By Dan Rahn
University of Georgia

Vegetable gardens and landscapes alike can benefit from a generous dose of compost now and then. An excellent source of "slow release" nutrients, compost also loosens tight, compacted soils and helps them hold nutrients.

Bob Westerfield, the University of Georgia Cooperative Extension state consumer horticulturist, said gardeners would probably use more of it, except that they need so much of it (20 to 30 pounds per 100 square feet).

You can sometimes get large amounts in bulk at county landfills and other sites, he said, but getting it home can be a challenge, and it isn't available everywhere. If you don't have an easy supply available from your county, the next best thing is to make your own.

What it is

Simply put, he said, compost is what's left of organic matter after microbes have thoroughly decomposed it. Plants and other vegetative materials are excellent sources of organic matter.

Among the compostable organic materials close to home are leaves, grass clippings, twigs, chopped brush, straw, sawdust, vegetable plants, culled vegetables from the garden and fruit and vegetable peelings and coffee grounds from the kitchen.

Table scraps containing meat, eggs or oils aren't recommended, Westerfield said. They can draw rodents to the pile and smell bad, too. Egg shells are OK, but in general, use only kitchen scraps that are either plants or paper.

The guys that do the actual composting, he said, are bacteria and fungi you can't see with the naked eye. A number of companies sell "composting microbes," but you don't need them. Fortunately, plenty of these microbes are around already.

How to start

Just mix a few scoops of garden soil or compost from a previous batch into the compost pile will provide all the microbes you need to start the process. The microbes just need water, oxygen and nutrients to grow and multiply.

Rainfall will provide most of the needed moisture. You may need to hand water the pile on occasion, too, during dry times, Westerfield said. For the best results, keep the pile moist but not soggy.

The right mix of organic matter can provide all the nutrients needed. Alternate brown and green materials to provide the needed amounts of carbon and nitrogen. If the pile seems to be decomposing too slowly, raise the nitrogen level by adding a few more green materials or a handful of granular fertilizer.

'Air' condition

The best composting microbes require oxygen, he said. There's plenty of that in the air. As microbes decompose organic matter, though, they deplete the oxygen in the pile. So you have to turn the pile routinely to provide more oxygen. The more you turn the pile, the faster it will decompose.

With the right blend of organic matter, water and air, Westerfield said, the microbes release powerful digesting enzymes. After the enzymes break the organic matter down into small molecules, the microbes absorb these molecules and use them for energy and reproduction.

This process generates heat, he said. Sustained for several weeks, the heat will kill weed seeds, nematodes and other organisms that can cause disease. This makes compost much better in your yard and garden than noncomposted materials.

Composting is a simple process, Westerfield said. Try it. If you'd like to know more about the process, contact your county office of the UGA Extension Service.

(Dan Rahn is a Cooperative Extension news editor with the University of Georgia College of Agricultural and Environmental Sciences.)