Making Compost

There are relatively fast methods of making compost which require a fair, but not unreasonable, amount of effort and attention, and then there are slower but less arduous methods. In both cases the process by which garden refuse, kitchen garbage, manure, yard trimmings, and decomposable trash are transmuted into the black gold of compost is similar. Whether a freestanding compost pile is built, or the materials are kept in a bin or other enclosure during the composting process is immaterial; only the appearance is different.

The fast method is like building a fire, and it differs from the slow method solely in that air is actively incorporated into the pile. The fuel is carbon: dry plant matter like leaves, straw, hay, or dry weeds and yard trimmings. The heat comes from nitrogen. The surest form of nitrogen to fuel the compost pile is manure. Where it is available it should be used (with the exception of manure from pets or people, which, unless specially treated, may contain disease pathogens). Where manure is not available the readiest sources of nitrogen are freshly cut grass clippings, freshly pulled weeds, and kitchen garbage: that is, vegetable and fruit trimmings, coffee grounds, spoiled leftovers, and the like. It also makes sense to include a bit of soil or compost from an earlier pile, which will serve as a “starter” by providing a population of decomposing organisms earlyon (though they would eventually find the pile anyway). Such compost starters can also be bought ready-made if a starter source isn’t available.

Two last elements that are important are moisture, and the size and shape of the pile. The microorganisms that drive the composting process forward require moisture. If the materials used are not succulent, the pile should be watered as it is built, and periodically there after, to keep it uniformly moist. When the materials are just glistening and damp to the touch, but not soaking wet, conditions are likely to be ideal. The size and shape of the pile become important as it heats up (which increases the biological activity within speeds along the composting) because the pile must have enough bulk in relation to its surface area so that it generates more heat than it loses. Many experienced composters actually insulate their piles with a layer of straw or manure to conserve its natural heat. An effective minimum size for freestanding piles seems to be about four feet on a side (or longer if you need more compost) and about four feet in height. Some commercially manufactured compost bins are insulated, and so make it possible for a smaller volume of material to attain the critical heat levels needed for fast composting.

Table 4–2

Carbon/Nitrogen Ratio of Common Compost Materials

Material                                              C/N Ratio

Grass Clippings                                   20 to 1

Weeds (green)                                     19 to 1

Leaves                                                 60 to 1

Paper                                                   180 to 1

Kitchen Scraps                                    15 to 1

Sawdust                                              450 to 1

Hen Manure (no litter)                        7 to 1

Hen Manure (w/litter)                         10 to 1

Straw                                                   100 to 1

Seaweed                                              25 to 1

Pines Needles                                      70 to 1

Corn Stalks                                         60 to 1

Alfalfa Hay                                         13 to 1

The ingredients should be kept in proper proportion when assembling a compost pile. A common rule of thumb is that you’ll want, by volume, four to five times as much carbon-rich material as there is nitrogen-rich refuse. These difference kinds of materials are kept well mixed by layering them on the pile as they are collected. Two of the most common products of the American yard, however, require special attention. Autumn leaves, unless shredded before piling, tend to pack down and exclude air; lawn clippings are so rich and succulent that, unless dried first or mixed thoroughly with drier material, they will rot into a slimy mess instead of composting. Both materials are excellent sources of nutrients, though, and composting them saves money and landfill space, at the same time providing nutrients for your garden.

One of the more difficult tasks in composting is to make sure that air can get to all parts of the pile throughout the decomposition process. The bottom layer of the pile should be made of shrub prunings, twigs, or other light materials. As the pile increases in size, larger branches or even poles can be laid horizontally on top, and then later, during its decomposition, withdrawn to allow air to enter. Some other methods of getting air into a compost pile to speed its decomposition are to stick vertical lengths of drainage tile into the first few layers of the pile and then build it right up around them; or to poke holes with a bar or piece of iron pipe once the pile is finished; or, as many gardeners do, turn the pile with a manure fork each time it starts to cool down, placing the materials from the outside of the pile on the inside and vice versa. For gardeners with limited space and fairly formal yards, there are manufactured compost tumblers that will accomplish this process of reaeration without the heavy lifting.

