COMPOSTING AND SOIL FERTILITY

The typical gardener is far less inclined to examine soil and compost under a laboratory microscope, in a test tube, or under a mass spectrometer than to fondle them lovingly in the garden. For most of us, composting, soil chemistry, soil fertility, and even soil biology are subjects more easily experienced directly, and participated in, than explained or catalogued comprehensively, for they involve worlds of mystery that even intrepid scientific explorers can only begin to understand. This section will provide only a broad overview, along with some practical specifics. More thorough treatments of these subjects are available in many excellent sources already, including John Jeavons’ How to Grow More Vegetables…, The Soul of Soil by Grace Gershuny and Joseph Smillie, Start with the Soil and The Rodale Book of Composting by Grace Gershuny, Joseph Jenkins’ The Humanure Handbook, and Uday Bhawalkar’s Turning Garbage Into Gold, among others.

Many gardening practices can contribute to a healthy soil and to rich nutrient content for the vegetables growing in it. In almost every case, adding organic matter (unless it is overly acidic, toxic, or counterindicated in some other way) serves to improve the soil’s structure, its nutrient content, and its ability to host many forms of life (see the Beetless' A HARD CLAY SOIL [0] and YOU'RE GONNA LOSE THAT SOIL [0]). This organic matter can come in the form of a mulch (see the Bed Preparation Methods [0] section, and also IT'S ALL GOOD MULCH [0], MULCH! [0], and PAPERBACK MULCHER [0]), or from the residues of above- and below-ground parts of plants that die on their own or are weeded or cut and left to decompose (see PLEASE WEED ME [0]). It can come in the form of cover crops (in summer, most commonly buckwheat; overwinter, most commonly clover, vetch, annual rye or other grains, field peas, and favas) which are either incorporated into the soil or cut and laid on top. (For maximum nitrogen content and benefit for the soil, the crop is generally cut when it is fifty-percent flowering.) It can come from those same plants (weeds, expired vegetable plants, cover crops) made into compost, perhaps in combination with food scraps, manure, old hay, and other organic materials. It can also come from straight composted manure, like that which inspired the Beetless to start singing about THE TURD [0]. During many seasons, we have used composted chicken manure as a main source of organic matter and nutrients, and have composted and used other animal manures as well when we could obtain them.

We have generally constructed our compost piles like layer cakes, in a process quite reminiscent of baking. We start with a layer of coarse material (like old fennel stalks) on the bottom, to aid drainage. Then we alternate approximately equal layers of green (relatively more nitrogenous) materials, like weeds, grass clippings, and food scraps, with layers of brown (more carbonaceous) materials, like hay, straw, or dry grass. Every few layers we may insert compost or manure, to inoculate the pile with more composting organisms.

We make sure that the pile is adequately large to compost (it needs a minimum thermal mass to heat up satisfactorily), but not so large that it excludes air from the center or squeezes air out of itself. We build each free-standing pile at least four (but usually not more than five) feet wide in one direction, and generally keep its finished height to about four or five feet as well. It should be at least four feet long in the other direction, but can be quite a bit longer than that; the five-foot-or-so maximum thickness need apply in only two directions.

The ideal pile is built all at once, so that the large thermal mass has a chance to heat up all together, rather than being added to bit by bit. In preparation for this technique, green materials, brown materials, food scraps, and manure or compost can be stored separately until adequate quantities are ready to make a complete compost pile from them. However, practical considerations have also led us to build some piles in stages instead, still trying to add as much as possible at any one time. They don’t heat up quite as well, but they eventually turn into compost anyway. We have also added height to piles several times after they have shrunk (which they do, typically to half their initial height, or even shorter).

On each layer of free-standing piles, we build the edges first, then the middle. This helps us keep the pile wide in all directions as it is built up (we don’t want it to taper any more than is inevitable), and keeps the edges from falling off as much as they would do if they were placed down after the middle materials. We insert food scraps, when we have them, in the middle, to protect them from animals and to put them where the composting temperatures will be hottest.

The pile needs to maintain the dampness of a wrung-out sponge—not too wet, but not too dry. It may need to be watered, both as it is being built, and as it composts. It is best to keep excess water off of it during the rainy season when it is already moist enough; however, wrapping it in plastic is not the ideal option, because the pile also needs air. A free-standing roof over the compost pile can allow air circulation while protecting from waterlogging.

Composting is sometimes done in bins constructed from wooden pallets or other materials, although this may cut down on the amount of air that is able to penetrate into the pile, and may also limit the size and location of the pile. We have built many compost piles directly on garden beds, where their residues will feed the bed even after the finished piles have been mostly removed. On the other hand, a bin system built in conjunction with a rain-shedding roof may yield the best wintertime compost.

