Every soil that contains organic matter has what the experts call "native fertility." The more richly organic a soil is, the greater is its "built-in" or native fertility. (We improve this when we add sludges and other organic matter.) This is quite different from the kind of fertility that we add to a soil by the use of organic and inorganic fertilizer products. Native fertility is available over a long period of years. It is something on which the grass can draw to carry it over a period of neglect. In fact, as we know, the grasses in un-tended fields are wholly dependent on their own natural renewal of the soil's native fertility.
But we do not (or should not) rely on this native or reserve fertility for the regular nutrition of a lawn. This is particularly important with the newer, more vigorous varieties of grass like Merion or Delta Bluegrasses which, because of their extended root systems, can utilize large amounts of fertilizers. If we fertilize improperly or not at all, the grass will have to depend on the soil's natural fertility and will soon use it up.
When Merion Bluegrass first came into use, lawn men did not know that it must be provided with extra sizable amounts of nitrogen. It was not an uncommon thing for an owner to exclaim, "My Merion lawn was wonderful for two years and then it went bad. Now it doesn't look any better than a lawn of common Kentucky Bluegrass and I paid $3.00 a pound for the seed I" What the owner was observing was not a deterioration in the grass itself, but an exhaustion of the native fertility of the soil, caused by inadequate fertilizing on his part.
Present-day feeding recommendations for quality turf call for applying as much as four times more nitrogen than was recommended for home lawns in 1945. This rate of feeding has enabled owners of Merion lawns to maintain them in perfect condition without any signs of deterioration.
Revolution In The Bag
Our ideas of lawn feeding have undergone revolutionary changes during the past decade, but many old-time authorities have not kept abreast. They still recommend fertilizers that were developed twenty to thirty years ago for feeding corn and beans. It is, however, in the realm of improved feeding methods that lawn culture has made some of its greatest advances.
The importance of these changes will be clearer if we understand a little about plant foods. (Many kinds of chemical and organic fertilizers are discussed in detail, under individual headings, later in this chapter.) Actually plant foods are not foods at all, but the raw materials out of which plants can manufacture the starches, sugars, proteins, hormones and other true foods they must have in order to grow. The nutrient requirements of grasses in a lawn differ from those of most other plants. That's because lawn grasses are grown only for their leaves. We are not interested in encouraging them to produce flowers and fruit.
A grass plant is incapable of taking a substance as complex as manure and drawing it into its roots. Soil bacteria are capable of partially breaking down various plant wastes and other organic matter. No one kind of bacteria, however, is able to complete more than a part of the process. There are whole chains of different soil organisms that work on various productions of the decomposition of matter. What one has done is passed on to another which, in turn, does its work and passes on the material to a different set of organisms.
Among the most important links in this chain of organic breakdown are the bacteria that change ammonia and nitrite nitrogen into nitrate nitrogen. Grass is able to use some ammonia, but growth is better if the ammonia has been fully changed into nitrate form.
All this is being emphasized because it has an important bearing on what happens to so-called natural manures—sheep, cattle, horse or sludge—when these are applied to a lawn. Most lawn-makers insist that these are best because they do not "burn" the grass. This short-sighted line of thinking is furthered by uninformed garden-store clerks who find it easier to always nod in agreement and sell what the customer asks for than to take the time to inform themselves about good lawn practices.
The Mechanics Of Organics
Here is some much-needed light on the organic fertilizer question: Bacteria are sensitive to both heat and cold. While high heat will kill them, temperatures as low as 60 degrees below zero will not. However, even a mildly cool temperature will hinder or stop their growth process. No matter how pleasant the day may seem to us, if the soil temperature is not above 60 degrees (above zero) practically all bacteria are dormant and not working on organic matter. This effectively stops all breakdown of protein. The rate of food release is slowed and the life of the soil goes into a state of "suspended animation."
Grasses continue to grow, however, at much lower temperatures. In spring, for example, some grass varieties will resume activity the minute a thaw occurs, even in soils as cold as 33 degrees above zero. And the grass keeps right on growing and consuming nitrogen in fall after the soil temperature cools off to the point (60 degrees) at which nitrogen-forming bacterial action drops off. What, then, does the grass live on during these cool-soil periods? It must get by on the supply of available nitrogen left over from the warm-soil-period activity of the bacteria—until soil readings go above 60 again. But —and here's the key fact—this is the case only if the sole source of food is organic matter.
