Organic matter that has been in soil for a while has been altered into a much studied substance, humus. We know for example that humus always has a carbon to nitrogen ratio of from 10:1 to about 12:1, just like compost from Garden "B." Garden writers call great compost like this, "stable humus," because it is slow to decompose. Its presence in soil steadily feeds a healthy ecology of microorganisms important to plant health, and whose activity accelerates release of plant nutrients from undecomposed rock particles. Humus is also fertilizer because its gradual decomposition provides mineral nutrients that make plants grow. The most important of these nutrients is nitrate nitrogen, thus soil scientists may call humus decomposition "nitrification."

When organic material with a C/N below 12:1 is mixed into soil its breakdown is very rapid. Because it contains more nitrogen than stable humus does, nitrogen is rapidly released to feed the plants and soil life. Along with nitrogen comes other plant nutrients. This accelerated nitrification continues until the remaining nitrogen balances with the remaining carbon at a ratio of about 12:1. Then the soil returns to equilibrium. The lower the C/N the more rapid the release, and the more violent the reaction in the soil. Most low C/N organic materials, like seed meal or chicken manure, rapidly release nutrients for a month or two before stabilizing. What has been described here is fertilizer.

When organic material with a C/N higher than 12:1 is tilled into soil, soil animals and microorganisms find themselves with an unsurpa.s.sed carbohydrate banquet. Just as in a compost heap, within days bacteria and fungi can multiply to match any food supply. But to construct their bodies these microorganisms need the same nutrients that plants need to grow--nitrogen, pota.s.sium, phosphorus, calcium, magnesium, etc. There are never enough of these nutrients in high C/N organic matter to match the needs of soil bacteria, especially never enough nitrogen, so soil microorganisms uptake these nutrients from the soil's reserves while they "bloom" and rapidly consume all the new carbon presented to them.

During this period of rapid decomposition the soil is thoroughly robbed of plant nutrients. And nitrification stops. Initially, a great deal of carbon dioxide gas may be given off, as carbon is metabolically "burned." However, CO2 in high concentrations can be toxic to sprouting seeds and consequently, germination failures may occur. When I was in the seed business I'd get a few complaints every year from irate gardeners demanding to know why every seed packet they sowed failed to come up well. There were two usual causes. Either before sowing all the seeds were exposed to temperatures above 110 degree or more likely, a large quant.i.ty of high C/N "manure" was tilled into the garden just before sowing. In soil so disturbed transplants may also fail to grow for awhile. If the "manure" contains a large quant.i.ty of sawdust the soil will seem very infertile for a month or three.

Sir Albert Howard had a unique and pithy way of expressing this reality. He said that soil was not capable of working two jobs at once. You could not expect it to nitrify humus while it was also being required to digest organic matter. That's one reason he thought composting was such a valuable process. The digestion of organic matter proceeds outside the soil; when finished product, humus, is ready for nitrification, it is tilled in.

Rapid consumption of carbon continues until the C/N of the new material drops to the range of stable humus. Then decay microorganisms die off and the nutrients they h.o.a.rded are released back into the soil. How long the soil remains inhospitable to plant growth and seed germination depends on soil temperature, the amount of the material and how high its C/N is, and the amount of nutrients the soil is holding in reserve. The warmer and more fertile the soil was before the addition of high C/N organic matter, the faster it will decompose.

Judging by the compost a.n.a.lyses in the table, I can see why some munic.i.p.alities are having difficulty disposing of the solid waste compost they are making. One governmental composting operation that does succeed in selling everything they can produce is Lane County, Oregon. Their _yard waste compost_ is eagerly paid for by local gardeners. Lane County compost is made only from autumn leaves, gra.s.s clippings, and other yard wastes. No paper!

Yard waste compost is a product much like a homeowner would produce.

And yard waste compost contains no industrial waste or any material that might pose health threats. All woody materials are finely chipped before composting and comprise no more than 20 percent of the total undecayed ma.s.s by weight. Although no nutrient a.n.a.lysis has been done by the county other than testing for pH (around 7.0) and, because of the use of weed and feed fertilizers on lawns, for 2-4D (no residual trace ever found present), I estimate that the overall C/N of the materials going into the windrows at 25:1. I wouldn't be surprised if the finished compost has a C/N close to 12:1.

