Once chopped, leaves occupy much less volume. My neighbor, John, a very serious gardener like me, keeps several large garbage cans filled with pulverized dry leaves for use as mulch when needed. Were I a northern gardener I'd store shredded dry leaves in plastic bags over the winter to mix into compost piles when spring gra.s.s clippings and other more potent materials were available. Some people fear using urban leaves because they may contain automotive pollutants such as oil and rubber components. Such worries are probably groundless. Dave Campbell who ran the City of Portland (Oregon) Bureau of Maintenance leaf composting program said he has run tests for heavy metals and pesticide residues on every windrow of compost he has made.

"Almost all our tests so far have shown less than the background level for heavy metals, and no traces of pesticides [including]

chlorinated and organophosphated pesticides.... It is very rare for there to be any problem."

Campbell tells an interesting story that points out how thoroughly composting eliminates pesticide residues. He said,

"Once I was curious about some leaves we were getting from a city park where I knew the trees had been sprayed with a pesticide just about a month before the leaves fell and we collected them. In this case, I had the uncomposted leaves tested and then the compost tested. In the fresh leaves a trace of ... residue was detected, but by the time the composting process was finished, no detectable level was found."

_Lime._ There is no disputing that calcium is a vital soil nutrient as essential to the formation of plant and animal proteins as nitrogen. Soils deficient in calcium can be inexpensively improved by adding agricultural lime which is relatively pure calcium carbonate (CaC03). The use of agricultural lime or dolomitic lime in compost piles is somewhat controversial. Even the most authoritative of authorities disagree. There is no disputing that the calcium content of plant material and animal manure resulting from that plant material is very dependent on the amount of calcium available in the soil. Chapter Eight contains quite a thorough discussion of this very phenomena. If a compost pile is made from a variety of materials grown on soils that contained adequate calcium, then adding additional lime should be unnecessary. However, if the materials being composted are themselves deficient in calcium then the organisms of decomposition may not develop fully.

While preparing this book, I queried the venerable Dr. Herbert H.

Koepf about lime in the compost heap. Koepf's biodynamic books served as my own introduction to gardening in the early 1970s. He is still active though in his late seventies. Koepf believes that lime is not necessary when composting mixtures that contain significant amounts of manure because the decomposition of proteinaceous materials develops a more or less neutral pH. However, when composting mixtures of vegetation without manure, the conditions tend to become very acid and bacterial fermentation is inhibited. To correct low pH, Koepf recommends agricultural lime at 25 pounds per ton of vegetation, the weight figured on a dry matter basis. To guestimate dry weight, remember that green vegetation is 70-80 percent water, to prevent organic material like hay from spoiling it is first dried down to below 15 percent moisture.

There is another reason to make sure that a compost pile contains an abundance of calcium. Azobacteria, that can fix nitrate nitrogen in mellowing compost piles, depend for their activity on the availability of calcium. Adding agricultural lime in such a situation may be very useful, greatly speed the decomposition process, and improve the quality of the compost. Albert Howard used small amounts of lime in his compost piles specifically to aid nitrogen fixation. He also incorporated significant quant.i.ties of fresh bovine manure at the same time.

However, adding lime to heating manure piles results in the loss of large quant.i.ties of ammonia gas. Perhaps this is the reason some people are opposed to using lime in any composting process. Keep in mind that a manure pile is not a compost pile. Although both will heat up and decay, the starting C/N of a barnyard manure pile runs around 10:1 while a compost heap of yard waste and kitchen garbage runs 25:1 to 30:1. Any time highly nitrogenous material, such as fresh manures or spring gra.s.s clippings, are permitted to decompose without adjustment of the carbon-to-nitrogen ratio with less potent stuff, ammonia tends to be released, lime or not.

Only agricultural lime or slightly better, dolomitic lime, are useful in compost piles. Quicklime or slaked lime are made from heated limestone and undergo a violent chemical reaction when mixed with water. They may be fine for making cement, but not for most agricultural purposes.

_Linseed meal._ See _Cottonseed meal_.