To feed the bacteria that will be performing the composting, the preferred carbon-to-nitrogen ratio of materials going into the pile is approximately 25:1—something that is quite difficult to calculate precisely, but can be judged roughly by consulting C:N ratio charts like that on page 325 of Robert Kourik’s Designing and Maintaining Your Edible Landcape—Naturally and through experience. (The C:N of finished compost is approximately 15:1, because some of the carbon is lost to the atmosphere.) Getting the mix of a compost pile “right” is much like making bread. A recipe may be helpful to get you started, but because materials always vary somewhat, no recipe will get you to the “perfect” pile. After enough experimentation, ultimately “feel” will be your best guide.

Within a few days, the pile may reach temperatures of 160-170 degrees Fahrenheit, as the thermophilic (heat-loving) bacteria go to work. When they’re done with it, the mesophilic bacteria take over, then eventually other organisms, including fungi (name-checked in the Beetless’ I'M A SHROOMER [0], which, however, is mostly about wild mushrooms) and macro-scale decomposers like worms, pillbugs, millipedes, and earwigs. When its constituent parts are indistinguishable and it looks like dark, crumbly humus, it is ready to use. Parts of the pile that are not fully composted can be added to another pile. It is possible to turn (or re-pile) compost piles to speed up composting, but it is not usually necessary if one is not in a rush to get the final product. Turning adds speed by putting the pile through another “hot” phase, but it also reduces the final size as well as nutrient content of the pile (much in the same way that cooking food continuously on a stove destroys more nutrients than slower cooking using a crockpot or a haybox).

Many of composting’s bare-bones essentials are covered in the Beetless’ SHE SAID SHE COMPOSTED IN WINDROWS [0], whose protagonist also adds urine to her compost piles. (Urine is the one material commonly added to compost piles whose C:N ratio is less than 1:1; everything else has more carbon than nitrogen, usually significantly more.) Other parts of the Beetless’ compost-related repertoire, detailed in their APPENDIX [0], include BLUE-GRAY HAY, COMPOST TOGETHER, and TURDS OF LOVE.

Some gardeners prefer moldering composting, in which the pile is added to gradually (usually with less attention to C:N ratios) and doesn’t heat up. This yields humus in the end as well, but will not kill weed seeds or pathogens the way hot composting will, and may break down materials less thoroughly.

Worm composting (vermicomposting), either in bins or on the surface of the soil, is another option. Worm bins, inhabited by manure worms, are generally suitable for individual- or family-scale composting (especially in urban areas where outside piles and bins can pose problems), but to handle the quantities of food scraps that Lost Valley generates, we would probably need to construct a dedicated building-size facility. We have tried soil-level vermicomposting with earthworms (by spreading food scraps on beds and covering with a layer of mulch), but have found that, in our gardens, this attracts raccoons, skunks, and other animals to root around in the beds as they eat the food scraps. Therefore, most of our buckets of food scraps still either feed our chickens or go into compost piles or deeper mulching projects. Earthworms do play important roles in our garden by farming beneficial microorganisms, aerating the soil, and enhancing fertility, as summed up in the Beetless’ EARTHWORM [0].

Although reductionist soil chemistry (see ROLL OVER J. LIEBIG, from the Beetless’ APPENDIX [0]) has been largely discredited as a comprehensive way of understanding what goes on in the soil (having been replaced by a much greater appreciation of soil biology and microbiology), minerals are important. N-P-K (nitrogen-phosphorus-potassium) and calcium are the ones most commonly analyzed and added (in organic forms) to enhance plant growth. Among many other functions, nitrogen is associated with green leafy growth; phosphorus with rooting, flowering, fruiting, and seed formation; potassium with strong stems and general growth; calcium with overall vigor, especially in certain plants, including brassicas and tomatoes. Both phosphorus and nitrogen leach out of soils, and both are contained in quantity in the composted chicken manure with which we commonly amend our beds. Oyster shell flour adds calcium to our soils and helps raise the pH to a more vegetable-friendly range (6.0 to 7.0) from its normal more acidic range. Rock dust adds a whole host of minerals and can bring many benefits, especially in demineralized soils (see the Beetless’ ROCK DUSTING SOON [0] for the full scoop). We have applied it every few years to our gardens.

We have also occasionally prepared and used manure teas, compost teas, and comfrey teas, but (as of fall 2006) not consistently enough to sing about yet. Many gardeners regard time-release sources of plant nutrition like compost and composted manure as healthier for soil and plants than soluble, quick-release sources like some of these teas, which more closely mimic soluble synthetic fertilizers and can also have some of the same undesirable effects (too-rapid plant growth, “burning” of soil organisms and even plants, nitrate pollution). One tea that has no detractors is Equisetum tea, a potent antifungal that can restore health to a disease-stricken greenhouse. And in recent years researchers have been developing new approaches to compost-tea-making whose far more sustainable and ecologically benign goal is to spread beneficial microorganisms, rather than give a rush of soluble nutrients.

If all of the above seems a bit complicated, just remember that, in almost any situation, you can rarely go wrong by spreading a few gallons of finished compost from MAXWELL'S PLASTIC BUCKET [0] and seeing what happens next.

 
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