Soil-The Life Of Your Lawn

This chapter includes much practical information about soil, specifically topsoil. But first, since soil is a most important element of success with lawns, let's take a quick look at it. An understanding of this amazingly complex "community" that lies under the greensward of a lawn will explain why many things that have been or will be recommended are important.

Take a spade and dig out a clod of soil. It looks unimportant and certainly lifeless, unless a disturbed earthworm happens to wriggle out. Yet in your shovel you hold a community which probably contains more living "individuals" than there are human beings on earth. Bacteria, fungi, protozoa and other microscopic life by the billions find a home in a single clod of topsoil.

Without these living organisms, we have a lifeless mixture of clay, loam and sand, something which cannot truthfully be called a soil. But with these living organisms the lifeless minerals become the basic stuff of life—soil.

Converting Fertilizers

Bacteria and fungi are vital to soil because of their role in feeding plants. Actually, the fertilizers we apply do very little direct feeding. Although grass roots may build up tremendous masses of fibrous hairs, these can come in contact with perhaps less than one soil particle in a million. A soluble nitrogen applied to a soil would therefore be only about one-millionth efficient—that is, if it were not for bacteria. If the soil is suitable for growing grass, it probably contains enough of these microscopic forms of life so that practically every grain of soil has one or two organisms clinging to it.

As simple as these globs of life seem, they are actually plants that have somewhat the same food needs as higher forms of vegetable life. But since bacteria and fungi have no chlorophyll, they do not manufacture starch and must get this energy food by digesting organic matter. To support life while doing so, they need the same nitrogen, phosphorus, potash and minor elements as do higher plants.

When fertilizers are applied in excess of the needs of the grass in the lawn, they are quickly absorbed by soil organisms and used for food. This is not lost, however. All these microorganisms have short life spans, often a matter of hours. As they die, they release the plant foods they absorbed. By this time, a root hair may have reached into that soil area, and this released food becomes available to the root and thus to the grass plant.

I realize this is a simplified picture of the bewildering and complex world of the soil. It does give some idea how these seemingly unimportant creatures are the savers and conservers of plant foods that might otherwise be lost. This is the reason why organic matter is so important in soils, and why we must do everything we can to build it up as a home for the billions upon billions of bacteria that a lawn soil requires.

Wonderful Humus

The breakdown of some kinds of organic matter produces a substance called humus. Not all organic matter does so; only those materials that contain lignin, the substance found in woody cells, will produce humus. Humus is a lignin "complex." This excludes such organic materials as dried blood, flour and many meat and fish products. These decay more completely than do lignin-plant residues, and so do not leave the essential rot-resistant residues.

Animal manures and sewerage sludge are halfway humus formers. Both contain fecal matter (which decays without much residue) and lignin which leaves a humus residue.

Humus is organic matter that has reached a stage of stabilization where it no longer decays rapidly and in which there are no starches or sugars. It does continue to break down, but very slowly, releasing about 2 per cent of its tightly-bound protein a year. This means that a single application of humus may continue to feed a lawn for fifty years or more.

I have not made any attempt to define humus more exactly. It is one of the great mysteries related to the subject of soils. Dr. Selman Waksman, who has contributed so much to our knowledge of antibiotics, and who discovered several of the "miracle" drugs, was originally a soil scientist. Years ago he wrote a book (of over 900 pages) that deals entirely with humus. In the end he left as many questions unanswered as he settled. Anyone who thinks of soil as the "dirt beneath his feet," would do well to read this amazing volume.

So far, we have looked at soils largely as they contribute to the mineral nutrition of grass. Equally important is their role in supplying water and air. It might even be said that air and water are more important than mineral foods, since over 95 per cent of the weight of a grass plant is derived from air and water. Actually, however, it would be more accurate to liken mineral nutrition, water and air to a three-legged stool—remove one and the whole organism is upset.

