By Adam Tomash
1. Materials. Brown materials are high in carbon, green materials are high in nitrogen. Mix the two in rough proportions of 2 volumes of brown to 1 volume of green to achieve a C:N ratio of 25:1 to 40:1. Remember that different sources of nitrogen have differing amounts of nitrogen; e.g., alfalfa is 2.6 percent N, blood meal is 12 percent, fish meal is 8 percent, soybean meal is 7 percent, so less of the higher N additives will be needed. Five 50-pound bags of alfalfa meal will take care of the N needs of an 8-foot-diameter compost pile of brown leaves that is 4 to 5 feet high. Put in 4 to 6 inches of loose leaves and cover with a half-inch of alfalfa meal. Repeat until bin is full.
2. Coarseness. The finer the shred, the faster the decomposition. Running leaves through a shredder or lawn mower will make composting happen faster. Coarse twigs and other woody refuse are OK; they help aerate the pile and encourage beneficial fungi.
3. Aeration. The biological processes in the compost pile need fuel (carbon and nitrogen) and air and water to work properly. Whole leaves will sometimes mat and cut off air to the inside of the pile. Use a big crow bar to punch holes in the pile or better yet, tie several 5- or 6-foot sapling poles together and place them in the center of the pile. Spread the “legs” out a little to make a channel for air to enter.
4. Moisture. Use a hose with a fine sprayer to moisten the materials thoroughly before piling. Surround the pile with plastic to retain moisture. After the pile cools a little, you can cover the top as well. Keep checking it; if moisture builds up, remove the cover and/or the plastic wrap.
5. Temperature. The goal is to get the pile to a minimum temperature of 140 F so that plant pathogens and weed seeds are killed. (Organic growers’ piles must meet specific time and temperature requirements. See page 4 of MOFGA Certification Service’s 2012 Organic Certification Practice Manual at http://mofgacertification.files.wordpress.com/2012/01/2012practicemanual.pdf.) If you have the energy, turn the pile so that all materials reach the target temperature.
6. Size. The pile size should be at least 3 feet long, 3 feet wide and 3 feet high. Smaller piles will not heat properly.
7. Vermin. Keeping vermin out of compost piles is a challenge in certain areas. Skunks, raccoons, rats and other animals find compost piles attractive. You can make a compost pile less attractive by not putting animal products, fats, cheese and similar substances in it. To recycle bones, save them in a freezer until you build the pile and then shred them and mix them into the pile as you build it. Feed fat and meat scraps to domestic or wild animals away from your compost. Piles built well away from stonewalls, buildings and other rodent residences will create a challenge for them. Rodents don’t like to cross open ground to feed because of their exposure to predators.
8. Weeds. Witchgrass, sumac and other vegetation will attempt to “raid” your compost pile when it begins to mature and will make recovery of ripe compost more difficult. At a minimum, cover the ground under the pile with VERY heavy-duty landscape cloth. Extend the cloth out away from the edges of the pile a few feet and pin it down with earth staples. Place the compost pile well away from hedgerows with sumac and other invasive plants so that they don’t invade the pile. A concrete slab will eliminate this problem. I have also found that with just a quality woven black plastic landscape cloth under the pile, witchgrass will still send roots up through the cloth into the pile; but with a layer of quality clear or black poly tarp without holes under the landscape cloth, roots just grow laterally under the plastic rather than sending fine roots up through the small gaps in the woven landscape cloth.
9. Time. Nature does not normally make compost but rebuilds the earth by mulching. Processes that occur at an accelerated rate in the heated pile do so at a much slower rate at the interface between soil and mulch. Compost can be made in a short time with lots of labor and human intervention in devices like compost tumblers or with frequent turning. The same results can be had with less effort simply by building a pile and waiting. It can take as long as two years for the resulting compost to bear no resemblance to the organic matter from which it was made. Specific kinds of worms (compost worms or red wigglers) can aid in this final process and create quality compost that looks like fine, crumbly topsoil. If you have worm bins you can rob some worms and “inoculate” piles with a handful. If the pile is big enough they will even survive the winter. Piles will normally attract worms without your intervention. If you find worms in the center of the pile, they are compost worms (red wigglers, Eisenia foetida). Regular “earthworms” will not inhabit the pile.
10. Overuse. Soil can be damaged by overuse of compost but that usually takes heavy applications over long periods. Soil tests can tell if you need to be careful on a given plot. UMaine does complete tests (with organic recommendations if you wish) for a reasonable fee. In particular keep an eye on phosphorus and organic matter levels. The latter should settle down at around 8 percent to have “rich” soil.
11. Fungi. One benefit of using compost instead of chemical fertilizer is the encouragement of beneficial fungi called mycorrhizae. Mycorrhizal fungi set up a symbiotic relationship with plant roots, extending the capabilities of the roots to extract nutrients and water from soil. Mycorrhizae have greater abilities to bring nutrients in a plant-useable form to roots. Many products for gardeners have the prefix “myco” on their labels. The efficacy of such products is not without controversy. You can have the fungus for free.
12. Ion exchange resin. Adding compost enables a soil to hold nutrients that plants need in a way that prevents them from leaching (unlike synthetic chemical fertilizer) but still can make them available to plant roots. When roots contact a rich bit of compost, they thoroughly penetrate the organic matter and release compounds that can displace the nutrients from the organic matter and replace them with products of respiration. This is called ion exchange and resembles the process that happens in a water softener. Soil organic matter is like a savings bank for plant nutrients: The more cash in the bank, the nicer and bigger the vegetable. I personally don’t think most of us gardeners have seen vegetables reach their full potential, because they are rarely in a state of perfect nutrition.
About the author: Adam Tomash and June Zellers have a suburban garden that they wishfully classify as a "research station" for small agriculture.