Incidentally, Lane County understands that many gardeners don't have pickup trucks. They reasonably offer to deliver their compost for a small fee if at least one yard is purchased. Other local governments also make and deliver yard waste compost.

So what about your own home compost? If you are a flower, ornamental, or lawn grower, you have nothing to worry about. Just compost everything you have available and use all you wish to make.

If tilling your compost into soil seems to slow the growth of plants, then mulch with it and avoid tilling it in, or adjust the C/N down by adding fertilizers like seed meal when tilling it in.

If you are a vegetable gardener and your compost doesn't seem to provoke the kind of growth response you hoped for, either shallowly till in compost in the fall for next year's planting, by which time it will have become stable humus, or read further. The second half of this book contains numerous hints about how to make potent compost and about how to use complete organic fertilizers in combination with compost to grow the lushest garden imaginable.

CHAPTER FOUR

All About Materials

In most parts of the country, enough organic materials acc.u.mulate around an average home and yard to make all the compost a backyard garden needs. You probably have weeds, leaves, perhaps your own human hair (my wife is the family barber), dust from the vacuum cleaner, kitchen garbage and gra.s.s clippings. But, there may not be enough to simultaneously build the lushest lawn, the healthiest ornamentals _and _grow the vegetables. If you want to make more compost than your own land allows, it is not difficult to find very large quant.i.ties of organic materials that are free or cost very little.

The most obvious material to bring in for composting is animal manure. Chicken and egg raisers and boarding stables often give manure away or sell it for a nominal fee. For a few dollars most small scale animal growers will cheerfully use their scoop loader to fill your pickup truck till the springs sag.

As useful as animal manure can be in a compost pile, there are other types of low C/N materials too. Enormous quant.i.ties of loose alfalfa acc.u.mulate around hay bale stacks at feed and grain stores. To the proprietor this dusty chaff is a nuisance gladly given to anyone that will neatly sweep it up and truck it away. To the home gardener, alfalfa in any form is rich as gold.

Some years, rainy Oregon weather is still unsettled at haying season and farmers are stuck with spoiled hay. I'm sure this happens most places that gra.s.s hay is grown on natural rainfall. Though a shrewd farmer may try to sell moldy hay at a steep discount by representing it to still have feed value, actually these ruined bales must be removed from a field before they interfere with working the land. A hard bargainer can often get spoiled hay in exchange for hauling the wet bales out of the field

There's one local farmer near me whose entire family tree holds a well-deserved reputation for hard, self-interested dealing. One particularly wet, cool unsettled haying season, after starting the spoiled-hay d.i.c.ker at 90 cents per bale asked--nothing offered but hauling the soggy bales out of the field my offer--I finally agreed to take away about twenty tons at ten cents per bale. This small sum allowed the greedy b-----to feel he had gotten the better of me. He needed that feeling far more than I needed to win the argument or to keep the few dollars Besides, the workings of self-applied justice that some religious philosophers call karma show that over the long haul the worst thing one person can do to another is to allow the other to get away with an evil act.

Any dedicated composter can make contacts yielding cheap or free organic materials by the ton. Orchards may have badly bruised or rotting fruit. Small cider mills, wineries, or a local juice bar restaurant may be glad to get rid of pomace. Carpentry shops have sawdust. Coffee roasters have dust and chaff. The microbrewery is becoming very popular these days; mall-scale local brewers and distillers may have spent hops and mash. Spoiled product or chaff may be available from cereal mills.

City governments often will deliver autumn leaves by the ton and will give away or sell the output of their own munic.i.p.al composting operations. Supermarkets, produce wholesalers, and restaurants may be willing to give away boxes of tr.i.m.m.i.n.gs and spoiled food. Barbers and poodle groomers throw away hair.

