Organic Gardener's Composting Part 9

Promotional materials make composting in pre-manufactured bins seem easy, self-righteously ecological, and effortless. However, there are drawbacks.

It is not possible to readily turn the materials once they've been placed into most composters of this type unless the entire front is removable. Instead, new materials are continuously placed on top while an opening at the bottom permits the gardener to sc.r.a.pe out finished compost in small quant.i.ties. Because no turning is involved, this method is called "pa.s.sive" composting. But to work well, the ingredients must not be too coa.r.s.e and must be well mixed before loading.

Continuous bin composters generally work fast enough when processing_ mixtures _of readily decomposable materials like kitchen garbage, weeds, gra.s.s clippings and some leaves. But if the load contains too much fine gra.s.s or other gooey stuff and goes anaerobic, a special compost aerator must be used to loosen it up.

Manufactured pa.s.sive composters are not very large. Compactness may be an advantage to people with very small yards or who may want to compost on their terrace or porch. But if the C/N of the materials is not favorable, decomposition can take a long, long time and several bins may have to be used in tandem. Unless they are first ground or chopped very finely, larger more resistant materials like corn, Brussels sprouts, sunflower stalks, cabbage stumps, shrub prunings, etc. will "constipate" a top-loading, bottom-discharging composter.

The compost tumbler is a clever method that accelerates decomposition by improving aeration and facilitating frequent turning. A rotating drum holding from eight to eighteen bushels (the larger sizes look like a squat, fat, oversized oil drum) is suspended above the ground, top-loaded with organic matter, and then tumbled every few days for a few weeks until the materials have decomposed. Then the door is opened and finished compost falls out the bottom.

Tumblers have real advantages. Frequent turning greatly increases air supply and accelerates the process. Most tumblers r.e.t.a.r.d moisture loss too because they are made of solid material, either heavy plastic or steel with small air vents. Being suspended above ground makes them immune to vermin and frequent turning makes it impossible for flies to breed.

Tumblers have disadvantages that may not become apparent until a person has used one for awhile. First, although greatly accelerated, composting in them is not instantaneous. Pa.s.sive bins are continuous processors while (with the exception of one unique design) tumblers are "batch" processors, meaning that they are first loaded and then the entire load is decomposed to finished compost. What does a person do with newly acquired kitchen garbage and other waste during the two to six weeks that they are tumbling a batch? One handy solution is to buy two tumblers and be filling one while the other is working, but tumblers aren't cheap! The more substantial ones cost $250 to $400 plus freight.

There are other less obvious tumbler disadvantages that may negate any work avoided, time saved, or sweaty turning with a manure fork eliminated. Being top-loaded means lifting compost materials and dropping them into a small opening that may be shoulder height or more. These materials may include a sloppy bucket of kitchen garbage. Then, a tumbler _must_ be tumbled for a few minutes every two or three days. Cranking the lever or grunting with the barrel may seem like fun at first but it can get old fast. Decomposition in an untumbled tumbler slows down to a crawl.

Both the pa.s.sive compost bin and the highly active compost tumbler work much better when loaded with small-sized particles. The purchase of either one tends to impel the gardener to also buy something to cut and/or grind compost materials.

The U.C. Method--Grinder/Shredders

During the 1950s, mainstream interest in munic.i.p.al composting developed in America for the first time. Various industrial processes already existed in Europe; most of these were patented variations on large and expensive composting tumblers. Researchers at the University of California set out to see if simpler methods could be developed to handle urban organic wastes without investing in so much heavy machinery. Their best system, named the U. C. Fast Compost Method, rapidly made compost in about two weeks.

No claim was ever made that U. C. method produces the highest quality compost. The idea was to process and decompose organic matter as inoffensively and rapidly as possible. No attempt is made to maximize the product's C/N as is done in slower methods developed by Howard at Indore. Most munic.i.p.al composting done in this country today follows the basic process worked out by the University of California.

Speed of decomposition comes about from very high internal heat and extreme aerobic conditions. To achieve the highest possible temperature, all of the organic material to be composted is first pa.s.sed through a grinder and then stacked in a long, high windrow.

Generally the height is about five to six feet, any higher causes too much compaction. Because the material is stacked with sides as vertical as possible, the width takes care of itself.

Frequent turning with machinery keeps the heap working rapidly.

During the initial experiments the turning was done with a tractor and front end loader. These days giant "U" shaped machines may roll down windrows at munic.i.p.al composting plots, automatically turning, reshaping the windrow and if necessary, simultaneously spraying water.

