A Greenville gardener used to live in a place where he had space enough to keep a vegetable garden twice as big as required to feed his family. Each year, one half of his garden was devoted to a cover crop — two complete cycles of buckwheat. The other half was used to grow vegetables. The sides were reversed in the following season, and in this way his soil was kept in tip-top condition.

Now the unfortunate horticulturist has space for only two raised beds. Consequently, he has an interest in making compost to improve his soil’s tilth and fertility. He has seen advertised a number of barrel composters, all too expensive for his budget, and he would like to build a composter of his own. The question is: what are the principles of barrel composting and how do they dictate the design of a home-built composter?

The typical claim one reads about barrel composters is that they produce rich, usable compost in just 10 days to two weeks. Depending on the time of year and the material being composted, I have no doubt that this speedy composting is possible, if all conditions are optimum.

Optimum conditions for composting organic matter would be plenty of moisture (but not so much that you can easily squeeze drops of free water out of the mix), well chopped organic matter, adequate nitrogen and other nutrients and full aeration of the mixture. Warm temperatures will also speed the process, although a well constructed system will generate plenty of heat on its own.

There is nothing magical about using a barrel to make compost; it just so happens that barrels make it easy to maintain the right conditions for rapid composting, because they retain moisture and can be turned easily to promote aeration of the contents.

The simplest form of barrel composter sits on the ground and is rolled around periodically (once or twice a day is sufficient) to keep the contents aerated. Surplus plastic barrels (used to ship frozen juice concentrate from South America, mostly) are often sold cheaply at flea markets and salvage operations, and they make ideal composters.

To turn a barrel into a composter you will need to make a door in the side or end and devise some method of keeping the door closed. Bungee cords or duct tape can be used. Two or three dozen holes 1/4-inch in diameter should be drilled around the outside of the barrel to allow air in. Finally, it is desirable but not absolutely necessary to apply some paddles or vanes to the inside of the barrel so that when it is turned, the contents will be mixed and fluffed a bit.

If rolling the barrel composter on the ground seems too primitive, you might make a cradle for the barrel to sit in and then mount rollers, wheels or casters in the bottom to facilitate turning. A crank or wheel can be added to one end of the barrel for the Cadillac touch.

A nice addition to a barrel composter would be a thermometer, since the best way to monitor the progress of the composting is by taking its temperature. Temperatures inside the barrel may go as high as 140 or even 160 degrees, so be sure your thermometer goes that high. The thermometer is inserted into the composting mass after turning and removed before the next turning. A well-made compost mixture will heat up in just a day or two and by tracking its temperature you can tell when the composting is completing (temperature falls below 100 degrees or so). Of course, you can use your hand to keep track of temperature in a general way.

Having built your barrel composter, you will soon discover that the real art (science, more aptly) of composting lies in making the right blend of ingredients not just keeping them at optimum conditions. I suggest that anyone interested in going this route contact the University of Maine’s Cooperative Extension Program (look in the phone book under your county’s name) for literature on composting. Also the library is a good place to find a book on composting.

Michael Zuck of Bangor is a horticulturist and the NEWS garden columnist. Send inquiries to him at 2106 Essex St., Bangor, Maine 04401.