In the wild a heavy covering of grass can be maintained by this cycle of decay and renewal. The rich prairie soils of the United States, which in colonial days began west of Cleveland and extended out until they met the semiarid land of the Great Plains, were built up by eons of just such natural soil improvement. In order to make this system work, a soil must contain both clay and organic matter. The clay acts as an adsorbent for both moisture and food elements and the organic matter supports the vital bacteria. While organic matter will adsorb and hold the same elements as clay, the bond is not as tight and the elements might disappear by spring if it were not for the clay particles.
Such a system of natural, cyclical self-renewal will not, of course, work for the home lawn. The need for a closely-clipped turf and the demand for a strong green color from early spring until freezing weather cannot be met without additional supplies of nitrogen. And, as just indicated, organic fertilizers are not reliable year-round sources of nitrogen.
Chemicals To The Rescue
This is where chemical fertilizers come into the picture. These are not complex organic compounds but simpler materials, much closer to the elements which plant roots are able to extract directly from the soil without the need for decay processes. Chemical materials are ready to go to work almost as soon as applied to a lawn, without dependence on soil temperature.
Because much of the extraneous matter is eliminated, chemical fertilizers are far more powerful, pound for pound, than the so-called natural fertilizers. This means they cannot be used carelessly. Most of them are salts and have a strong need for water, so if used in excess they will actually suck moisture directly from plant tissues with which they come in contact. This causes the so-called burning of tissues.
No one denies that chemical fertilizers as a whole (with certain exceptions to be discussed later) will burn if they are used carelessly. But since the burning is caused by their need for moisture, all that you have to do is dissolve them either before or immediately after application with liberal amounts of water; then they will not burn.
A Subtle Burn
Here's an important point: natural fertilizers, under certain conditions, will also burn plant tissue. But the home gardener rarely recognizes an organic fertilizer burn when he sees one. Much to the dismay of the gardener who uses natural manures, he may suddenly see his lawn wilt and turn brown in mid-June or early July. Usually this damage follows a period of very lush grass growth which was stimulated by a heavy application of sewerage sludge or other organic plant food. The burn is caused by excess nitrate nitrogen, which started originally as organic matter. If the soil is cool, the organic material cannot be used by the grass plants because bacteria are not sufficiently active to break it down. With the coming of hot weather these organisms get busy and break down protein at a tremendous rate. If the lawn is loaded with sludge, etc., the decay process builds up an excess of nitrogen and a soft unhealthy growth is stimulated. As the excess protein nitrogen is converted into nitrates, the grass is burned just as it would be by an excess of inorganic (chemical) nitrogen.
Years ago, recognizing that natural manures did not feed grass adequately in early spring (the time of heaviest growth) or in late fall, turf specialists began to rely more and more on pure chemicals. By making light applications at frequent intervals, they could supply the grass with exactly what it needed at the time of greatest need. Soon golf-course greenskeepers, then home lawn-owners, climbed on the chemical fertilizer bandwagon. But it's only the beginning; these materials can and should be used to much greater advantage. All that is needed is a better understanding of the plant foods grass should have, and how much of these food elements each kind of fertilizer can supply.
The Major Elements Tell-Tale Numbers
But first it is essential that you understand fully the meaning of the three numbers (such as 5-10-5) that always appear on bags of chemical fertilizer. The numbers represent the three major plant food elements. The first number stands for nitrogen (N), the second for phosphorus (P) and the third for potash or potassium (K). Each number indicates the percentage of that element in the fertilizer formula.
Thus in a 100-pound bag of 5-10-5 there are 5 pounds of nitrogen, 10 of phosphorus and 5 of potash—a total of 20 pounds of the three major plant foods. (Most state laws require that a fertilizer contain at least 20 per cent available plant food.) The remaining 80 pounds in the bag are filler or carrier materials, for easy, uniform application.
In the parlance of a fertilizer man, the first number indicates the percentage of "actual" nitrogen. In other words, a 100-pound bag of 5-10-5 actually contains only 5 pounds of nitrogen; a 50-pound bag contains 2½ pounds, etc. So you have to apply 100 pounds of a 5-10-5 mixture to a given lawn area, say 1,000 square feet, in order to apply 5 pounds of actual nitrogen. Incidentally, I cited 5-10-5 as an example merely because it is such a familiar fertilizer formula; it is not, as I'll explain later, a good lawn formula.
