As autumn leaves begin to fall, it may be the ideal opportunity to start your compost pile. Landscape waste accounts for about 20 percent of the typical homeowner’s garbage. Add to this kitchen waste from the produce department and composting can make a significant dent in how much goes to the landfill. In addition, compost benefits the garden by improving soil structure and adding needed nutrients.
The process of composting involves making organic waste available to the denizens of the soil food web. Like us, all of these critters need oxygen to live. The organisms’ activity generates heat which rises to the top of the compost heap. This draws more oxygen into the pile and so the process continues until the waste has been transformed into “black gold.” Left unattended, this takes 12 to 18 months. However, a carefully maintained pile may transform yard waste in as little as four weeks.
The untended compost heap. It works, eventually!
To get off to a great start one needs a mixture of “green” and “brown” materials. “Greens” are materials rich in nitrogen, such as grass clippings, coffee grounds and vegetable and fruit scraps. “Browns,” which contain lots of carbon, include fallen leaves, pine needles, hay or straw and chipped bark. Microorganisms use carbon for energy. They also need nitrogen to reproduce. Joe Average Microbe uses about 30 parts of carbon for every one of nitrogen. Thus the ideal compost pile is composed of materials that add up to a 30:1 carbon-to-nitrogen ratio.
In nature nothing has a 30:1 ratio so we must balance a mix of greens and browns to approximate it. For example, fallen leaves, which are classified as brown, have a 40:1 ratio while grass clippings weigh in at 20:1.
(Photo: A USDA chart showing denizens of the dirt. Click it to go to my July 7 article on soil makeup.)
Thus a pile that is half leaves and half grass would achieve the goal. Add kitchen waste from produce, coffee grounds, tealeaves and eggshells. Garden cleanup contributes more material. Breaking up twigs and shredding leaves to expose more surface area to the decomposers speeds the process. Do not add weeds that have gone to seed, foliage that is diseased, plant material that has been treated with pesticides, or anything from black walnut trees. (Remember why? If not, click the photo below to go to my Sept. 7 column on black walnuts.)
To build the compost pile, start with 4 to 6 inches of course material such as bark and twigs. This allows air into the pile. Cover that with 3 to 4 inches of green material. Then add 3 to 4 inches of leaves. Continue to layer as material becomes available.
Water the pile. It should be damp not soggy. We cannot control the rain. When the pile becomes sodden, turn it to let in fresh air. Turn the pile at least twice monthly to aerate and move material into the center. A pile that is never turned will decompose very slowly.
Does your compost pile need a structure? A bin may speed the process by holding a larger volume of material together which allows more heat to be generated in the center of the pile, but it is not essential. “Lasagna” gardening is basically composting in place. Lay down a layer of brown, cover with a layer of green, wait a few months and compost will be there waiting.
Master gardener Ann Bartlett never lets lack of familiarity with a plant stop her from trying it in the ornamental beds around her home. Contact her at email@example.com.