The basic proportion between the dry, fuel-type materials in the pile and the moister, heat-supplying materials should be four or five to one. The soil or compost fraction usually covers lightly each layer of the nitrogenous material to hold in its moisture and discourage scavenging animals (not a problem if a bin is used to hold the compost). In our hot piles we alternate six to eight-inch layers of dry matter with one to two-inch layers of manure and one-half to one-inch layers of compost from the previous pile. Many composters, including us, like to add a bit of phosphorus to the pile, as it is proportionately low in both compost and manure. We use rock phosphate, and sprinkle three or four handfuls over the compost layer before starting again with the dry layer. Piles that use no manure tend to be a bit more acidic, and wood ash or bone meal would make a good addition, as they would effectively raise the pH toward neutral a bit.

This layering process should continue until the pile is four feet tall. Water it if necessary to ensure that there is sufficient moisture for decomposition to proceed. Within a few days the pile should begin to heat noticeably. During cool weather it may actually steam, but during the spring and summer months (when composting proceeds most quickly, anyway) you can check it simply by thrusting your fist into the pile. In the center it may well be too hot to touch, between 120˚ and 140˚ F (49˚ and 60˚ C). Once it begins to cool down—if you want to keep the process moving as quickly as possible—consider supplying more air, either by turning the pile, or by the other methods mentioned above. If you are of a precise mind, you can check its progress with a thermometer. We use a small, inexpensive meat thermometer: after thrusting my fist into the pile, I stick the thermometer into the end of the passage so that it is within the heart of the pile. As soon as the temperature drops below 100˚ F (38˚ C), I consider the pile ready for turning.

A properly proportioned pile, made with the right ingredients and closely managed, can be ready for use in as little as two weeks, having been turned twice or three times over that period. This is particularly true if the materials from which the pile is built are shredded before composting; the smaller particle size makes the work of decomposition easier for the microorganisms in the pile. If you have a garden spot that you want to improve as quickly as possible, simply scour the neighborhood for leaves, hay, stable cleanings, sawdust, and manure, rent a shredder, and make a whole series of piles.Even without turning—if you build the piles properly, with provision for getting air to the center—you should be able to produce large amounts of ripe compost in a month.

My grandfather’s garden was well established by the time I was born, and he had his methods so well worked out that this kind of hurry-up composting was unnecessary. Instead he had adopted a method of slow composting that, while it took quite a while to produce finished compost, yielded him a steady supply with very little labor. He called it the “lazy man’s method,” and being lazy myself, it’s my method of choice as well.

Start by laying out a rectangle about five feet by twelve feet on a level piece of well-drained ground, marking the corners with stakes. Then lay up an outside wall of one or two thicknesses of sod or cement blocks. The system requires the maintenance of three compost piles, one of which is available for current use, one of which ages for a year, and a third which is being built during the current season.

Build the pile using all decomposable garbage from the house, and from your neighbors as well, if you can get them to sort their waste, covering each layer with a layer of hay or leaves and a thinner layer of topsoil before it has a chance to become nasty. Early in the spring there will not be much beyond kitchen scraps to put on the pile, but as summer comes on there will be garden weeds, pea vines, etc. As the pile grows, keep building up the sides with sods or other material that will stay in place, and keep covering the succeeding layers with topsoil, or, if available, with thin layers of manure.

In the fall put all the crop wastes from the garden onto the pile: squash, tomato, and bean vines; the remains of cabbages, cauliflowers, broccoli; and so forth. At the end of the season, cover the pile with sods root-side up (so they won’t grow), or with manure, and then leave it for nature to take its course. By the time the pile is two years old, having taken six months to build and eighteen months to cure, it should be fully decomposed; any material that is not can be placed on the bottom of the new pile.

This kind of composting is also called anaerobic composting because it proceeds without worrying about getting air into the pile. It is essentially controlled rotting, and, as my grandfather was fond of pointing out, the only real difference between well-rotted manure and compost is that the manure went through the gut of an animal first. Both began as vegetation, but the manure was predigested by the gut bacteria, acids, and enzymes of the animal before being deposited and allowed to rot. The process of both rotting and composting is digestion, and either rotten manure or plant compost can be used to fertilize and improve the soil structure of your garden. Which you will use depends largely—as does the method of composting you choose—on the particulars of your situation.

If you have access to good rotted manure, or a place to compost it, it is the simplest product to use; if not, then composting will provide you with just as many of the benefits, though with a bit more effort. If you have plenty of space and abundant raw materials, but are short of time to manage a quick compost pile (or just don’t need that much compost), by all means follow my grandfather’s long-term, low-work method.

ShepherdMaking Compost

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