Some munic.i.p.al waste consists of moist kitchen garbage and gra.s.s clippings. Most of the rest is dry paper. If this mixture results in a moisture content that is too high the pile gets soggy, sags promptly, and easily goes anaerobic. Turning not only restores aerobic conditions, but also tends to drop the moisture content. If the initial moisture content is between 60 and 70 percent, the windrow is turned every two days. Five such turns, starting two days after the windrow is first formed, finishes the processing. If the moisture content is between 10 and 60 percent, the windrow is first turned after three days and thence at three day intervals, taking about four turns to finish the process. If the moisture content is below 40 percent or drops below 40 percent during processing, moisture is added.

No nuisances can develop if turning is done correctly. Simply flipping the heap over or adding new material on top will not do it.

The material must be blended so that the outsides are shifted to the core and the core becomes the skin. This way, any fly larvae, pathogens, or insect eggs that might not be killed by the cooler temperatures on the outside are rotated into the lethal high heat of the core every few days.

The speed of the U.C. method also appeals to the backyard gardener.

At home, frequent turning can be accomplished either in naked heaps, or by switching from one bin to the next and back, or with a compost tumbler. But a chipper/shredder is also essential. Grinding everything that goes into the heap has other advantages than higher heat and accelerated processing. Materials may be initially mixed as they are ground and small particles are much easier to turn over than long twigs, tough straw, and other fibrous materials that tie the heap together and make it difficult to separate and handle with hand tools.

Backyard shredders have other uses, especially for gardeners with no land to waste. Composting tough materials like grape prunings, berry canes, and hedge tr.i.m.m.i.n.gs can take a long time. Slow heaps containing resistant materials occupy precious s.p.a.ce. With a shredder you can fast-compost small limbs, tree prunings, and other woody materials like corn and sunflower stalks. Whole autumn leaves tend to compact into airless layers and decompose slowly, but dry leaves are among the easiest of all materials to grind. Once smashed into flakes, leaves become a fluffy material that resists compaction.

Electric driven garden chipper/shredders are easier on the neighbors' ears than more powerful gasoline-powered machines, although not so quiet that I'd run one without ear protection.

Electrics are light enough for a strong person to pick up and carry out to the composting area and keep secured in a storeroom. One more plus, there never is any problem starting an electric motor. But no way to conveniently repair one either.

There are two basic shredding systems. One is the hammermill--a grinding chamber containing a rotating spindle with steel tines or hammers attached that repeatedly beats and tears materials into smaller and smaller pieces until they fall out through a bottom screen. Hammermills will flail almost anything to pieces without becoming dulled. Soft, green materials are beaten to shreds; hard, dry, brittle stuff is rapidly fractured into tiny chips. Changing the size of the discharge screen adjusts the size of the final product. By using very coa.r.s.e screens, even soft, wet, stringy materials can be slowly fed through the grinding chamber without hopelessly tangling up in the hammers.

Like a coa.r.s.e power planer in a wood shop, the other type of machine uses sharpened blades that slice thin chips from whatever is pushed into its maw. The chipper is designed to grind woody materials like small tree limbs, prunings, and berry canes. Proper functioning depends on having sharp blades. But edges easily become dulled and require maintenance. Care must be taken to avoid pa.s.sing soil and small stones through a chipper. Soft, dry, brittle materials like leaves will be broken up but aren't processed as rapidly as in a hammermill. Chippers won't handle soft wet stuff.

When driven by low horsepower electric motors, both chippers and hammermills are light-duty machines. They may be a little shaky, standing on spindly legs or small platforms, so materials must be fed in gently. Most electric models cost between $300 and $400.

People with more than a postage-stamp yard who like dealing with machinery may want a gasoline-powered shredder/chipper. These are much more substantial machines that combine both a big hammermill shredder with a side-feeding chipper for limbs and branches.

Flailing within a hammermill or chipping limbs of two or more inches in diameter focuses a great deal of force; between the engine noise and the deafening din as dry materials bang around the grinding chamber, ear protection is essential. So are safety goggles and heavy gloves. Even though the fan belt driving the spindle is shielded, I would not operate one without wearing tight-fitting clothes. When grinding dry materials, great clouds of dust may be given off. Some of these particles, like the dust from alfalfa or from dried-out spoiled (moldy) hay, can severely irritate lungs, eyes, throat and nasal pa.s.sages. A face mask, or better, an army surplus gas mask with built-in goggles, may be in order. And you'll probably want to take a shower when finished.

