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Carbon essential to compost
Roy Jonsson
Contributing Writer
In our natural world all organic material decomposes into humus over time.
To become a successful composter it is essential to understand this natural process. Dead plants, the basic raw material for backyard composting, contain the element carbon, which is one of the main building blocks found in all living things.
In addition to carbon, plants also contain varying amounts of nitrogen. As a general rule, green plants contain more nitrogen and brown plants have more carbon. Mixing these two organic materials in a green-brown ratio of one to one will produce the best rate of decay in a compost box.
One trick to successful composting is creating as many green and brown layers of material as possible. Never put in more than four to six inches of any one material, even if it means stockpiling material for a week or more. I stockpile many of my fall leaves to add to the kitchen wastes over the winter.
The decay of organic material is caused by a whole host of different creatures. The larger ones usually begin the process by breaking the material down into smaller particles. This allows the smaller ones a greater surface area to work on, gradually reducing the organic material into carbon dioxide, water and organic fertilizer.
Earthworms eat their way through organic material grinding the food in their tiny gizzards and expelling the waste as worm castings or manure. This is why it is important to regularly add a small amount of soil to the compost. One shovel full of soil for every 10 to 15 centimetres of loose fill is plenty. If you add more you might smother the pile and stop the exchange of gases.
Bacteria do the bulk of the work in a compost pile, but not all types of bacteria are desirable. The aerobic or beneficial ones need oxygen, water and heat to function properly, as well as a steady supply of nitrogen to help them break down the complex plant molecules. Keeping the pile aerated allows the bacteria to breathe. Using a sharpened broom handle or stick to punch about a dozen vertical holes in each square metre of compost should eliminate the need for laborious turning. Once the bacteria start their work they generate their own heat, setting up a natural pasteurizing process if the temperature exceeds 55 C for three days. This will only happen if the pile or mass is large enough to generate sufficient bacterial heat. A cubic metre is the optimum size for aerating and heating. Solar heat is helpful but not essential.
Adding water to the pile during periods of rapid heating or in the summer may be necessary. Too much water from heavy winter rainfalls will cool the pile, drive out essential air, leach out valuable nutrients and drown the bacteria. A waterproof cover is best used from November to March.
Keeping a warm, semi-moist compost pile during the coldest part of the winter can make the pile very attractive to rodents who appreciate the built-in central heating. Using a wire-covered or rodent-proof compost box is the easiest solution to this problem. If you suspect there are rats in your compost box, watch for entrance holes at the back and set a trap.
Kitchen waste is a valuable source of nitrogen-rich material, which will add 150 to 200 gallons of raw material per year. Most cooked foods are softer than raw vegetables and therefore disintegrate much more quickly, leaving little to attract rats. Large cabbage cores, whole oranges, onions, etc. should be chopped to speed their breakdown. Eggshells are of little value and they make your garden look like it has been covered with confetti. Both tea bags and coffee filters break down rapidly.
Kitchen wastes to avoid in your compost box are meat, fat, grease, oil, bones and other animal products. Compost bacteria cannot break these materials down under normal conditions. Pet feces also fall into this category because the food pets eat is combined with hair. All garden waste can be used with the exception of infected plants, pernicious weeds, ripe seeds, woody stems, branches, large volumes of lawn moss and some of the hard leaves such as oak, laurel and rhododendron. Hard leaves and other coarse material like fern fronds can be ground up with a power mower and used as mulch.
To avoid difficulties with your compost, the following are a few simple rules to follow.
If the pile smells, there is too little air and you need to poke holes in the pile.
If the pile dries out it could be too hot, so add water.
If the pile is too wet the bacteria will drown and the pile needs a cover.
If the pile is slow to decay or reduce in volume, it could be any of the above, or the bacteria are being starved for lack of nitrogen. Add a few handfuls of high nitrogen fertilizer to speed things up.
Composting not only provides an excellent material for your next growing season but also contributes to a healthier environment.
Roy Jonsson is an avid gardener, horticultural instructor and consultant for residential and commercial properties. He may be reached at roy_jonsson@telus.net.
published on 11/08/2006
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