Nitrogen is far and away the most important fertilizer element for grasses. It is the key to vigorously growing, rich green grass blades. How much nitrogen can a mowed turf use with profit? I have checked the leading turf research centers all over the country and find that, in their experiments, growth improved in almost direct ratio to the increase in the nitrogen supply during the season—up to 8 pounds of actual nitrogen per thousand square feet of lawn area. After 8 pounds, the grass seemed to have had its appetite saturated and no further growth benefits were noted.
Grass also needs some phosphorus and potash for sturdy root and crown growth. Without enough phosphorus, for example, the grass plant cannot produce a truly winter-hardy crown. The amount needed, however, is very small. All the phosphorus used by a 2,000 square foot area of turf could probably be contained in a teacup. The need for potash is even less-. Here we begin to see the absurdities of the old-time lawn fertilizer recommendations such as 5-10-5 and 4-12-4. A common recommendation for applying 5-10-5 on lawns is 20 pounds per thousand square feet. At that rate the lawn would receive 1 pound of actual nitrogen per thousand square feet (good grass needs at least 4 pounds), 2 pounds of phosphorus (the need is for about an ounce or so) and 1 pound of potash (the grass requires about an ounce).
The Right Amount
If all these elements were water-soluble, they would eventually be washed out of the soil, and more would be needed soon. This is not the case, however. Nitrogen is soluble and soon disappears if not used by plants or bacteria. But phosphorus almost always becomes chemically bound in an insoluble form and can be pried loose only by the action of rather strong acids. I have seen lawns which have been dosed religiously every spring with 5-10-5 or 4-12-4, and as a result were so high in phosphorus that they could have served as a low-grade phosphate quarry 1 Yet in these same lawns the shortage of nitrogen was obvious.Grass does need plant foods other than the three major elements. Calcium, sulfur, iron, magnesium, manganese and other essential growth chemicals, called minor elements, are needed in small amounts. Usually, most general mixed fertilizers supply these today in adequate quantities. They are discussed later in this chapter.
The weakness of old-time fertilizers has been mentioned. We cannot blame our fathers for making these mistakes: they were doing their best. With no research on grass to guide them, they merely picked up fertilizers recommended for farm crops and used them on lawns. Because these products did do some good, they were accepted.
When, however, true research on grass got under way, the picture changed in a hurry. Up, up, up went the nitrogen applications, often to the limits of turf to absorb them. However, the tendency of fertilizer salts to burn kept a rein on the amounts that could be applied at one time. Only repeated applications of small amounts, usually dissolved in water, could be used, a process which discouraged the home gardener who could not give full time to lawn care. Only the man who made a career out of turf could really profit from these new discoveries.
The Key To Success
During this time, laboratory workers were giving more and more attention to a chemical produced experimentally years before. During the late 1930's, I remember talking with the head of fertilizer research for Swift & Co. In a test tube, he mixed some urea with formaldehyde. The first time he did so, the mass turned as hard as leather, but a second batch was quite a bit softer.
"When we learn to control that reaction," he declared, "our problems in using plant foods without burning will be solved."
Later, I came to know this material as "uraform"—a soft plastic produced by the reaction of urea and formaldehyde. The scientists knew that if it could be made soft enough it would, when applied to soil, break down slowly, releasing a little of its nitrogen each day, "spoon feeding" plants with this vital element at a rate that would not burn. Later, because of persistent mis-spelling of the original name, this chemical was given its present name, "urea-form." After years of effort it was perfected, and today this "plastic" fertilizer material is quite generally distributed, under various trade names.
Since this chemical is the key to modern lawn nutrition, a description of what it is and what it can do is essential to understanding the amazing progress it has brought about.
Ureaform, like regular organic fertilizers, is quite inert in the cold soil of early spring. It does let go of small amounts of nitrogen, however, probably from the fine dustlike particles clinging to the larger grains of plastic. As the soil warms up, the combined effect of moisture and bacterial action causes the plastic to slowly release its food. Under ideal conditions, a single application lasts about 6 to 8 months, releasing nitrogen at a uniform rate throughout its life. This period roughly covers the active growing season of most northern lawns. Early in my research with this material I had one formulation (possibly a little too hard) which showed a nitrogen response for 13 months following application—from April of one year well into May of the next. Incidentally, in order to test the safety of ureaform I piled this particular application in a line an inch deep across a test plot and left it there overnight. The next day, this was raked out and washed into the turf. There was no trace of burn from this severe test.