Fitted with the right-size screen selected from the a.s.sortment supplied at purchase, something learned after a bit of experience, powerful hammermills are capable of pulverizing fairly large amounts of dry material in short order. But wet stuff is much slower to pa.s.s through and may take a much coa.r.s.er screen to get out at all.

Changing materials may mean changing screens and that takes a few minutes. Dry leaves seem to flow through as fast as they can be fed in. The side-feed auxiliary chippers incorporated into hammermills will make short work of smaller green tree limbs; but dry, hardened wood takes a lot longer. Feeding large hard branches too fast can tear up chipper blades and even break the ball-bearing housings holding the spindle. Here I speak from experience.

Though advertis.e.m.e.nts for these machines make them seem effortless and fast, shredders actually take considerable time, energy, skilled attention, constant concentration, and experience. When grinding one must attentively match the inflow to the rate of outflow because if the hopper is overfilled the tines become snarled and cease to work.

For example, tangling easily can occur while rapidly feeding in thin brittle flakes of dry spoiled hay and then failing to slow down while a soft, wet flake is gradually reduced. To clear a snarled rotor without risking continued attachment of one's own arm, the motor must be killed before reaching into the hopper and untangling the tines. To clear badly clogged machines it may also be necessary to first remove and then replace the discharge screen, something that takes a few minutes.

There are significant differences in the quality of materials and workmanship that go into making these machines. They all look good when freshly painted; it is not always possible to know what you have bought until a season or two of heavy use has pa.s.sed. One tried-and-true aid to choosing quality is to ask equipment rental businesses what brand their customers are not able to destroy.

Another guide is to observe the brand of gasoline engine attached.

In my gardening career I've owned quite a few gas-powered rotary tillers and lawnmowers and one eight-horsepower shredder. In my experience there are two grades of small gasoline engines--"consumer" and the genuine "industrial." Like all consumer merchandise, consumer-grade engines are intended to be consumed.

They have a design life of a few hundred hours and then are worn out. Most parts are made of soft, easily-machined aluminum, reinforced with small amounts of steel in vital places.

There are two genuinely superior American companies--Kohler and Wisconsin-that make very durable, long-lasting gas engines commonly found on small industrial equipment. With proper maintenance their machines are designed to endure thousands of hours of continuous use. I believe small gas engines made by Yamaha, Kawasaki, and especially Honda, are of equal or greater quality to anything made in America. I suggest you could do worse than to judge how long the maker expects their shredder/chipper to last by the motor it selects.

Gasoline-powered shredder/chippers cost from $700 to $1,300. Back in the early 1970s I wore one pretty well out in only one year of making fast compost for a half-acre Biodynamic French intensive market garden. When I amortized the cost of the machine into the value of both the compost and the vegetables I grew with the compost, and considered the amount of time I spent running the grinder against the extra energy it takes to turn ordinary slow compost heaps I decided I would be better off allowing my heaps to take more time to mature.

Sheet Composting

Decomposition happens rapidly in a hot compost heap with the main agents of decay being heat-loving microorganisms. Decomposition happens slowly at the soil's surface with the main agents of decay being soil animals. However, if the leaves and forest duff on the floor of a forest or a thick matted sod are tilled into the topsoil, decomposition is greatly accelerated.

For two centuries, frontier American agriculture depended on just such a method. Early pioneers would move into an untouched region, clear the forest, and plow in millennia of acc.u.mulated nutrients held as bioma.s.s on the forest floor. For a few years, perhaps a decade, or even twenty years if the soil carried a higher level of mineralization than the average, crops from forest soils grew magnificently. Then, unless other methods were introduced to rebuild fertility, yields, crop, animal, and human health all declined. When the less-leached gra.s.sy prairies of what we now call the Midwest were reached, even greater bounties were mined out for more years because rich black-soil gra.s.slands contain more mineral nutrients and sod acc.u.mulates far more humus than do forests.

Sheet composting mimics this system while saving a great deal of effort. Instead of first heaping organic matter up, turning it several times, carting humus back to the garden, spreading it, and tilling it in, sheet composting conducts the decomposition process with far less effort right in the soil needing enrichment.

Sheet composting is the easiest method of all. However, the method has certain liabilities. Unless the material being spread is pure manure without significant amounts of bedding, or only fresh spring gra.s.s clippings, or alfalfa hay, the carbon-nitrogen ratio will almost certainly be well above that of stable humus. As explained earlier, during the initial stages of decay the soil will be thoroughly depleted of nutrients. Only after the surplus carbon has been consumed will the soil ecology and nutrient profile normalize.

The time this will take depends on the nature of the materials being composted and on soil conditions.