_Manure._ Fresh manure can be the single most useful addition to the compost pile. What makes it special is the presence of large quant.i.ties of active digestive enzymes. These enzymes seem to contribute to more rapid heating and result in a finer-textured, more completely decomposed compost that provokes a greater growth response in plants. Manure from cattle and other multi-stomached ruminants also contains cellulose-decomposing bacteria. Soil animals supply similar digestive enzymes as they work over the litter on the forest floor but before insects and other tiny animals can eat much of a compost heap, well-made piles will heat up, driving out or killing everything except microorganisms and fungi.

All of the above might be of interest to the country dweller or serious backyard food grower but probably sounds highly impractical to most of this book's readers. Don't despair if fresh manure is not available or if using it is unappealing. Compost made with fresh, unheated manure works only a little faster and produces just a slightly better product than compost activated with seed meals, slaughterhouse concentrates, ground alfalfa, gra.s.s clippings, kitchen garbage, or even dried, sacked manures. Compost made without any manure still "makes!"

When evaluating manure keep in mind the many pitfalls. Fresh manure is very valuable, but if you obtain some that has been has been heaped up and permitted to heat up, much of its nitrogen may already have dissipated as ammonia while the valuable digestive enzymes will have been destroyed by the high temperatures at the heap's core. A similar degradation happens to digestive enzymes when manure is dried and sacked. Usually, dried manure comes from feedlots where it has also first been stacked wet and gone through a violent heating process. So if I were going to use sacked dried manure to lower the C/N of a compost pile, I'd evaluate it strictly on its cost per pound of actual nitrogen. In some cases, seed meals might be cheaper and better able to drop the heap's carbon-to-nitrogen ratio even more than manure.

There are many kinds of manure and various samples of the same type of manure may not be equal. This demonstrates the principle of what goes in comes out. Plants concentrate proteins and mineral nutrients in their seed so animals fed on seed (like chickens) excrete manure nearly as high in minerals and with a C/N like seed meals (around 8:1). Alfalfa hay is a legume with a C/N around 12:1. Rabbits fed almost exclusively on alfalfa pellets make a rich manure with a similar C/N. Spring gra.s.s and high quality hay and other leafy greens have a C/N nearly as good as alfalfa. Livestock fed the best hay supplemented with grain and silage make fairly rich manure. Pity the unfortunate livestock trying to survive as "strawburners" eating overly mature gra.s.s hay from depleted fields. Their manure will be as poor as the food and soil they are trying to live on.

When evaluating manure, also consider the nature and quant.i.ty of bedding mixed into it. Our local boarding stables keep their lazy horses on fir sawdust. The idle "riding" horses are usually fed very strawy local gra.s.s hay with just enough supplemental alfalfa and grain to maintain a minimal healthy condition. The "horse manure"

I've hauled from these stables seems more sawdust than manure. It must have a C/N of 50 or 60:1 because by itself it will barely heat up.

Manure mixed with straw is usually richer stuff. Often this type comes from dairies. Modern breeds of milk cows must be fed seed meals and other concentrates to temporarily sustain them against depletion from unnaturally high milk production.

After rabbit and chicken, horse manure from well-fed animals like race horses or true, working animals may come next. Certainly it is right up there with the best cow manure. Before the era of chemical fertilizer, market gardeners on the outskirts of large cities took wagon loads of produce to market and returned with an equivalent weight of "street sweepings." What they most prized was called "short manure," or horse manure without any bedding. Manure and bedding mixtures were referred to as "long manure" and weren't considered nearly as valuable.

Finally, remember that over half the excretion of animals is urine.

And far too little value is placed on urine. As early as 1900 it was well known that if you fed one ton (dry weight) of hay and measured the resulting manure after thorough drying, only 800 pounds was left. What happened to the other 1,200 pounds of dry material? Some, of course, went to grow the animal. Some was enzymatically "burned"

as energy fuel and its wastes given off as CO2 and H2O. Most of it was excreted in liquid form. After all, what is digestion but an enzymatic conversion of dry material into a water solution so it can be circulated through the bloodstream to be used and discarded as needed. Urine also contains numerous complex organic substances and cellular breakdown products that improve the health of the soil ecology.

