Tillage
TILLAGE
TILLAGE. Farmers perform tillage when they prepare soil for the raising of crops. Soil tillage has three primary purposes. Prior to planting, farmers use tillage to mix compost, manure, and other fertilizers into the root zone where growing plant roots may reach it. Tillage also aids seed germination by creating a smooth, uniform soil surface for planting. After planting, farmers use tillage to control weeds between crop plants—including vegetable, fruit, forest, medicinal, and farm crops. Since early agriculture, tillage has been the first step in the process that makes it possible to harvest food from plants. However, soil tillage has come under close scrutiny since soil is recognized as a natural resource that deserves protection. Agronomists (scientists who study crop production and soil management) are concerned because erosion (soil loss) from tillage is one of the most significant problems in agriculture. If left unchecked, soil erosion leads to loss of soil productivity, as well as off-site deposition of sediments and farm chemicals that pollute surface and groundwater.
Early History of Tillage
Soil tillage had its beginnings ten to twelve millennia ago in the Near East, as early farmers used a digging stick to loosen the soil before planting seeds. The tool evolved from digging stick to spade to triangular blade, and was made of wood, stone, and ultimately metal. One or more people likely used their bodies to pull the first wooden plows. Animals began pulling plows around 3000 B.C.E. in Mesopotamia. Jethro Tull (1674–1741), a pioneering British soil physicist, was the first to recognize that loosening soil helps to supply plant roots with nutrients.
In North America, agricultural innovators copied European trends. Charles Newbold patented the first cast-iron plow in the late 1700s. In 1837, John Deere and Leonard Andrus began manufacturing steel plows. By the 1840s, the growing use of manufactured equipment had increased the farmers' need for cash, thus encouraging the rise of commercial farming. Agriculture, society, and economics were closely linked, as George Marsh said in an address delivered in 1847 to the Agricultural Society of Rutland County, Vermont: "Pure pastoral life, as I have said, advances man to but an humble stage of civilization, but when it is merged in agriculture, and the regular tillage of the soil commences, he is brought under the dominion of new influences, and the whole economy of domestic and social life is completely revolutionized." Marsh explained that once cultivation of soil begins, all aspects of society are affected by changes: "Hence arises the necessity of fixed habitations and store houses, and of laws which shall recognize and protect private exclusive right to determinate portions of the common earth, and sanction and regulate the right of inheritance, and the power of alienation and devise, in short the whole frame work of civil society."
Horses and mules had taken over the work of draft oxen by the late 1800s. As agriculture became increasingly mechanized and commercialized, tractors became more common and replaced most draft animals by the early to mid-1900s. Until then, the size of most family farms was restricted to the land that a man could work using several horses. With the advent of the light, gasoline-powered tractor, both family and commercial farms added crop area and prospered.
The Dust Bowl
Tractors helped to create farm fields that stretched far westward, setting the stage for the Dust Bowl in the 1930s. Open grassland in the southwestern Great Plains region of the United States was settled and farmed by homesteaders who planted row crops and grazed their cattle. Before farmers came, the region was covered by hardy grasses that held the soil in place despite long droughts and torrential rains. Tillage combined with drought left the soil exposed to wind erosion. Lightweight soil components—organic matter, clay, and silt—were carried great distances by the winds, while sand and heavier materials drifted against houses, fences, and barns. This drifting debris buried farm buildings and darkened the sky as far as the Atlantic coast. Over a period of ten years, millions of acres of farmland became useless, and hundreds of thousands of people were forced to leave their homes.
The Dust Bowl gave impetus to the soil conservation movement; nevertheless, mechanization continued to spread. In 1938, Hugh Bennett and Walter Lowder-milk of the United States Soil Conservation Service wrote in the Yearbook of Agriculture : "Soil erosion is as old as farming. It began when the first heavy rain struck the first furrow turned by a crude implement of tillage in the hands of prehistoric man. It has been going on ever since, wherever man's culture of the earth has bared the soil to rain and wind."
Conservation Tillage and Sustainable Agriculture
By 1954, the number of tractors on farms exceeded the number of horses and mules for the first time. The increasing availability of agricultural chemicals in the midto late-1900s, including weed killers that did not harm crop plants, further changed crop and soil management practices. "Conservation tillage"—a broad spectrum of farming methods that help to reduce soil erosion due to wind and water and help to reduce labor and fuel—gained a following among farmers in the 1980s. Early methods of conservation tillage, such as no-tillage, were un sustainable since they relied heavily on chemical weed killers called herbicides. The no-tillage method worked well to control both soil erosion and weeds, while requiring less energy. However, herbicides were highly toxic to people and wildlife and their manufacture and use caused environmental pollution. Tillage reduction methods were fine-tuned to suit local conditions throughout the United States.
By 1989, a far-sighted handful of new-generation farmers became interested in lowering costs, avoiding agricultural chemicals, and saving soil. They started the agricultural movement that became known as "sustainable agriculture." Low-input methods meet the needs of more farmers each year. They are promoted by a program of the United States Department of Agriculture called Sustainable Agriculture Research and Education (SARE). Farmers practicing sustainable agriculture produce food and fiber while enhancing environmental quality and natural resources, make the most efficient use of nonrenewable resources and on-farm resources. Further, they integrate natural biological cycles and pest controls and sustain the economic viability of farm operations.
Today's tillage practices reflect society's concern with environmental quality, and the farmer's need to reduce costs while preventing soil erosion and compaction. However, significant amounts of soil are still lost annually around the world where soil is not protected.
See also Agronomy ; Greenhouse Horticulture ; Horticulture ; Organic Farming and Gardening ; Sustainable Agriculture .
BIBLIOGRAPHY
Blann, K., review of Coughenour, C. M., and S. Chamala, "Conservation Tillage and Cropping Innovation: Constructing the New Culture of Agriculture," in Conservation Ecology 5 (2): 2 (2001). Ames: Iowa State University Press.
Hillel, Daniel. Environmental Soil Physics. San Diego: Academic Press, 1998.
Jasa, P. J., D. P. Shelton, A. J. Jones, and E. C. Dickey. Conservation Tillage and Planting Systems. Bulletin G91-1046. Lincoln, Neb.: Cooperative Extension, Institute of Agriculture and Natural Resources, University of Nebraska, Lincoln, 1997.
Library of Congress. The Evolution of the Conservation Movement 1850–1920. Library of Congress: Washington, D.C.
Robinson, Clay. Dr. Dirt. Online notes for courses in soil science. Canyon, Tex.: West Texas A&M University.
United States Department of Agriculture, Economic Research Service. A History of American Agriculture 1776–1990. Washington, D.C.: U.S. Government Printing Office, n.d.
Patricia S. Michalak
tillage
till·age / ˈtilij/ • n. the preparation of land for growing crops. ∎ land under cultivation: forty acres of tillage.