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by Bob Richards and David Jennings


As organic gardeners know, compost is the most complete organic soil enhancer available, capable of transforming poor soils into rich black loam. The composting process is an important one: it completes nature's cycle by returning garden and kitchen wastes to the soil. However, most home gardeners cannot make compost in sufficient volumes for their needs, especially when they have ornamentals as well as vegetables vying for its beneficial effects. So they find themselves in the garden centers each spring and fall, surveying the rows of bagged soil amendments.

Your spring and fall soil preparation will, to a large extent, determine your gardening success. Since it requires the same effort to till a garden with a poor soil additive as with a quality one, you are ahead in time, effort and money if you do it right.

The astute gardener seeks to improve one very important gardening parameter, the level of organic matter or humus in the soil. The benefits of organic matter include permeability, water retention, optimum nutrient level, good seed germination, proper root development and disease suppression. Manures and peat products will provide some of the required parameters, but only a high quality compost provides them all.

Professional, commercial-scale composters know that composting consists of a little science and a great deal of art. The process is really quite simple. The combination of a carbon source, a nitrogen source and a continuous supply of oxygen will allow those friendly little microbes to devour the raw materials. In the process, they create a humus material that plants adore.

The art of the process is in knowing when to aerate the composting piles, when to turn them, when to add moisture and when to reduce it. Since this is often site-specific and related to climate and other variables, it is a balancing act with a long learning curve, as many would-be commercial composters have discovered. Assuming that good quality raw materials are used, a good compost has been rendered when the resulting material is odorless, black and earthy in texture and appearance, and stable enough to not reheat when piled.

Any compost is only as good as its raw materials. Many large composting sites in North America utilize materials collected from municipalities. These can include leaves from city streets, discarded fruit and vegetables from supermarkets, household organic wastes, food wastes from restaurants, and in some cases even municipal sewage sludges. While all of these materials compost readily when handled properly, and while the resulting product is odorless and looks good to the naked eye, careful examination reveals that it can harbor tin foil, plastics and other undesirable components. In one instance of which we are aware, the business end of a hypodermic needle was found in such compost. You won’t see these composts as bagged products in reputable garden centers but you might see them offered in bulk locally.

By the same token, compost made from food wastes from restaurants, homes and supermarkets will retain all the pesticides or the preservative chemicals that may have been added to the original food. Composts from these materials are quite suitable for landfill cover or commercial landscaping use. The home gardener, however, for whom the garden is a source of food and joy, wants nothing less than a first-class compost.

Always read the ingredients on the bag. A good composter will be able to tell you precisely what the product is made from, with no vagaries or fudging. Shortly, composts sold in Canada will have an A, B or C rating, with A-rated, the best quality, suitable for home gardening. Even then, check the ingredients.

Softwood-bark composts have been shown to be effective in reducing the incidence and severity of many common soil-borne plant diseases. Scientists believe that this is the result of a "penicillin-like" effect. Compost is created when saprophytic fungi and bacteria, those that feed on dead plant and animal material, decompose the raw materials in the compost pile. During this process, there is fierce competition for food and space. As a result, many of these saprophytes give off a substance we know as antibiotics, to control their competition. Pathogenic fungi and bacteria, those that would attack living plants, fall prey to this antibiotic activity and are therefore less prevalent in compost-amended soil.

Next time you face the garden center maze, go directly to the selection of bagged composts. Then read the labels. A good quality compost will have pure, uncontaminated ingredients. There will be no additives, nor will it be bulked up with fiber, peat moss or other benign fillers. When you supplement your own homemade compost with a good quality commercial compost, your garden preparation is complete.


Bob Richards is President of Genesis Organics, the largest dedicated composting site in Canada at Wild Cove, near Corner Brook Newfoundland.

David Jennings is a Field Supervisor with Agriculture Canada and an Agrology Consultant



Copyright 1996. Bob Richards and David Jennings.

Reprinted with permission. All rights reserved.

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