Condition Counts

At the same time, the "condition" of soil, which determines its ability to supply air and water, is all important. Here we might pay a tribute to the Monsanto Chemical Company which, through the introduction of its chemical, Krilium, made the gardening public aware of the importance of soil conditioning. The attention this product drew to the need for free movement of air and water was a major step in our thinking about soils.

Actually, soil conditioners are not new. Pliny in ancient times mentioned lime for exactly the same purpose for which today we might use a chemical soil conditioner—and at much greater cost. Add a particle of lime to a soil particle that is sticky and impervious to water and it will immediately draw to it eight particles of clay. The lime and clay will be held together by an electrical attraction which (in theory at least) will make a lime-treated soil eight times as permeable by water and air as a soil not so treated.

Thus by plowing a layer of limestone screenings into a clay soil, we can improve it enormously for lawn purposes. The question of pH (the alkaline-acid balance of the soil, which is fully discussed in Chapter 5) does not enter into the problem since the trillions of clay particles in a cubic foot of clay soil are capable of buffering enormous amounts of lime. Not until we apply one-eighth as many particles of limestone as there are particles of clay will pH become a problem.

Organic Amendment

Organic matter, too, is a soil conditioner, and one of the best, but, compared with limestone, it forms such a weak bond with clay that larger amounts are needed. However, organic matter has the added advantage of being able to condition sand as well as clay. Another advantage it has over lime and other non-organic soil amendments is that it also provides a home for bacteria, releases plant food over a long period of time and acts as a high-capacity sponge for water and nutrient solutions.

The use of soil amendments is much more important to lawns than to flower and vegetable gardens because a lawn cannot be plowed up every year. Once the grass is established, the underlying soil becomes all but inaccessible for further amendment. While it is possible to roll back the overlying sod and do something about a poor soil, this is a desperate measure which few of us care to take. Our only practical approach is to feed the grass to encourage strong root growth, so the roots, in decaying, will build up the soil's humus content.

The "Black Dirt" Question

There are many other aspects of the question of soil conditioning and amending. One "aspect," which might be funny if it weren't so expensive, is that for some strange reason many a lawn-maker feels that all his soil improvement problems will be solved if only he can buy and apply a few loads of "good black dirt." In his mind he pictures a rich, friable, black loam that he can spread like a magic carpet over his lawn-to-be. This will permit him to produce a covering of velvety grass almost without effort.

Unfortunately, this happy dream doesn't materialize with the purchase of "good black dirt," at least not in about 995 cases out of 1,000. The chances are great that the gritty mass of black stuff dumped onto his property will bring with it millions upon millions of weed seeds, probably many of them species not even growing in his area. No matter how blatantly the seller may advertise his wares as "weed free," don't believe him I There is only one way to be sure soil is actually free of all forms of harmful life and that is by steam sterilization, permeating the soil with live steam under pressure for at least one hour. Although I have probably seen as many loads of black dirt delivered as most men, I have never known personally of a firm or individual that sold soil actually treated by this method. Steaming is common practice in greenhouses, where special pipelines are rigged to allow live steam from the boilers to seep through the soil in the greenhouse benches. This treated soil is, however, valued so highly that few home gardeners would pay the price. Occasionally, a local greenhouse will sell such soil, for use with house plants, at $1.00 to $3.00 a bushel. But in the majority of cases, unless you are as lucky as the man who wins the Irish Sweepstakes, the "topsoil" you buy will be black soil that is full of weed seed, spores of fungi, roots of perennial weeds like Canada Thistle and Bindweed and a liberal portion of quack grass rhizomes.

Rich Color—Poor Vigor

This weed menace might be tolerable if the color of the material represented true richness. Unfortunately, this is rarely the case. Sometimes the product is treated chemically to make it dark, but usually the blackness is due to natural carbon—the same substance that gives coal its inky hue. True, many rich soils are black. The point is that not all black soils are rich. The only thing this color indicates is that the soil once contained organic matter. The decay of cells of plants and animals leaves behind a residue of carbon, which is present in every living cell. Carbon in the form found in soil is of limited value in plant nutrition. Years of crop growing could exhaust practically all fertility in a once-rich soil, yet leave it very dark in color.