Seafood processors will sell truckloads of fresh crab, fish and shrimp waste for a small fee. Of course, this material becomes evil-smelling in very short order but might be relatively inoffensive if a person had a lot of spoiled hay or sawdust waiting to mix into it. Market gardeners near the Oregon coast sheet-compost crab waste, tilling it into the soil before it gets too "high."

Other parts of the country might supply citrus wastes, sugar cane baga.s.se, rice hulls, etc.

About Common Materials

_Alfalfa_ is a protein-rich perennial legume mainly grown as animal feed. On favorable soil it develops a deep root system, sometimes exceeding ten feet. Alfalfa draws heavily on subsoil minerals so it will be as rich or poor in nutrients as the subsoil it grew in. Its average C/N is around 12:1 making alfalfa useful to compensate for larger quant.i.ties of less potent material. Sacked alfalfa meal or pellets are usually less expensive (and being "stemmy," have a slightly higher C/N) than leafy, best-quality baled alfalfa hay.

Rain-spoiled bales of alfalfa hay are worthless as animal feed but far from valueless to the composter.

Pelletized rabbit feed is largely alfalfa fortified with grain.

Naturally, rabbit manure has a C/N very similar to alfalfa and is nutrient rich, especially if some provision is made to absorb the urine.

_Apple pomace_ is wet and compact. If not well mixed with stiff, absorbent material, large clumps of this or other fruit wastes can become airless regions of anaerobic decomposition. Having a high water content can be looked upon as an advantage. Dry hay and sawdust can be hard to moisten thoroughly; these hydrate rapidly when mixed with fruit pulp. Fermenting fruit pulp attracts yellow jackets so it is sensible to incorporate it quickly into a pile and cover well with vegetation or soil.

The watery pulp of fruits is not particularly rich in nutrients but apple, grape, and pear pulps are generously endowed with soft, decomposable seeds. Most seeds contain large quant.i.ties of phosphorus, nitrogen, and other plant nutrients. It is generally true that plants locate much of their entire yearly nutrient a.s.similation into their seeds to provide the next generation with the best possible start. Animals fed on seeds (such as chickens) produce the richest manures.

Older books about composting warn about metallic pesticide residues adhering to fruit skins. However, it has been nearly half a century since a.r.s.enic and lead a.r.s.enate were used as pesticides and mercury is no longer used in fungicides.

_Baga.s.se_ is the voluminous waste product from extracting cane sugar. Its C/N is extremely high, similar to wheat straw or sawdust, and it contains very little in the way of plant nutrients. However, its coa.r.s.e, strong, fibrous structure helps build lightness into a pile and improve air flow. Most sugar mills burn baga.s.se as their heat source to evaporate water out of the sugary juice squeezed from the canes. At one time there was far more baga.s.se produced than the mills needed to burn and baga.s.se often became an environmental pollutant. Then, baga.s.se was available for nothing or next to nothing. These days, larger, modern mills generate electricity with baga.s.se and sell their surplus to the local power grid. Baga.s.se is also used to make construction fiberboard for subwall and insulation.

_Banana skins _and stalks are soft and lack strong fiber. They are moderately rich in phosphorus, pota.s.sium, and nitrogen. Consequently they rot quickly. Like other kitchen garbage, banana waste should be put into the core of a compost pile to avoid attracting and breeding flies. See also: _Garbage._

_Basic slag_ is an industrial waste from smelting iron. Ore is refined by heating it with limestone and dolomite. The impurities combine with calcium and magnesium, rise to the surface of the molten metal, and are skimmed off. Basic slag contains quite a bit of calcium plus a variety of useful plant nutrients not usually found in limestone. Its exact composition varies greatly depending on the type of ore used.

Slag is pulverized and sold in sacks as a subst.i.tute for agricultural lime. The intense biological activity of a compost pile releases more of slag's other mineral content and converts its nutrients to organic substances that become rapidly available once the compost is incorporated into soil. Other forms of powdered mineralized rock can be similarly added to a compost pile to accelerate nutrient release.

