Soil is an often overlooked but critically important part of the compost pile. Least of its numerous benefits, soil contains infinitudes of microorganisms that help start out decomposition.

Many compostable materials come with bits of soil already attached and few are sterile in themselves. But extra soil ensures that there will initially be a sufficient number and variety of these valuable organisms. Soil also contains insoluble minerals that are made soluble by biological activity. Some of these minerals may be in short supply in the organic matter itself and their addition may improve the health and vigor of the whole decomposition ecology. A generous addition of rock dust may do this even better.

Most important, soil contains nitrification microorganisms that readily convert ammonia gas to nitrates, and clay that will catch and temporarily hold ammonia. Nitrifying bacteria do not live outside of soil. Finally, a several inch thick layer of soil capping the heap serves as an extra insulator, holding in heat, raising the core temperature and helping seal in moisture. Making a compost heap as much as 10 percent soil by dry weight is the right target

Try thinking of soil somewhat like the moderators in an atomic reactor, controlling the reaction by trapping neutrons. Soil won't change the C/N of a heap but not being subject to significant breakdown it will slightly lower the maximum temperature of decomposition; while trapping ammonia emissions; and creating better conditions for nitrogen fixing bacteria to improve the C/N as the heap cools and ripens.

_Soybean meal._ See _Cottonseed meal._

_Straw_ is a carboniferous material similar to sawdust but usually contains more nutrients. It is a valuable aerator, each stalk acting as a tube for air to enter and move through the pile. Large quant.i.ties of long straw can make it very difficult to turn a heap the first time. I'd much prefer to have manure mixed with straw than with sawdust.

_Sunflowerseed meal._ See _Cottonseed meal._

_Tankage_ is another slaughterhouse or rendering plant waste consisting of all animal refuse except blood and fat. Locally it is called meat meal. See _Hoof and horn meal._

_Tofu factory waste._ Okara is the pulp left after soy milk has been squeezed from cooked, ground soybeans. Small-scale tofu makers will have many gallons of okara to dispose of each day. It makes good pig food so there may be compet.i.tion to obtain it. Like any other seed waste, okara is high in nitrogen and will be wet and readily putrefiable like brewery waste. Mix into compost piles immediately.

_Urine._ See _Manure._

_Weeds. _Their nutrient content is highly variable depending on the species and age of the plant. Weeds gone to seed are both low in nitrogen and require locating in the center of a hot heap to kill off the seeds. Tender young weeds are as rich in nitrogen as spring gra.s.s.

Weeds that propagate through underground stems or rhizomes like quack-gra.s.s, Johnsongra.s.s, bittersweet, and the like are better burnt.

_Wood ash_ from hardwoods is rich in pota.s.sium and contains significant amounts of calcium and other minerals. Ash from conifers may be similarly rich in pota.s.sium but contains little else. Wood ashes spread on the ground tend to lose their nutrients rapidly through leaching. If these nutrients are needed in your soil, then add the ash to your compost piles where it will become an unreachable part of the bioma.s.s that will be gradually released in the garden when the compost is used.

_Wood chips _are slow to decompose although they may be added to the compost pile if one is not in a hurry. Their chunkiness and stiff mechanical properties help aerate a heap. They are somewhat more nutrient rich than sawdust.

_Wool wastes_ are also called shoddy. _See Hair._

CHAPTER FIVE

Methods and Variations

_A note to the internet reader: In the the print-on-paper edition, this chapter and the next one on vermicomposting are full of ill.u.s.trations showing composting structures and accessories. These do not reproduce well on-line and are not included._

Growing the majority of my family's food absorbs all of the energy I care to put into gardening. So my yard is neat but s.h.a.ggy. Motivated by what I consider total rationality, my lawn is cut only when it threatens to overwhelm the lawnmower, and the lawn is not irrigated, so it browns off and stops growing in summer.

I don't grow flowers because I live on a river in a beautiful countryside setting surrounded by low mountains. Nothing I created could begin to compete with what nature freely offers my eye. One untidy bed of ornamentals by the front door are my bow to conventionality, but these fit the entrances northeast aspect by being Oregon woods natives like ferns, salal, Oregon grape and an almost wild rhododendron--all these species thrive without irrigation.

When I give lectures, I am confronted by the amazing gardening variations that humans are capable of. Some folks' raised vegetable beds are crude low mounds. Then, I am shown photographs of squared, paralleled vertical-walled raised beds, uniformly wrapped in cedar planks. Some gardens are planted in fairly straight rows, some are laid-out in carefully calculated interplanted hexagonal successions and some are a wild scattering of catch-as-catch-can. Some people don't eat many kinds of vegetables yet grow large stands of corn and beans for canning or freezing.