A Hurdle Cleared
The major weakness of these miraculous new forms of nitrogen, as I mentioned earlier, is that they resemble organic matter in their dependence upon bacteria for much of their availability. They do not begin to feed the grass until soil temperatures go above 60 degrees.
The scientists found the obvious answer; they combined urea-forms with quick-acting chemical nitrogen. Now we have turf foods that (1) do not burn, (2) feed turf throughout the growing season with a single application, (3) can be applied at a rate to supply 4 pounds of actual nitrogen and (4) cost no more than equal-strength regular fertilizers.
To repeat, no two soils are alike, and no two lawns combine the conditions found elsewhere in exactly the same pattern. Any fertilizer formula, no matter how carefully "engineered" it may be, is a compromise between the lawn's needs and the chemical components.
Fortunately there is general agreement that a fertilizer for fine turf grasses of high quality should supply a minimum of 4 pounds of actual nitrogen to 1,000 square feet of turf. The owner should distribute that 4 pounds so it will supply its nutrients throughout the entire growing season of the lawn. As a standard, a 2O-S-5 fertilizer, with at least half of its nitrogen in ureaform, was developed by one research program. This formula contains enough phosphorus to supply all of this element needed by grass. In most soils it would also supply adequate potash, provided the soil contained a fair amount of organic matter. On sandy soils, perhaps a light feeding with potash would be needed every other year to supply this element, but few lawns are made on light sands. For this reason, the 20-5-5 formula, readily possible with ureaforms, comes close to meeting the specifications of an ideal lawn fertilizer.
Few manufacturers, however, want to produce such a one-purpose product, a product that is strictly a lawn fertilizer. The formula, for example, is too low in phosphorus to make it ideal for flowers or vegetables. Since most dealers want something they can sell to everyone, there are few 20-5-5 lawn foods on the market.
For this reason, it will be easier to find ureaforms with lower amounts of nitrogen, such as 10-8-6 or .12-5-4. These will supply more phosphorus and potash than the grass can use, but these elements do little harm when present in excess, so are merely wasted.
In using these weaker forms, perhaps the best method is to apply them at a rate that will provide 2 pounds of actual nitrogen per thousand square feet, and figure on adding the rest of the requirement by watering with a solution of ammonium sulfate in summer.
This does not mean that where ureaforms are unavailable (and they are not sold everywhere) that old-time fertilizers cannot be used to grow good grass. They can be used but much more material must be handled and both phosphorus and potash are supplied in excess of normal needs. And you pay for a fertilizer according to the units of plant food it contains (nitrogen is the costliest major element). If older formulae must be used, they should be applied at four periods throughout the spring and summer. The actual dates are not too important, but, to fix the seasons in mind, I recommend that you think of four holidays—St. Patrick's Day, Memorial Day, Independence Day and Labor Day.
The first application goes on as early in spring as possible, as soon as you can walk on the turf. St. Patrick's Day is merely a convenient date for reference. This feeding should provide (as should all three successive applications) 1 pound of actual nitrogen to 1,000 square feet (you'll need 8 to 9 pounds of a 12-5-4 mixture). This can even be applied on top of late snow in spring. This first application need not be watered in. The successive applications are then made around Memorial Day, Independence Day and Labor Day. Each feeding is at the same rate as the first, but these last three are watered in.
A third method can be used where regular fertilizers and urea-forms are available separately, but not the newer mixed products which also supply phosphorus and potash. The method is simply to combine the old and the new. Use 20 pounds of a 5-10-5 (or 25 of a 4-12-4) as early in spring as convenient. Over this apply 8 pounds of ureaform. The old-time fertilizer supplies the quick-acting nitrogen and other food elements, whereas the ureaform supplies the slow-release nitrogen.
