Sustainable agricultural practices and home organic gardeners do not use chemical methods to control weeds and fertilize plants. The University of California at Davis Sustainable Agriculture and Research Program describes sustainability as "the principle that we must meet the needs of the present without compromising the ability of future generations to meet their own needs." Organic practices ensure that soil will remain fertile and productive for future farmers.
Pre-emergent herbicide is a substance that kills plants as they germinate or in the beginning stages of root development. Organic pre-emergent herbicide kills weeds with materials derived exclusively from natural sources. Corn gluten meal is a natural product used as a pre-emergent herbicide. Discovered by Nick Christians, an Iowa State University horticulturist, in 1986, it is exempt from EPA testing because it is a completely natural product.
Research shows that 50 to 60 percent weed control can be achieved in the first year when corn gluten is applied at 20 lbs. per 1,000 square feet; 80 to 85 percent in the second year; and over 90 percent control by the third year, according to an Ohio State University Extension report on natural lawn care. The proteins in corn gluten inhibit the germination of weed seed and root development. Successful weed eradication depends on application in spring after the last frost and in autumn as weed seed heads mature.
Large-scale sustainable agriculture programs often recommend cover crops as a way to control weeds between crop and orchard rows. Cover crops such as clover, alfalfa and vetch suppress weeds, add nutrient content to soil and prevent erosion. The University of California Davis sustainability program holds educational seminars to help farmers transition from chemical herbicide use to planting cover crops.
Plants need 17 nutrients to grow well, according to Jerry Goodspeed, Utah State University horticulturist. Organic fertilizer supplies a range of nutrients because it is derived from all-natural sources, including animal manures, seaweed products, mined rock powders, fish waste, cottonseed meal, feathermeal and bone meal. Living organisms in soil ingest organic fertilizer materials and transform them into nutrients. Vegetable and fruit plant roots then absorb the nutrients and their nutritional content is increased.
Organic fertilizer enriches soil by providing food for earthworms, fungi, beneficial bacteria, protozoa, anthropods and nematodes that inhabit the soil food web. The soil food web is the community of living organisms within soil that "make it possible to have clean air, clean water, healthy plants and moderated water flow," according to the Natural Resources Conservation Service. Chemical fertilizers boost plant growth directly but do not feed the essential living organisms that populate soil.