later in detail.

Soil organisms are important in another way: as they live and die they absorb, conserve and then gradually release soluble nutrients that might otherwise be lost; thus they increase fertilizer utilization many times over.

Soil as a Chemical Laboratory

Although each phase of soil already mentioned is vital, we cannot lose sight of soil as a chemical-mineral material. We must also re­member that all nutrients are absorbed either as relatively simple chemical compounds or in nearly elemental form. Plants are unable to directly use complex proteins, animal wastes or similar products of growth. Decay must first release stored foods in simpler forms, then these are taken up by roots.

For this reason, we must study the chemical side of soils, to understand why conversion of organic matter to simpler products is a vital phase of soil. Chemical, as opposed to organic, fertilizers have become the subject of much controversy. Later on (in Chapter Five) we will explore the relative merits of these fertilizers.

All nutrients used by plants must be in liquid form, since plants have no teeth or specialized organs for grinding solid foods and lack any semblance of a digestive system. For this reason, water is an­other vital factor in assuring maximum growth in any soil. About 98 per cent of all plant tissue is the product of air and water, with only 2 per cent contributed by soil elements.

In normal soils, plant growth is probably limited more by inadequate water supplies than by lack of any other element. A program of soil management is incomplete if it ignores water and air as vital factors in, and sources of, nutrition.

MANY ROUTES TO BETTER SOIL

In this short resume of a few of the properties of soil, we have discussed several which are vital to plant growth, yet plants in the wild have survived for centuries without any human attention to these properties. Why then bother to change them? Is not natural growth enough to meet our needs?

The answer is a qualified "No." If native soils are rich, well-drained and abundantly watered by rainfall, obviously any crop adapted to the region, whether for food or ornamental purposes, will thrive. Some improvement in plant growth of value to the gardener might result from adjustment of one or more of the soil factors just discussed, but hardly enough to repay any extra effort.

The catch is that very few of us are fortunate enough to have ideal conditions. I have checked soil surveys of five leading agricultural states to see how much "ideal" soil exists. In these surveys, top quality land was graded as #1, and the rest graded down to #10. In no state could I find as much as 10 per cent of the land that would grade as #1. Thus, even if you happen to live in one of these top agricultural states, the chances are nine to one against your having soil which does not need attention.

Chapter Digest

Soil is the most fascinating element in your garden, and it is also, for practical purposes, an easy-to-understand element. Types of soil, organic and mineral content, and the beneficial activity of soil fungi and bacteria, all bear heavily on your success with plants. With a minimum of knowledge you can make this marvelous material-soil-your greatest gardening ally.