What about organic fertilizers such as cattle or sheep manure or sewerage sludge? Recent studies in plant diseases have indicated that these materials tend to foster certain turf fungi such as leaf spots and snow mold. They do not always do so, of course. However, where the grasses are likely to remain damp late in the day, where winds do not have a free sweep, or where other conditions favorable to fungi exist, an organically-fed lawn will always be rather susceptible to disease. In such sites, to avoid these fungus troubles as much as possible, use only chemical plant foods.
On the other hand, organic matter is recommended highly for working into the soil—but that is an entirely different thing. When the material is buried, the only fungi that can attack it are types that live in the soil and digest dead organic matter. Rarely do these infest even weakened grass plants, although occasionally they do. Generally, these fungi are beneficial, not harmful.
It is the mass of decaying organic duff on the surface—clippings, leaves, sludge-type fertilizers and similar rubbish—that forms a veritable incubator for many fungus spores. This is the thing to avoid.
Building Up In Sand
In sandy soils, a different problem exists. Here, sharp drainage takes off moisture so rapidly that fungi don't have a chance. Organic matter, instead of remaining on the surface in a matted layer, is absorbed rapidly by the sand. The disappearance of peat moss, compost and other forms of humus in sand is amazing.
Let me describe a method for stopping this downward flow of all essential organic products in sand. I worked this out in Florida, where gardeners in sandy areas complain that "compost put on the surface at night is gone the next morning." That is gross exaggeration, of course, but it does reflect the irritation the lawn-owner feels. Here's the procedure: Dig out the entire area that is to be made into a lawn to a depth of 12 inches. Then cover the bottom of the excavation with saturated felt. (The 15-pound weight builders use between floors is perfectly satisfactory.) If weeds, hay, cut grass or other vegetable trash is available, cover the felt with a 2 inch layer of this. Then replace the sand. (If the lawn area is large, the digging and felt-laying can be done in sections.)
The felt acts as a temporary barrier to the drain on humus-forming materials. These will work downward only as far as the felt, then start to back up into the zone above the felt. Soon grass-plant roots and other wastes fill the spaces between the grains of sand, and a good lawn soil is created. The felt decays eventually, but before it is gone, hair roots have formed a heavy mat throughout the 12-inch zone which will guard against further wholesale loss of organic matter. I hope none of you ever has to use this laborious method of lawn-making—but there it is if you need it.
The Minor Elements
About the only minor element needed by grasses in any quantity is iron. True, traces of other chemicals are vital to growth, but usually a mixed fertilizer will supply all of these required. Iron sometimes is lacking to a point where the grass does not develop a healthy green color. This can happen, even if the supply of nitrogen in the soil is adequate, if you have limey soil with a high pH which tends to lock up this element.
The new chelated irons (forms of iron that do not lock up or disappear as readily as other forms) can be very helpful if used according to manufacturers' package directions. For those of you who like to fool around with chemicals, or who just want to be 100 per cent "do it yourself" gardeners, there is an alternate— homemade ferrous ammonium sulfate. This can be prepared cheaply by mixing equal parts of ferrous sulfate (copperas) and ammonium sulfate (the common fertilizer ingredient). A handful of this mixture in a 10-quart pail of water, stirred well, forms a solution that can be applied with a fine rose-type spray through a sprinkling can. The turf will green up overnight in a dramatic way.
Let me warn against using this procedure where enough free iron is already present in the soil; that is, where the grass already has a rich green tone. I have had grass turn so dark after treatment that it looked black and most unattractive. On one occasion I helped some high school football rooters write the name of their school in the turf on their rival's football field—in 10-foot letters— simply by "watering-in" the letters with ferrous ammonium sulfate two days before the game. No matter how closely their rival's greens-keeper mowed the turf, the dark-grass letters stood out like a neon sign against the surrounding green.
Practically any minor element deficiency, if one is suspected, can be cured with a light application of dried blood—about 5 pounds to 1,000 square feet. This fertilizer contains every major and minor element needed by grass for growth, in a readily available form. It does not present the same problem as more durable forms of organic matter, since it is highly soluble and disappears before fungi can build up. For this reason, even where the owner suspects that disease may be causing a turf discoloration but is not sure that a deficiency can be ruled out, an application of dried blood can be tried.
Notes On Fertilizer Materials
Although several of the more important products and materials— natural and synthetic—used as sources of plant nutrients have been mentioned, a more complete list is offered here for your ready-reference. It will be helpful, too, in situations where an alternate for a "just-right" but unavailable product must be found. For example, the mixed ureaforms, although readily available in large cities like New York, Detroit and Chicago, may be hard to find in a smaller community.