I have visited many black-dirt fields, but in all my experience I cannot recall a single one that was selected because it was rich. Occasionally, when the relentless march of real estate engulfs rich farmland, the black soil it yields is available. I have observed, however, that often in such cases the soil is stripped off and sold at a premium to commercial growers. These men know good soil from fake black dirt.

A favorite scalping ground for the Black Dirt Indians is a swamp. In a swamp, exclusion of air from the soil results in the retention of the black color by the deposited organic matter. Unfortunately, lack of oxygen alters the normal—and vital—processes of decay. Thus muck soils are generally inferior to normal topsoils.

Fumigating "Black Dirt" And Other Soils

But the "black dirt problem," to be practical about it, will probably be with us always. So here's some help for those of you who have bought or will buy the product, or who have the weed seed problem in soil from other sources. The best solution is to treat the soil chemically to kill weed seeds and fungi before using it. This method of handling will not kill all such seeds, but usually gets rid of those that will sprout the first year the lawn is planted. These are the ones most to be avoided because they will offer competition to the grass when it is young and least able to resist weed invasions.

Three chemicals are satisfactory for most purposes. Perhaps the easiest of these to use is calcium cyanamid, a dull gray granular material sold under various trade names. When added to damp soil, this at first releases a heavy poisonous gas which is deadly to almost all living vegetation. Calcium cyanamid will not kill fully dormant, hard weed seeds but will kill roots of quack grass, Canada Thistle, Bindweed and all soft weed seeds that are ready to sprout. Once the poison has done its work, it breaks down into lime and nitrogen, both valuable plant foods. The one drawback is that it must be used sixty days ahead of seeding. This allows the chemical to do its work and then convert into plant food. Calcium cyanamid is effective, safe and easy to use if the directions are followed carefully—a rule, incidentally, that holds true for all chemical products.

Chloropicrin is another product that can be used, with proper precautions, by anyone. This chemical is the familiar tear gas of World War I. As can be imagined, even slightly careless use is likely to cause a weeping spell. It is sold as a liquid in containers, under pressure, but when released turns into a gas. To use, cover the pile of soil to be treated with a plastic cover, which should be at least of four-mil thickness. Seal the edges with damp soil to hold down the cover and keep in the gas. Follow directions on the can for applying the chemical. The released liquid turns to gas and penetrates the soil. After 24 hours, the covering is removed and the soil turned over with a fork to dissipate the gas. The soil should then be completely-weed free.

A third chemical fumigant is sodium methyl dithiocarbomate (Vapam and other trade names). It is not used on a pile of soil but is applied to the topsoil after it has been spread, leveled and worked up, ready for seeding. It can be applied with a sprinkling can. After application, the surface is wet down with a fine spray of water, which seals in the gas so it can do its work. This will take about one week, after which the surface is raked lightly and is ready for planting. In seeding, disturb the soil as little as possible to avoid bringing up deep-buried weed seeds that may not have been killed.

Better Substitutes

For many of you there is a better solution. Instead of black dirt, use something else to improve your topsoil. Fine cinders, already mentioned for subsoil, have no fertility value but can be supplemented with heavy applications of fertilizer. They are weed free. If sifted through a 1/4-inch mesh, they form a loose topsoil mixture with clay which will support grass roots nicely.

Spent mushroom manure is an even better material because it includes organic matter which does not introduce weeds or fungi. It is actually a mixture of the composted manure used to fill mushroom beds and the rich loamy soil used to "case" or cover them. By the time it is discarded, all the weed seeds have sprouted and fungi will find little nourishment in the organic matter which has been depleted of starches and sugars. For use in top soil, spent mushroom manure should be screened to remove large, uncomposted clods and to work it up for spreading.

