Story by Jodi Anderson
Compost provides the full spectrum of nutrients that your garden needs, even beyond what organic fertilizers can. The microorganisms in your compost will enable your plants to absorb the nutrients from fertilizers more efficiently, and the nutrients are available over time, as your plants need them. Compost protects your plants from many soil pathogens. Plus, composting is only as complicated as you want it to be. However, there are some factors to consider when tending to your compost pile during the cold winter months.
To create a compost pile in a short time, you need to consider a balance of four things: carbon, nitrogen, water, and oxygen. Carbon provides food for microorganisms. Examples of dry, tough, and fibrous carbon material include dry leaves, rotted hay, straw, sawdust, shredded paper, wood chips, and cornstalks. An active compost pile has lots of high-carbon “brown” materials. Layers of carbon-rich material are especially important in keeping your pile decomposing during winter months. The larger, fluffier bits of dry leaves and other brown material act like down in a winter coat, allowing oxygen to flow while keeping the microbes insulated.
High-nitrogen materials—such as fresh-pulled weeds, grass clippings, kelp meal, seaweed, and manure—provide the protein-rich components that feed microorganisms to grow and multiply. During the winter, you will produce more high-nitrogen ”green” materials (e.g., kitchen scraps, over-ripe vegetables and fruits, coffee grounds and paper filters, tea leaves and bags, and eggshells), so it is crucial to make sure you have plenty of carbon-rich material to compensate. Leave a hole in the top of the brown materials as a place to deposit your green materials. Then, pull leaves up and over the hole to create brown-green layering.
Microorganisms require moisture to work, but balance is essential. Too much water will drown them; too little will dehydrate them. A good guideline is to keep the pile wet as a well-wrung sponge. Maintaining this balance can be challenging in regions that experience rain and snow during the winter months. Using an enclosed container, such as a tumbler, or building your pile on a raised wooden platform and covering it with a tarp will make keeping the appropriate moisture level easier. Even a tumbler will take on moisture, make sure to monitor the moisture balance and add brown material to absorb any excess.
Finally, oxygen is an important factor to consider. Microorganisms require a lot of oxygen to do their work efficiently. When you start your pile, oxygen will be plentiful, especially if you have properly layered the brown and green materials. However, as microbes break down the materials, they will consume oxygen and turn sluggish. Turn your compost pile every few days to ensure that materials are broken into sizes of a half an inch. This will keep the pile aerated and reduce odor, especially as the temperature increases with the spring approach.
Not all organic material is compostable. Woody twigs and branches larger than a quarter-inch can be composted but should be put through a chipper-shredder first. Avoid wood and leaves from plants such as pine, spruce, juniper, and arborvitae and plants treated with weed killer. Commercial composters can handle foods that backyard compost piles cannot without odor or nuisance animal problems. Avoid throwing dairy products, meat of any kind, bones, and foods containing oils and fats (e.g., peanut butter, lard, salad dressing, etc.) into your compost pile.
If you are not using a tumbler and you want to get the most out of your compost, build the pile to three or four feet on each side. Allowing retention of generated heat and air diffusion. Alternate brown and green material layers. Sprinkle a little water on each layer. You may want to throw in a handful or two of topsoil, as well, to get a head start on microorganisms. Approximately 64 cubic feet of material is needed to maintain a hot composting pile in cold regions like the upper Midwest and New England. The size of the material may be more than you want to manage. In that case, the smaller pile will freeze and cease to decompose until warmer temperatures thaw it, and the microbes get back to work.
Temperature control is a must to maintain an active pile during the winter. You can measure the temperature with a compost thermometer. In the cold months, move your pile to a sunny part of your yard and away from direct winds. Keep it in a place that is conveniently away from your home. (You may want to build a windbreaker out of bales of straw; keep the south side open to get as much sun as possible.) A temperature between 90 and 140 degrees Fahrenheit indicates rapid decomposition. During the colder months, decomposition will slow due to lower temperatures, but you can increase activity by adding those green materials and turning the pile.
Primarily, three types of microbes work to digest the materials in a compost pile, and each performs best at a particular temperature range. Psychrophiles do their best work in colder temperatures down to about 28 degrees Fahrenheit. As they digest carbon-rich material, they give off heat and raise the temperature of the pile.
When the temperature reaches 60-70 degrees Fahrenheit, mesophilic bacteria get to work. They are the workhorses of the microbes, responsible for most of the decomposition. A proper balance of carbon, nitrogen, moisture, and oxygen is essential to their success. As they work, they also give off heat and can raise the pile’s temperature to about 100 degrees Fahrenheit.
Then, it’s the thermophilic bacteria’s turn. Tracking the pile’s temperature is even more important at this stage because these bacteria will raise the temperature further to sterilize the compost and kill disease-causing organisms and weed seeds. Three to five days of around 155 degrees Fahrenheit will be plenty to enable the thermophiles to do their best work.
Because you have been managing your pile over the winter, you will have plenty of compost for your garden and lawn in the spring. If you have not mulched your garden in the fall, spread the compost over your garden bed about two weeks before planting. If you do not have enough compost for a full covering, consider “side-dressing.” Sprinkle compost around each plant or along individual rows in late spring or early summer. Top-dress a lawn with a half-inch layer of compost in early spring to have a much healthier lawn for the rest of the year. Spread a half to a one-inch layer of compost around trees or shrubs to the drip line, then cover with a mulch layer to keep the compost from drying out and keep it in place.
Compost is the ultimate material for a healthy, thriving garden or lawn. It revitalizes the soil and helps plants naturally resist disease, insects, and other environmental pressures. Maintaining a compost pile is only as complex as you make it, but when managing it over the winter, make sure you balance nitrogen, carbon, moisture, oxygen, and temperature for an active pile that will feed your soil in the spring.