However, urine is not easy to capture. It tends to leach into the ground or run off when it should be absorbed into bedding. Chicken manure and the excrements of other fowl are particularly valuable in this respect because the liquids and solids of their waste are uniformly mixed so nothing is lost. When Howard worked out his system of making superior compost at Indore, he took full measure of the value of urine and paid great care to its capture and use.

_Paper_ is almost pure cellulose and has a very high C/N like straw or sawdust. It can be considered a valuable source of bulk for composting if you're using compost as mulch. Looked upon another way, composting can be a practical way to recycle paper at home.

The key to composting paper is to shred or grind it. Layers of paper will compress into airless mats. Motor-driven hammermill shredders will make short work of dry paper. Once torn into tiny pieces and mixed with other materials, paper is no more subject to compaction than gra.s.s clippings. Even without power shredding equipment, newsprint can be shredded by hand, easily ripped into narrow strips by tearing whole sections along the grain of the paper, not fighting against it.

Evaluating Nitrogen Content

A one-cubic foot bag of dried steer manure weighs 25 pounds and is labeled 1 percent nitrogen. That means four sacks weighs 100 pounds and contains 1 pound of actual nitrogen.

A fifty pound bag of cottonseed meal contains six percent nitrogen.

Two sacks weighs 100 pounds and contains 6 pounds of actual nitrogen.

Therefore it takes 24 sacks of steer manure to equal the nitrogen contained in two sacks of cottonseed meal.

If steer manure costs $1.50 per sack, six pound of actual nitrogen from steer manure costs 24 x $1.50 = $36.00

If fifty pounds of cottonseed meal costs $7.50, then six pounds of actual nitrogen from cottonseed meal costs 2 x $7.50 = $15.00.

Now, lets take a brief moment to see why industrial farmers thinking only of immediate financial profit, use chemical fertilizers. Urea, a synthetic form of urine used as nitrogen fertilizer contains 48 percent nitrogen. So 100 pounds of urea contains 48 pounds of nitrogen. That quant.i.ty of urea also costs about $15.00!

Without taking into account its value in terms of phosphorus, pota.s.sium and other mineral contents, nitrogen from seed meal costs at least eight times as much per pound as nitrogen from urea.

Newspapers, even with colored inks, can be safely used in compost piles. Though some colored inks do contain heavy metals, these are not used on newsprint.

However, before beginning to incorporate newsprint into your composting, reconsider the a.n.a.lyses of various types of compost broken out as a table in the previous chapter. The main reason many munic.i.p.al composting programs make a low-grade product with such a high C/N is the large proportion of paper used. If your compost is intended for use as mulch around perennial beds or to be screened and broadcast atop lawns, then having a nitrogen-poor product is of little consequence. But if your compost is headed for the vegetable garden or will be used to grow the largest possible prized flowers then perhaps newsprint could be recycled in another way.

Cardboard, especially corrugated material, is superior to newsprint for compost making because its biodegradable glues contain significant amounts of nitrogen. Worms love to consume cardboard mulch. Like other forms of paper, cardboard should be shredded, ground or chopped as finely as possible, and thoroughly mixed with other materials when composted._

__Pet wastes_ may contain disease organisms that infect humans.

Though munic.i.p.al composting systems can safely eliminate such diseases, home composting of dog and cat manure may be risky if the compost is intended for food gardening.

_Phosphate rock._ If your garden soil is deficient in phosphorus, adding rock phosphate to the compost pile may accelerate its availability in the garden, far more effectively than adding phosphate to soil. If the vegetation in your vicinity comes from soils similarly deficient in phosphorus, adding phosphate rock will support a healthier decomposition ecology and improve the quality of your compost. Five to ten pounds of rock phosphate added to a cubic yard of uncomposted organic matter is about the right amount.