Another valuable soil amendment is vermiculite. This is a special form of mica which, when heated in processing ovens to over 2,000 degrees, expands in the same way as popcorn. Since that much heat destroys all forms of life, vermiculite is completely weed free and sterile. The heating process develops a unique internal structure inside the popped mica grain. A single piece, no bigger than a man's thumb, contains microscopic passages totaling miles in length. These pores allow each particle to absorb much more than its own weight in water. Dissolved minerals are also absorbed in solution. Thus, when mixed into the soil the mica particles act much like organic matter except that they do not decay.

Let Nature Do It

There are times when the new homeowner cannot afford to treat soil chemically, nor can he spend money for substitute materials. This is a common situation in new housing developments where the father of a growing family has spent all his available money buying a home and has mortgaged future income to keep up payments. His property has probably been stripped of all the rich topsoil (if it ever existed). The subsoil dug from the foundation has been spread over the area and concealed beneath a two-inch skim of blackish soil.

If this is your situation, there are some low-cost methods you can follow and still have a beautiful lawn. One is the 3-inch-sawdust layer described in Chapter 2. Another, mentioned earlier in this chapter, might be described as nature's method. You build the lawn on pure subsoil by letting the grass plants themselves supply the organic matter which will gradually "convert" the upper layer of the subsoil into topsoil. What few gardeners appreciate is that while the crown of the grass plant is a true perennial, its roots are annual (dying off each fall, and renewing themselves again in spring). If the grass is fed heavily enough, at least for the first year or two, the mass of underground roots will build up enough organic matter to serve as an adequate breeding ground for the bacteria so necessary to a good lawn soil.

Cereal Rye As A Soil Improver

There is a third, low-cost, "natural" way to develop a good lawn soil. It is the use of cereal rye as a "green manure" cover crop. In most cases there is little opportunity to improve the supply of organic matter in soil by plowing under a cover crop. This requires a full season of growth of the crop before work on the lawn can begin since a full season is needed to permit the production of enough top and root growth to be worth the effort. Not many new homeowners are willing to wait that long. However, there are times when this method could be used to advantage, as when a lot is purchased as a future homesite.

Do not use the oft-recommended annual rye grass; it has definite disadvantages which are explained in Chapter 6. Be sure you use cereal rye. Most seed stores sell Rosen Rye in small amounts for this purpose. Sow this seed over the intended lawn area, after plowing it thoroughly, at the rate of 5 pounds to 1,000 square feet.

Sowing can be done either in spring or fall. If fall sown, cereal rye continues to grow during the winter whenever air temperatures go above freezing. Plow the crop into the soil the following spring when the tops are 18 to 24 inches tall. Then apply IS pounds of ammonium sulfate per 1,000 square feet of lawn area to help speed decay of the green manure. If the lawn is to be made the following August, keep the area cultivated until work begins: this will help destroy weeds. If the lawn is not to be planted until the following year, another crop of cereal rye can be sown immediately after the first crop is plowed under.

The improvement in soil following a crop of cereal rye is due as much to the amazing mass of root hairs produced by this plant as to the organic matter in the tops. The roots penetrate to a depth of 2 to 3 feet, bringing up deep-buried nutrients and concentrating these in the stems and leaves. Also, when the roots decay, they leave the soil honeycombed with minute tubes through which air and moisture can move freely.

I would recommend that a crop of cereal rye be grown before seeding any new lawn, provided this can be done without delaying the work of establishing a permanent turf.

Chips Off The Chapter

1. You 11 do a better job of topsoil preparation if you understand the make-up and complexity of the amazing "community" teeming with life called the soil.
2. Bacteria are the backbone. Without bacterial action in the soil the grass plants can "starve in the midst of plenty." And bacteria and organic matter go hand in hand.
3. Beware of "black dirt." It usually only adds to your troubles. But there are chemicals you can apply to make it or any other weed- or disease-infested soil usable.
4. However, there are several topsoil substitutes you may find preferable.
5. Cereal rye is an effective and low-cost soil improvement crop—if you can spare the time to let it work.

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