It is impossible, however, to catalog all the materials ever used for feeding grass plants. Practically everything of an organic nature containing protein, phosphorus or potash has at some time or other been used on lawns. Human bones have been ground up as a source of phosphorus. Omar Khayyam speaks of the contribution of the human body to the nutrition of the rose. A less gruesome but still unusual fertilizer was the pair of old trousers discarded by the laird of a certain Scotch manor and salvaged by the gardener to bury under a row of prized leeks. Wool, being largely protein, is an excellent fertilizer; wool combings or noils have been used for centuries. Other organic materials include feathers, leather scrap, slaughterhouse floor washings and horn shavings. Clay's Fertilizer the scrapings of British privys, revered by generations of gardeners trained in the British tradition—is matched and surpassed in the United States by the activated sewerage sludges which are the most widely-sold of all organic lawn fertilizers.
In the field of chemicals the range is not as wide, but the potency, pound for pound, is much higher. For example, a high-grade dried blood might contain as much as 14 per cent nitrogen. This grade would, however, be so valuable that it would probably be sold for animal feed, for blood albumin glues or some other purpose where a higher price would prevail. In synthetic forms of nitrogen, we can today find analyses as high as 52 per cent.
Faced with making a choice among these myriad products, the homeowner may be completely at the mercy of some not-too-well-informed salesman. He is limited in his choice of materials to those that can be applied on the surface of the lawn (if it is already in existence) and which will not be too conspicuous when applied. This rules out many uncomposted materials like feathers, cotton noils or fresh manure.
Commercial Organic Fertilizers
Here is a rundown of some valuable and commonly available commercial organic fertilizers:
Dried Blood: Contains 8 to 14 per cent nitrogen; fertilizer grades seldom exceed 9 per cent. Best possible source of minor elements in soluble form. Must be used with care as it becomes available almost as rapidly as a chemical source of nitrogen, so that an overdose will cause a burn very quickly in warm soils. It leaves very little organic residue.
Liquid Fish Fertilizer: The fish "emulsions" are similar to dried blood in that practically all their food elements are in soluble form. They do contain some fish blood. These products are made by soaking the offal (from fish canning and freezing) in large tanks to extract all soluble plant food elements and then condensing these so highly that bacteria cannot work on the finished product. Although expensive, fish emulsions contain many minerals and are excellent lawn fertilizers. They do not smell as fishy as might be expected.
Tankage: Varies so much it cannot be relied upon as a fertilizer. It often contains fats that are not desirable. Good tankage brings such a high price as animal feed that the leftovers used for fertilizer grades are pretty poor stuff.
Steamed Bone Meal: Although usually used as a phosphorus fertilizer (it contains about 23 per cent of this element), steamed bone meal also has 1 to 2 per cent nitrogen. It is perhaps the most overrated of all lawn fertilizers. The phosphorus is in an extremely unavailable form: it may remain unused for a generation or more. Much of the reputation of today's steamed bone meal has resulted from the successful use of fresh ground raw bone meal a century or more ago. That reputation has been handed down to the entirely different product of today. Don't waste money on bone meal for lawns!
Horn Shavings and Meal: Also includes horn and hoof meal. If natural horn shavings can be had, they make excellent fertilizer (10 to 14 per cent nitrogen) but the supply of this material is usually snapped up by florists.
Dried Ground Fish: Contains about 6 to 10 per cent nitrogen plus 4 to 8 per cent phosphorus. A good fertilizer, if it doesn't cost too much. Feed manufacturers take up the supply.
Pulverized Sheep and Shredded Cattle Manures: These two products—both highly overrated—are made from the sweepings of railroad cattle cars and pens in the stockyards. Although quite variable in composition, the manures can be depended upon to contain 1 per cent each of nitrogen, phosphorus and potash (the usual guaranteed analysis on the bag). At current prices, this makes them the most expensive source of nitrogen available on the market—about $2.50 a pound. To supply the 4 pounds of actual nitrogen per 1,000 square feet needed by fine turf, the lawn-owner would have to spread 400 pounds of shredded sheep manure onto a 20 by 50 lawn!
