Soil Conservation

Human activities have caused increases of soil erosion since the beginning of agriculture more than 5,000 years ago. Plentiful land and a scarcity of labor in some countries encouraged farmers to "wear out" a piece of land, abandon it, and then move on to more fertile ground. This practice is still common in some developing countries, in the form of shifting cultivation or "slash and burn." This involves farmers cutting down an area of forest, burning the downed vegetation, and planting their crops among the ashes. After several years, the farmer moves to another area of forest and repeats the process. Although shifting cultivation is commonly considered to be a major cause of soil erosion, if sufficient time is allowed between clearings, soil fertility can maintain itself over the longer term.

Practices to protect the land from erosion have existed for several thousand years, particularly in the tropics and subtropics. For example, Chinese artifacts dating from about 4,500 years ago (2500 B.C.) depict terraces used to control erosion on cultivated slopes. Similarly, terraces have been used to grow rice in the Philippines for more than 1,000 years.

In the United States, abusive agricultural practices in combination with drought caused the great dust-storms of 1934 and 1935, which carried huge quantities of soil from the Great Plains to the Atlantic Ocean. Soil conservation became a practice of national importance as a result of those storms. President Franklin Roosevelt signed bills in 1935 that established the Soil Conservation Service, an agency responsible for implementing practices to control soil erosion. Individual states also passed laws establishing nearly 3,000 local soil conservation districts.

For the next several decades, U.S. farmers produced consistent surpluses of agricultural commodities. They had little incentive to push the land for higher yields. However, in the 1970s grain exports increased, especially to the Soviet Union. Farmers were encouraged to cultivate marginal lands to fill the export quotas. Those areas, amounting to almost two million acres (800,000 hectares), included land on slopes and wetter areas that are relatively vulnerable to erosion.

The concern of the environmental movement about water quality in the 1970s helped to return attention to the problem of soil erosion. Excessive amounts of phosphorus and nitrogen occurred in streams and lakes as result of agricultural fertilization practices, and this added to public criticism of soil conservation programs. Congress passed the Soil and Water Resource Conservation Act to evaluate and conserve soil, water, and related resources on non-federal land.

The 1985 Food Security Act encouraged land management practices that were intended to reduce soil erosion. The Act removed up to 45 million acres (18 million hectares) of highly erosion-prone land from intensive cultivation. It also prevented the conversion of rangelands into cultivated fields through its "sodbuster" provision. The Act withdrew some commodity (feed grain, wheat, rice, upland cotton, etc.) acreage from production, through multiyear acreage set-asides and conservation easements. It also required farmers to develop plans and apply management practices that would keep soil erosion on highly erodible lands within acceptable limits.