Prehistoric farming people discovered that if they mixed manure from their domesticated animals with straw and other organic waste, such as crop residues, the mixture would gradually change into a fertile soil-like material that was good for crops. Composting remained a basic activity of farming until the twentieth century, when various synthetic fertilizers were found to provide many of the nutrients occurring naturally in compost.
The steadily increasing population of the world has come to require large supplies of food. In order to increase productivity, farmers have come to depend on synthetic fertilizers made in factories from nonrenewable resources. However, regular use of these fertilizers does not improve the structure of the soil, and can, in fact, gradually harm the soil. Also, synthetic fertilizers are expensive, an important consideration to farmers in less developed countries.
It was in an underdeveloped country—India—that modern composting got its big start. Sir Albert Howard, a government agronomist, developed the socalled Indore method, named after a city in southern India. His method calls for three parts garden clippings to one part manure or kitchen waste arranged in layers and mixed periodically. Howard published his ideas on organic gardening in the 1940 book An Agricultural Testament.
The first articulate advocate of Howard's method in the United States was J.I. Rodale (1898-1971), founder of Organic Gardening magazine. These two men made composting popular with gardeners who prefer not to use synthetic fertilizers.
People are attracted to composting for a variety of reasons. Many wish to improve their soil or help the environment. Compost mixed with soil makes it darker, allowing it to warm up faster in the spring. Compost adds numerous naturally occurring nutrients to the soil. It improves soil quality by making the structure granular, so that oxygen is retained between the granules. In addition, compost holds moisture. This is good for plants, of course, but it is also good for the environment because it produces a soil into which rain easily soaks. When water cannot soak directly into soil, it runs across the surface, carrying away soil granules and thus eroding the soil. In addition, the use of compost limits the use of natural gas, petrochemicals, and other nonrenewable resources that are used in making synthetic fertilizers. Composting also recycles organic materials that might otherwise be sent to landfills.
Despite its many benefits, making and using compost does have its disadvantages. Composting releases methane, a greenhouse gas which traps solar heat in the earth's atmosphere and may contribute to global warming. The kitchen wastes and warmth of compost heaps may attract pests such mice, rats, and raccoons.