Sewerage Sludge: Since the No. 1 seller among organic lawn fertilizers is sewerage sludge, it should be examined critically for its good and bad qualities. Commercial processed grades deliver nitrogen at the lowest cost per pound of any organic fertilizer generally available. Air-dried sludge, the waste product of a sewerage disposal plant, can often be had for the hauling. In fact, it is such a nuisance at times that some small villages are even willing to pay to have it hauled away.
It contains about 4 per cent nitrogen, a modicum of phosphorus and practically no potash. In big cities, where synthetic detergents are now widely used, the phosphorus content has crept up to about 1 per cent, although the solubility of these liquid "soaps" is so high that very little phosphorus is deposited with the sludge. This has, however, dropped the already small percentage of potash in sludge.
The biggest objection to air-dried sludge, other than its potential of encouraging turf diseases, is its odor. When dry it is fairly respectable but when wetted a real stench develops, enough to alienate the neighbors for weeks. The processed sludge fertilizers produced by various methods are somewhat higher in nitrogen. The odor is not as serious, although a lawn treated with one of these fertilizers is far from a bed of roses I
One fact should be kept in mind which affects the value of the air-dried forms of sludge. Because they contain fecal matter out of sewerage, they are usually infected with amoebae. While air-drying and freezing over winter will kill the non-cyst-forming types of these intestinal parasites, the cyst-forming type—the worst form—is not killed. Never handle air-dried sludge with the bare hands. Be sure that the drainage from a lawn treated with raw or air-dried sludge does not lead onto a vegetable garden.
Turf Disease Factor
Some plant pathologists blame the increase in turf diseases on the use of sewerage sludge, pointing out the role it plays in feeding the organisms of snow mold, septoria and helminthosporium leaf spots and pythium. It is true, of course, that these organisms thrive on sludge: one big research laboratory uses activated sludge as an ideal culture medium on which to grow its type species. However, sludge is no worse than other organic materials in this respect: it is just that more sludge is sold than any other natural fertilizer.
Despite these drawbacks, sludge must be considered a basic lawn fertilizer. It is a cheap source of organic matter, even though it is necessarily a poorer producer of true humus than are straw, sawdust or other woody materials containing a higher percentage of lignin. When plowed under in preparing a new lawn, not enough remains on the surface to feed fungus organisms to any extent.
One fact overlooked in recommending sludge fertilizers is that practically all of the water-soluble minerals are washed out of them. Any soluble nutrients in the sewerage that can be dissolved go out with the run-off water, leaving only insolubles to settle out. This is the reason that sludges are such "hard starters" in early spring. With practically no soluble nitrogen in them, they produce little response until really warm weather sets in, after which they release nitrogen very rapidly. I have seen many cases where the lawn-maker used sludge early in spring and, seeing no results, applied it again. Naturally, this made no difference either, so he applied another dose a while later. Then, in June, with the coming of the warmer weather, the lawn "popped" from the heavy overfeeding with nitrogen and burned so badly it had to be rebuilt.
This danger is increased by the fact that grass, unlike other plants, is unable to ration its nitrogen intake. Most other plants will balance their feeding if everything needed for growth is present. Grass, however, will suck up nitrogen until the tissues of the leaf are gorged with it.
If sludges are used as lawn fertilizers, supplement them with a quickly-available form of chemical nitrogen to feed the grass early in spring. Also, add a little muriate of potash, since that element is so low in sludges.
Avoid the use of sludges on shady lawns under trees. Practically every severe case of snow mold I have examined in the past few years was sludge-fed.
Wood Ashes: If not leached by rains, these contain between 3 and 7 per cent potash plus a trace of phosphoric acid and about 30 per cent calcium. While messy, they are a fair source of potash from an "organic" source. These are worth using only if available free.
Leaf Mold: If not too high a price is paid for it, leaf mold might be considered a low-grade nitrogen source. It is at least as good as commercial sheep or cattle manure, and much cheaper. It is, of course, a valuable source of humus for plowing under.
Peat Moss: Like leaf mold, peat moss is a soil amendment rather than a fertilizer, even though it is almost as good a food as commercial sheep manure. However its nitrogen is "bound" and becomes available very slowly.