Others grow small patches of a great many species, creating a year-round gourmet produce stand for their personal enjoyment. Some gardeners grow English-style floral displays occupying every square inch of their yards and offering a constant succession of color and texture.

This chapter presents some of the many different ways people handle the disposal of yard and kitchen wastes. Compost making, like gardening, reflects variations in temperament. You probably weren't surprised at my casual landscaping because you already read about my unkempt compost heap. So I am similarly not surprised to discover backyard composting methods as neat as a German village, as aesthetic as a j.a.panese garden, as scientific as an engineer would design and as ugly as ...

Containers and Other Similar Methods

In my days of youthful indiscretions I thought I could improve life on Earth by civilizing high school youth through engendering in them an understanding of history. I confess I almost completely failed and gave up teaching after a few years. However, I personally learned a great deal about history and the telling of history. I read many old journals, diaries, and travel accounts. From some of these doc.u.ments I gained little while other accounts introduced me to unique individuals who a.s.sisted me in understanding their era.

It seems that what differentiates good from bad reporting is how frank and honest the reporter is about their own personal opinions, prejudices, and outlooks. The more open and direct the reporter, the better the reader can discount inevitable distortions and get a picture of what might really have been there. The more the reporter attempts to be "objective" by hiding their viewpoints, the less valuable their information.

That is why before discussing those manufactured aids to composting that can make a consumer of you, I want to inform you that I am a frugal person who shuns unnecessary expenditure. I maintain what seems to me to be a perfect justification for my stinginess: I prefer relative unemployment. Whenever I want to buy something it has become my habit first to ask myself if the desired object could possibly bring me as much pleasure as knowing that I don't have to get up and go to work the next morning. Usually I decide to save the money so I do not have to earn more. _En extremis,_ I repeat the old Yankee marching chant like a mantra: Make do! Wear it out! When it is gone, do without! b.u.m, b.u.m! b.u.m bi Dum! b.u.m bi di Dum, b.u.m bi Dum!

So I do not own a shredder/grinder when patience will take its place. I do not buy or make composting containers when a country life style and not conforming to the neatness standards of others makes bins or tumblers unnecessary. However, I do grudgingly accept that others live differently. Let me warn you that my descriptions of composting aids and accessories are probably a little jaundiced.

I am doing my best to be fair.

Visual appeal is the primary benefit of making compost in a container. To a tidy, northern European sense of order, any composting structure will be far neater than the raw beauty of a naked heap. Composting container designs may offer additional advantages but no single structure will do everything possible. With an enclosure, it may be possible to heat up a pile smaller than 1' x 4' x 4' because the walls and sometimes the top of the container may be insulating. This is a great advantage to someone with a postage stamp backyard that treasures every square foot. Similarly, wrapping the heap r.e.t.a.r.ds moisture loss. Some structures shut out vermin.

On the other hand, structures can make it more difficult to make compost. Using a prefabricated bin can prevent a person from readily turning the heap and can almost force a person to also buy some sort of shredder/chipper to first reduce the size of the material. Also, viewed as a depreciating economic a.s.set with a limited life span, many composting aids cost as much or more money as the value of all the material they can ever turn out. Financial cost relates to ecological cost, so spending money on short-lived plastic or easily rusted metal may negate any environmental benefit gained from recycling yard wastes.

Building Your Own Bin

Probably the best homemade composting design is the multiple bin system where separate compartments facilitate continuous decomposition. Each bin is about four feet on a side and three to four feet tall. Usually, the dividing walls between bins are shared.

Always, each bin opens completely at the front. I think the best design has removable slatted separators between a series of four (not three) wooden bins in three declining sizes: two large, one medium-large and one smaller. Alternatively, bins may be constructed of unmortared concrete blocks with removable wooden fronts.

Permanently constructed bins of mortared concrete block or wood may have moisture-retentive, rain-protective hinged lids.

There are two workable composting systems that fit these structures.

Most composters obtain materials too gradually to make a large heap all at once. In this case my suggestion is the four-bin system, using one large bin as a storage area for dry vegetation. Begin composting in bin two by mixing the dry contents temporarily stored in bin one with kitchen garbage, gra.s.s clippings and etc. Once bin two is filled and heating, remove its front slats and the side slats separating it from bin three and turn the pile into bin three, gradually reinserting side slats as bin three is filled. Bin three, being about two-thirds the size of bin two, will be filled to the brim. A new pile can be forming in bin two while bin three is cooking.

