Weymouth, Mass. — For several hours last fall, the gardener worked on what he called his ``year-end compost heap,'' stopping periodically only to wipe the sweat from his brow or slake his thirst at the garden tap. When the job was done and a square of insulating carpet had been thrown on top, he stepped back to eye the pile with feelings of obvious satisfaction.
``That,'' he said, indicating the sizable compost heap, ``is this garden's storage battery.'' By that he meant that all the energy that went into the spent plants during the growing season was being stored in the compost heap, and would be released to energize the next generation of growing plants when it was ultimately spread on the garden.
The analogy is an apt one, but how one likes to describe a compost heap is of little consequence. The important point is that gardeners everywhere should compost yard-generated waste. There are many good reasons for doing so and they all have to do with soil health, plant vigor, and (surprisingly to many) the well-being of the nation's environment.
According to the August issue of BioCycle, the Journal of Waste Recycling, yard waste accounts for between 15 and 30 percent of the nation's garbage, depending on the region. The bulk of yard-generated waste can be easily composted, which suggests that the strain on sanitary landfills could be dramatically reduced if every homeowner kept an ongoing compost heap.
The immediate benefits for the homeowner, however, lie in the garden. The stepped-up investigation of composting at universities in recent years is backing up what generations of organic gardeners and farmers have known from observation: Compost not only improves soil structure, but also feeds plants and creates a healthy environment all round.
Studies have shown that compost accomplishes a series of seemingly paradoxical things: while it suppresses nematodes and other harmful soil organisms, it boosts beneficial organisms; while it binds heavy metals and other toxins firmly in the soil, it releases nutrients that might otherwise remain locked up and unavailable to plants; while it raises the pH of acid soils, it lowers the pH of alkaline soils, bringing both to the near-neutral level; while it improves drainage in heavy clay soils, it adds water-holding qualities to sandy soils. In a word, it brings balance to the soil.
In its final, most stable form (when further breakdown is extremely slow), compost is called humus -- a dark brown/black soil, ``the fat of the land,'' or ``the organic coloid that causes soil to live,'' as it has variously been described. En route to becoming humus, compost performs some very useful functions in the soil. So it can, and should, be used long before it becomes pure humus. Though still valuable as a soil conditioner, it has lost much of its nutrient value by the time it becomes humus, particularly if it has been exposed to the rain.
To get the most from your compost heap you should start using it the moment the materials that went in are no longer recognizable. At this stage many gardeners sift the compost, adding the fine material to the garden soil while spreading the coarser material as a surface mulch. Others use the coarse material to begin a new compost pile. On the other hand, shredder owners mill the compost at this stage, turning it into the fine looking material you buy at garden centers for $5 and more a bag.
Most gardeners keep an ongoing compost program going year round but make their biggest pile in the fall when so many ingredients are available.
A simple approach is to make a three-sided cage using chicken wire and wooden or metal stakes at the corners. Make it a minimum of three feet square and four feet high if you have a small suburban yard; larger if you have a bigger garden or easy access to plenty of compostible material. Another option is to make free-standing cylinders that are three or four feet or more in diameter out of wire fencing. Just remember, the bigger the pile the better it will heat up and the quicker it will decompose. In huge municipal composting systems, composts can get so hot that they all but destroy themselves, but this is seldom the case in a garden pile.
What goes into a compost pile? Anything that once grew, except large hunks of wood, which take far too long to rot away. Grass, weeds, spent plants, hedge prunings, and leaves, along with kitchen waste, are the most commonly available materials.
Compost purists discuss such things as the carbon-nitrogen ratio needed for good decomposition. Forget about that unless you are into chemistry. Just remember that dry materials are high in carbon and lush green growth high in nitrogen. You need to mix the two to get a good compost heap going. Manure, feathermeal, or fishmeal, anything that is high in protein, are all good substitutes for green materials. Kitchen wastes also qualify as nitrogen rich materials.
Start your year-end compost heap by sorting out the materials available -- dry in one pile, green in the other. Now start building the pile in layers -- first spread a six-inch layer of dry matter and top that off with a similar layer of green. Some people sprinkle on a shovelful of soil at this stage, too. It's helpful, but not vital to composting success. If you run out of green material, a one-inch layer of manure will do. Or sprinkle on any other of the nitrogen-rich materials the way you might sprinkle sugar on cereal. If, on the other hand, you have too much green waste, place five or six sheets of wet newspaper between each green layer and this will add the necessary carbon to the pile.
Continue building up the heap layer by layer until it reaches the top of the cage. Now if the materials are basically dry, water the pile thoroughly. A good compost is always moist, though never soggy. Finally, throw a piece of old carpeting or thick blanket over the top. The heap will begin to heat up within a few days as decomposition begins and the carpet will help contain it within the pile. Otherwise, a six-inch layer of soil will do.
Now you can leave the compost heap just as it is. Within six months in the warmer South it will be ready to use; in the colder North, winter will slow down the decomposition somewhat, but even so it should be ready to use by the end of May.