While the list of chemical fertilizers is much shorter than that of natural manures, the chemicals today are used much more widely. It was the development of these chemical plant foods that freed us from the lawn-growth restrictions imposed by the unavailable nitrogen tied up in protein in natural manures. Today, our ablest soil specialists recognize the importance of quick feeding with chemicals, at least in those seasons when protein cannot be broken down in the soil. But they also emphasize the need for constantly increasing the humus content so that these chemicals will be really effective.
The characteristic which distinguishes most chemical plant foods is that they are more highly concentrated than natural manures. This means less weight to handle in doing a given job. Organic substances must be broken down by bacteria before they become useful to plants. Chemicals, as a rule, are ready to go to work as soon as they dissolve.
The following list presents a number of different fertilizer chemicals and describes how they are used, how they perform, what role they play in plant nutrition, and so forth. This is meant—as they say in fancy inter-office memos—"FYI": for your information. In actual practice, you will obtain and use most of these chemicals in premixed, packaged compounds, with full directions for proper application.
Sulfate of Ammonia: This is sometimes written ammonium sul-fate. A by-product of coke and gas manufacturing, this nitrogen-bearing fertilizer is produced in vast quantities. It contains about 20 per cent nitrogen. Due to its sulfur component, it has the disadvantage of increasing soil acidity, which should be taken into account where soils are already "sour." However, this need not be a drawback if proper attention is paid to the pH factor (discussed in the following chapter). Sulfate of ammonia is probably the most readily available source of low cost nitrogen. You should never try to apply it to a lawn in dry form but should dissolve it in water and apply it either through a hose-siphon device or with a sprinkling can. Five pounds of sulfate of ammonia dissolved in SO gallons of water will supply 1 pound of actual nitrogen to 1,000 square feet of lawn area. This is about the maximum amount of quickly-available nitrogen that should be applied at one time. Even this should be washed in with an extra sprinkling as soon as put on.
Urea: This is one of the most concentrated of all nitrogen fertilizers, with an analysis of 42 to 45 per cent. It leaves no appreciable residue. Urea is one of the best of all lawn fertilizers but should be used with caution because of its high concentration. For safety's sake, not more than 1 pound to 20 gallons of water should be used.
Ammonium Nitrate: This is now being manufactured in pelleted form so it can be handled more safely. It contains about 36 per cent nitrogen, making it a powerful fertilizer. An application of 3 pounds to 1,000 square feet is enough for a single feeding. If not in pelleted form (which allows it to drop without sticking to the leaves) it should be used only in liquid form.
Superphosphate: This is by far the cheapest source of phosphorus available today, and the only one generally available in garden centers (other than bone meal). A generous application (up to 50 pounds to 1,000 square feet) should be worked into the new lawn before seeding. Phosphorus does not move through the soil readily. By plowing under a supply before the new turf is started, you can be sure that when roots penetrate into the soil there will be enough of this important element for them to feed upon.
Ground Phosphate Rock: Occasionally, ground phosphate rock can be had from dealers in farm supplies. While it is not as readily available as superphosphate, and is less efficient pound for pound, it is usually quite cheap and can be used for plowing under before seeding. About 75 pounds to 1,000 square feet will be needed. This will become slowly available when rotting roots form tiny acid pockets, but will lock up again if not used.
The season-to-season requirements of lawns for phosphorus are best supplied by the use of mixed fertilizers applied to the surface, but a reserve of this element in the soil itself can last as long as half a century.
Muriate of Potash and Suljate of Potash: Either of these chemicals can be used where additional potash seems to be needed. Natural shortages of potash in the soil are most likely to occur west of the Mississippi, on prairie soils that never supported woody growth. However, additional amounts of this element are practically never needed where the grass clippings are allowed to remain on the lawn.
Chips Off The Chapter
- Organic and inorganic fertilizers play different roles in grass plant nutrition. An understanding of how they function will help you to use each kind to maximum advantage. Chemicals become available quickly, are usually used up by the plants or leached out of the soil quickly. Natural fertilizers must break down into usable form, thus they are slower in starting but longer lasting.
- The meaning of 5-10-5 on a package of plant food. Of all the fertilizer elements, both major and minor, nitrogen is most essential in a lawn's diet.
- Ureaform—marvel of marvels—is a "plastic key" to turf feeding.
- In applying lawn fertilizers, "when" is almost as vital as "what."
- There's great variety in plant food materials: check the check-list.