For much of American history, farmers planted their crops in straight lines, which had been the standard practice in Europe since Roman times. During the Great Depression, America suffered a long drought. Winds during dust storms swept up the dry earth in the Great Plains, turning soil into more dust. This phenomenon became known as the Dust Bowl. It devastated agriculture, and it became impossible to live in much of the country. Scientists needed to find a way to ensure that America never suffered another Dust Bowl.
Adopting the Arc
Researchers found that one of the main causes of the Dust Bowl was soil erosion. In the 1920s, mechanical advancements in agricultural equipment enabled farmers to plow more land than ever before. This excessive plowing stripped away much of the fertile topsoil and left the land more vulnerable to drought. In addition, farms in the Midwest had always experienced problems with erosion by water. When water flows quickly down a hill, it picks up dirt, taking soil with it into rivers and streams. When the drought hit, the remaining soil became very dry. The slightest breeze could lift it into the air and blow it away. Scientists decided that planting the crops in straight lines was part of the problem.
They instructed the farmers to start planting their crops in arcs along the sides of hills. The arcs caught rainwater and kept it from washing the soil away, allowing more water to soak into the soil instead. Crops grew taller, and the soil was less dry. The practice of planting crops in curves along a hill is referred to as contour farming. Today, farmers in hilly regions of the United States, Canada, and Australia use contour farming to protect soil and to produce healthier crops.
See for yourself: http://www.youtube.com/watch?v=6x0qBVVy5ps
Contour farming only works in areas with rolling hills. In mountainous regions, farmers use terraces to beat erosion. Watch the video and check out the links below to learn how terraced farming works.