A renewable resource is one which can be replenished before the existing supply is exhausted. If replenishment of a resource in a usable state costs more than it did to produce or extract the resource in the first place, it is effectively non-renewable. It is important to develop and use techniques that speed replenishment while remaining cost-effective. For this reason, efforts to conserve and replace soil have great value. Composting, vermiculture and storm water runoff prevention efforts all combine to make soil renewal more effective.
The process of soil creation is pedogenesis. Pedon is a Greek word meaning "soil." Pedogenesis occurs when wind, ice or rain combine to scour mountains, hills and plains. Particles ranging in size from microscopic grains of sand to boulders large enough to qualify as hills themselves are washed into rivers and streams or blown into the air. Once it settles, this non-living matter combines with organic debris, including dead and dying plants, animal flesh and bones, fungus and the excreted wastes of various living organisms, to form soil. The process of creating the inorganic components of soil can take centuries to complete.
There are several types of decomposers. Scavengers include flies, cockroaches, wasps, earthworms, catfish, hyenas, opposums, turkey vultures, alligators, dung beetles and crayfish, as well as many other birds, insects and animals. Scavengers eat dead plants and animals, which speeds decomposition. Decomposition is the process of converting living material back into the essential minerals which allow life to exist. Some animals, such as dung beetles, exist specifically to convert the waste products of other animals back into soil. Earthworms perform the same task for plants, breaking them down and returning them to the environment in the form of rich, black castings.
Worm farming, or vermiculture, is the deliberate use of worms to decompose paper products, grass clippings, tree prunings, vegetable and fruit peelings, coffee grounds and tea leaves into soil. According to Mary Appelhof, author of "Worms Eat My Garbage," 2 lbs. of worms can eat 1 lb. of food every 24 hours. Your worms will produce 7 cubic feet of castings every four to six months. Worm castings are rich in nitrogen, phosphorus and other vital chemicals and minerals.
Efforts to speed the soil creation process would be useless if not combined with soil conservation. Soil conservation includes no-till farming methods, contouring and terracing of croplands and planting rain gardens, which are shallow depressions planted with mulched shrubs and grasses.
No-till farmers plant crops in a shallow, 1- to 3-inch deep groove in the soil instead of the traditional 12- to 18-inch deep till used in the late 1800s. Cover crops, such as crown vetch, soy beans and other legumes, help hold soil in place while the main crop grows. The waste plant material can be used as animal feed or as fuel for other farm production operations.
Storm water runoff carries large amounts of suspended soil for great distances. The abrasive action of the particles in the water, as well as of pebbles, stones and boulders, digs stream beds deeper, carrying away even more soil and sand. The farther runoff travels, the more damage it can do. Eventually, as the waters reach a level area and the flow slows, particles begin to settle, beginning with the largest boulders. This settling eventually creates deltas, areas of rich soil deposited by a slowing stream just before it enters the ocean. These deltas can alter the course of a given waterway, raising the water level and leading to extensive seasonal flooding.
Rain gardens planted far upstream can dramatically reduce the amount of debris carried downstream. Rain gardens trap soil and debris before it can enter waterways by slowing the flow of water. This prevents the loss of valuable topsoil and agricultural productivity. Topsoil loss leads to a need to amend local soil using organic and chemical fertilizers. Incomplete absorption of these soil amendments leads to agricultural runoff being swept into waterways, creating a vicious cycle. The nutrients in this runoff robs waterways of oxygen-carrying capacity and can lead to massive fish kills.