_Rice hulls:_ See _Buckwheat hulls._

_Rock dust._ All plant nutrients except nitrogen originally come from decomposing rock. Not all rocks contain equal concentrations and a.s.sortments of the elements plants use for nutrients.

Consequently, not all soils l.u.s.tily grow healthy plants. One very natural way to improve the over all fertility of soil is to spread and till in finely ground rock flour make from highly mineralized rocks.

This method is not a new idea. Limestone and dolomite--soft, easily powdered rocks--have been used for centuries to add calcium and magnesium. For over a century, rock phosphate and kainite--a soft, readily soluble naturally occurring rock rich in pota.s.sium, magnesium and sulfur--have been ground and used as fertilizer. Other natural rock sources like Jersey greensand have long been used in the eastern United States on some unusual pota.s.sium-deficient soils.

Lately it has become fashionable to remineralize the earth with heavy applications of rock flours. Unlike most fads and trends, this one is wise and should endure. The best rocks to use are finely ground "basic" igneous rocks like basalts. They are called basic as opposed to "acid" rocks because they are richer in calcium and magnesium with lesser quant.i.ties of pota.s.sium. When soil forms from these materials it tends to not be acid. Most basic igneous rocks also contain a wide range of trace mineral nutrients. I have observed marked improvements in plant growth by incorporating ordinary basalt dust that I personally shoveled from below a conveyor belt roller at a local quarry where crushed rock was being prepared for road building. Basalt dust was an unintentional byproduct.

Though highly mineralized rock dust may be a valuable soil amendment, its value must equal its cost. Application rates of one or two tons per acre are minimal. John Hamaker's _The Survival of Civilization _suggests eight to ten tons per acre the first application and then one or two tons every few years thereafter.

This means the correct price for rock dust is similar to the price for agricultural lime; in my region that's about $60 to $80 a ton in sacks. Local farmers pay about $40 a ton in bulk, including spreading on your field by the seller. A fifty-pound sack of rock dust should retail for about $2. These days it probably costs several times that price, tending to keep rock dust a novelty item.

The activities of fungi and bacteria are the most potent forces making nutrients available to plants. As useful as tilling rock powders into soil may be, the intense biological activity of the compost pile accelerates their availability. And the presence of these minerals might well make a compost pile containing nutrient-deficient vegetation work faster and become better fertilizer. Were the right types of rock dust available and cheap, I'd make it about 5 percent by volume of my heap, and equal that with rich soil.

_Safflowerseed meal._ See _Cottonseed meal._

_Sawdust_ contains virtually nothing but carbon. In small quant.i.ties it is useful to fluff up compost piles and prevent compaction.

However this is only true of coa.r.s.e material like that from sawmills or chain saws. The fine saw dust from carpentry and cabinet work may compact and become airless. See _Paper _for a discussion of lowering the fertilizing value of compost with high C/N materials.

_Seaweed_ when freshly gathered is an extraordinary material for the compost pile. Like most living things from the ocean seaweeds are rich in all of the trace minerals and contain significant amounts of the major nutrients, especially pota.s.sium, with lesser amounts of phosphorus and nitrogen. Seaweeds enrich the heap, decompose very rapidly, and a.s.sist other materials to break down. Though heavy and often awkward to gather and haul, if they are available, seaweeds should not be permitted to go to waste.

Those with unlimited money may use sprinklings of kelp meal in the compost pile to get a similar effect. However, kelp meal may be more economically used as part of a complete organic fertilizer mixture that is worked into soil.

_Shrub and tree_ prunings are difficult materials to compost unless you have a shredder/chipper. Even after being incorporated into one hot compost heap after another, half-inch diameter twigs may take several years to fully decompose. And turning a heap containing long branches can be very difficult. But buying power equipment just to grind a few cart loads of hedge and tree prunings each year may not be economical. My suggestion is to neatly tie any stick larger than your little finger into tight bundles about one foot in diameter and about 16 inches long and then burn these "f.a.ggots" in the fireplace or wood stove. This will be less work in the long run.