When bin three has settled significantly, repeat the process, turning bin three into bin four, etc. By the time the material has reheated in bin four and cooled you will have finished or close-to-finished compost At any point during this turning that resistant, unrotted material is discovered, instead of pa.s.sing it on, it may be thrown back to an earlier bin to go through yet another decomposition stage. Perhaps the cleverest design of this type takes advantage of any significant slope or hill available to a lazy gardener and places a series of separate bins one above the next, eliminating any need for removable side-slats while making tossing compost down to the next container relatively easy.

A simply constructed alternative avoids making removable slats between bins or of lifting the material over the walls to toss it from bin to bin. Here, each bin is treated as a separate and discrete compost process. When it is time to turn the heap, the front is removed and the heap is turned right back into its original container. To accomplish this it may be necessary to first shovel about half of the material out of the bin onto a work area, then turn what is remaining in the bin and then cover it with what was shoveled out. Gradually the material in the bin shrinks and decomposes. When finished, the compost will fill only a small fraction of the bin's volume.

My clever students at the Urban Farm Cla.s.s, University of Oregon have made a very inexpensive compost bin structure of this type using recycled industrial wood pallets. They are held erect by nailing them to pressure-treated fence posts sunk into the earth.

The removable doors are also pallets, hooked on with bailing wire.

The flimsy pallets rot in a couple of years but obtaining more free pallets is easy. If I were building a more finished three or four bin series, I would use rot-resistant wood like cedar and/or thoroughly paint the wood with a non-phytotoxic wood preservative like Cuprinol (copper napthanate). Cuprinol is not as permanent as other types of wood preservatives and may have to be reapplied every two or three years.

Bins reduce moisture loss and wood bins have the additional advantage of being fairly good thermal insulators: one inch of wood is as much insulation as one foot of solid concrete. Composting containers also have a potential disadvantage-reducing air flow, slowing decomposition, and possibly making the process go anaerobic.

Should this happen air flow can be improved by supporting the heap on a slatted floor made of up-ended Cuprinol-treated 2 x 4's about three inches apart tacked into the back wall. Air ducts, inexpensively made from perforated plastic septic system leach line, are laid between the slats to greatly enhance air flow. I wouldn't initially build a bin array with ducted floors; these can be added as an afterthought if necessary.

Much simpler bins can be constructed out of 2" x 4" mesh x 36" or 48" high strong, welded wire fencing commonly called "turkey wire,"

or "hog wire." The fencing is formed into cylinders four to five feet in diameter. I think a serious gardener might need one five-foot circle and two, four-foot diameter ones. Turkey wire is stiff enough to support itself when formed into a circle by hooking the fencing upon itself. This home-rolled wire bin system is the least expensive of all.

As compostable materials are available, the wire circle is gradually filled. Once the bin has been loaded and has settled somewhat, the wire may be unhooked and peeled away; the material will hold itself in a cylindrical shape without further support. After a month or two the heap will have settled significantly and will be ready to be turned into a smaller wire cylinder. Again, the material is allowed to settle and then, if desired, the wire may be removed to be used again to form another neatly-shaped heap.

Wire-enclosed heaps encourage air circulation, but can also encourage drying out. Their proper location is in full shade. In hot, dry climates, moisture retention can be improved by wrapping a length of plastic sheeting around the outside of the circle and if necessary, by draping another plastic sheet over the top. However, doing this limits air flow and prevents removal of the wire support You may have to experiment with how much moisture-retention the heap can stand without going anaerobic. To calculate the length of wire (circ.u.mference) necessary to enclose any desired diameter, use the formula Circ.u.mference = Diameter x 3.14. For example, to make a five-foot circle: 5 x 3.14 = approximately 16 feet of wire.

With the exception of the "tumbler," commercially made compost bins are derived from one of these two systems. Usually the factory-made wire bins are formed into rectangles instead of circles and may be made of PVC coated steel instead of galvanized wire. I see no advantage in buying a wire bin over making one, other than supporting unnecessary stages of manufacture and distribution by spending more money. Turkey wire fencing is relatively inexpensive and easy enough to find at farm supply and fencing stores. The last time I purchased any it was sold by the lineal foot much as hardware cloth is dispensed at hardware and building supply stores.

Manufactured solid-sided bins are usually constructed of sheet steel or recycled plastic. In cool climates there is an advantage to tightly constructed plastic walls that retain heat and facilitate decomposition of smaller thermal ma.s.ses. Precise construction also prevents access by larger vermin and pets. Mice, on the other hand, are capable of squeezing through amazingly small openings.