If the soil is moist, airy, and warm and if it already contained high levels of nutrients, and if the organic materials are not ligninous and tough and have a reasonable C/N, then sheet composting will proceed rapidly. If the soil is cold, dry, clayey (relatively airless) or infertile and/or the organic matter consists of things like grain straw, paper, or the very worst, barkless sawdust, then decomposition will be slowed. Obviously, it is not possible to state with any precision how fast sheet composting would proceed for you.

Autumn leaves usually sheet compost very successfully. These are gathered, spread over all of the garden (except for those areas intended for early spring sowing), and tilled in as shallowly as possible before winter. Even in the North where soil freezes solid for months, some decomposition will occur in autumn and then in spring, as the soil warms, composting instantly resumes and is finished by the time frost danger is over. Sheet composting higher C/N materials in spring is also workable where the land is not scheduled for planting early. If the organic matter has a low C/N, like manure, a tender green manure crop not yet forming seed, alfalfa hay or gra.s.s clippings, quite a large volume of material can be decomposed by warm soil in a matter of weeks.

However, rotting large quant.i.ties of very resistant material like sawdust can take many months, even in hot, moist soil. Most gardeners cannot afford to give their valuable land over to being a compost factory for months. One way to speed the sheet composting of something with a high C/N is to amend it with a strong nitrogen source like chicken manure or seed meal. If sawdust is the only organic matter you can find, I recommend an exception to avoiding chemical fertilizer. By adding about 80 pounds of urea to each cubic yard of sawdust, its overall C/N is reduced from 500:1 to about 20:1. Urea is perhaps the most benign of all chemical nitrogen sources. It does not acidify the soil, is not toxic to worms or other soil animals or microorganisms, and is actually a synthetic form of the naturally occurring chemical that contains most of the nitrogen in animal urine. In that sense, putting urea in soil is not that different than putting synthetic vitamin C in a human body

Burying kitchen garbage is a traditional form of sheet composting practiced by row-cropping gardeners usually in mild climates where the soil does not freeze in winter. Some people use a post hole digger to make a neat six-to eight-inch diameter hole about eighteen inches deep between well-s.p.a.ced growing rows of plants. When the hole has been filled to within two or three inches of the surface, it is topped off with soil. Rarely will animals molest buried garbage, it is safe from flies and yet enough air exists in the soil for it to rapidly decompose. The local soil ecology and nutrient balance is temporarily disrupted, but the upset only happens in this one little spot far enough away from growing plants to have no harmful effect.

Another garbage disposal variation has been called "trench composting." Instead of a post hole, a long trench about the width of a combination shovel and a foot deep is gradually dug between row crops s.p.a.ced about four feet (or more) apart. As bucket after bucket of garbage, manure, and other organic matter are emptied into the trench, it is covered with soil dug from a little further along.

Next year, the rows are shifted two feet over so that crops are sown above the composted garbage.

Mulch Gardening

Ruth Stout discovered--or at least popularized this new-to-her method. Mulching may owe some of its popularity to Ruth's possession of writing talent similar to her brother Rex's, who was a well-known mid-century mystery writer. Ruth's humorous book, _Gardening Without Work_ is a fun-to-read cla.s.sic that I highly recommend if for no other reason than it shows how an intelligent person can make remarkable discoveries simply by observing the obvious. However, like many other garden writers, Ruth Stout made the mistake of a.s.suming that what worked in her own backyard would be universally applicable. Mulch gardening does not succeed everywhere.

This easy method mimics decomposition on the forest floor. Instead of making compost heaps or sheet composting, the garden is kept thickly covered with a permanent layer of decomposing vegetation.

Year-round mulch produces a number of synergistic advantages. Decay on the soil's surface is slow but steady and maintains fertility. As on the forest floor, soil animals and worm populations are high.

Their activities continuously loosen the earth, steadily transport humus and nutrients deeper into the soil, and eliminate all need for tillage. Protected from the sun, the surface layers of soil do not dry out so shallow-feeding species like lettuce and moisture-lovers like radishes make much better growth. During high summer, mulched ground does not become unhealthfully heated up either.

The advantages go on. The very top layer of soil directly under the mulch has a high organic matter content, retaining moisture, eliminating crusting, and consequently, enhancing the germination of seeds. Mulchers usually sow in well-separated rows. The gardener merely rakes back the mulch and exposes a few inches of bare soil, scratches a furrow, and covers the seed with humusy topsoil. As the seedlings grow taller and are thinned out, the mulch is gradually pushed back around them.