Rodale Press, publisher of _Organic Gardening_ magazine is located in Pennsylvania where steel mills abound. Having more experience with slag, Rodale advises the user to be alert to the fact that some contain little in the way of useful nutrients and/or may contain excessive amounts of sulfur. Large quant.i.ties of sulfur can acidify soil. Read the a.n.a.lysis on the label. Agriculturally useful slag has an average composition of 40 percent calcium and 5 percent magnesium. It must also be very finely ground to be effective. See also: _Lime_ and _Rock dust._

_Beet wastes,_ like baga.s.se, are a residue of extracting sugar. They have commercial value as livestock feed and are sold as dry pulp in feed stores located near regions where sugar beets are grown. Their C/N is in the vicinity of 20:1 and they may contain high levels of pota.s.sium, reaching as much as 4 percent.

_Brewery wastes._ Both spent hops (dried flowers and leaves) and malt (sprouted barley and often other grains) are potent nutrient sources with low C/N ratios. Spent malt is especially potent because brewers extract all the starches and convert them to sugar, but consider the proteins as waste because proteins in the brew make it cloudy and opaque. Hops may be easier to get. Malt has uses as animal feed and may be contracted for by some local feedlot or farmer. These materials will be wet, heavy and frutily odoriferous (though not unpleasantly so) and you will want to incorporate them into your compost pile immediately.

_Buckwheat hulls._ Buckwheat is a grain grown in the northeastern United States and Canada. Adapted to poor, droughty soils, the crop is often grown as a green manure. The seeds are enclosed in a thin-walled, brown to black fibrous hulls that are removed at a groat mill. Buckwheat hulls are light, springy, and airy. They'll help fluff up a compost heap. Buckwheat hulls are popular as a mulch because they adsorb moisture easily, look attractive, and stay in place. Their C/N is high. Oat and rice hulls are similar products.

_Canola meal._ See: _Cottonseed meal._

_Castor pomace_ is pulp left after castor oil has been squeezed from castor bean seeds. Like other oil seed residues it is very high in nitrogen, rich in other plant nutrients, particularly phosphorus, Castor pomace may be available in the deep South; it makes a fine subst.i.tute for animal manure.

_Citrus wastes_ may be available to gardeners living near industrial processors of orange, lemon, and grapefruit. In those regions, dried citrus pulp may also be available in feed stores. Dried orange skins contain about 3 percent phosphorus and 27 percent pota.s.sium. Lemons are a little higher in phosphorus but lower in pota.s.sium. Fruit culls would have a similar nutrient ratio on a dry weight basis, but they are largely water. Large quant.i.ties of culls could be useful to hydrate stubbornly dry materials like straw or sawdust.

Like other byproducts of industrial farming, citrus wastes may contain significant amounts of pesticide residues. The composting process will break down and eliminate most toxic organic residues, especially if the pile gets really hot through and through. (See also: _Leaves) _The effect of such high levels of pota.s.sium on the nutritional qualities of my food would also concern me if the compost I was making from these wastes were used for vegetable gardening.

_Coffee grounds_ are nutrient-rich like other seed meals. Even after brewing they can contain up to 2 percent nitrogen, about 1/2 percent phosphorus and varying amounts of pota.s.sium usually well below 1 percent. Its C/N runs around 12:1. Coffee roasters and packers need to dispose of coffee chaff, similar in nutrient value to used grounds and may occasionally have a load of overly roasted beans.

Coffee grounds seem the earthworm's food of choice. In worm bins, used grounds are more vigorously devoured than any other substance.

If slight odor is a consideration, especially if doing in-the-home vermicomposting, coffee grounds should be incorporated promptly into a pile to avoid the souring that results from vinegar-producing bacteria. Fermenting grounds may also attract harmless fruit flies.

Paper filters used to make drip coffee may be put into the heap or worm box where they contribute to the bedding. See also: _Paper._

_Corncobs_ are no longer available as an agricultural waste product because modern harvesting equipment shreds them and spits the residue right back into the field. However, home gardeners who fancy sweet corn may produce large quant.i.ties of cobs. Whole cobs will aerate compost heaps but are slow to decompose. If you want your pile ready within one year, it is better to dry and then grind the cobs before composting them.