Soil conservation
Soil conservation refers to a range of agricultural practices aimed at maintaining soil quality and preventing erosion. These practices are essential as they help reduce soil degradation, which affects agricultural productivity and contributes to environmental issues such as air and water pollution. As of 2021, it was reported that up to 40 percent of Earth's usable land had experienced degradation, impacting food security globally. Soil conservation efforts include methods such as using vegetative cover to protect soil, minimizing tillage, and implementing crop rotation systems. Techniques like no-till and mulch-till planting help maintain soil structure by reducing exposure to wind and rain. Additionally, establishing windbreaks with trees or shrubs and creating buffer zones along waterways can further protect soil from erosion and improve water quality. Historical events, such as the Dust Bowl in the 1930s, highlight the critical need for effective soil conservation measures. Overall, these strategies are vital for sustainable agriculture and the health of ecosystems, addressing both current land challenges and future food security.
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Soil conservation
DEFINITION: Use of agricultural and other cultivation practices aimed at maintaining soil quality and reducing erosion
By using agricultural methods that protect soil from degradation, farmers can reduce soil erosion, prevent soil particles from contributing to air and water pollution, and improve crop production.
According to the United Nations Environment Programme, by 2021 up to 40 percent of Earth’s usable land was degraded, a situation that poses a threat to agricultural production around the world. The introduction of minerals, metals, nutrients, fertilizers, pesticides, bacteria, and pathogens suspended in topsoil into waterways is a significant source of water pollution and is a threat to fisheries, wildlife habitats, and drinking-water supplies. The introduction of soil particles into the air through wind is a significant source of air pollution. Soil conservation is the effort by farmers and other land users to prevent the loss of topsoil from wind erosion, water erosion, desertification, and chemical deterioration such as the buildup of salts and fertilizer acids.
The Industrial Revolution of the nineteenth century and the explosion of the twentieth century encouraged people to till new land, cut down forests, and disturb soil for the expansion of towns and cities. The newly exposed topsoil quickly succumbed to erosion from rainfall, floods, wind, ice, and snow. The Dust Bowl, which occurred in the Great Plains in the United States during the 1930s, is one example of the devastating effects of wind erosion.
Hugh Hammond Bennett, often called the father of soil conservation, lobbied for congressional establishment of the Soil Erosion Service, which was formed in the US Department of the Interior in 1933, and the establishment of voluntary Soil Conservation Districts in each state. Bennett was named the first chief of the renamed Soil Conservation Service, now part of the Department of Agriculture, in 1937 (in 1994 the name of the agency changed again, to the Natural Resources Conservation Service). On August 4, 1937, the Brown Creek Conservation District in Bennett’s home county, Anson County, North Carolina, became the first Soil Conservation District in the United States. Local landowners voted to establish the district by three hundred to one, proving that farmers were concerned about soil conservation. A reporter for the Charlotte Observer newspaper sought out the one negative voter, and after the program was explained to him, he changed his opinion. By 1948 more than 2,100 districts had been established nationwide; this number grew to 3,000 by 2012. The districts were eventually renamed Soil and Water Conservation Districts.
The Food Security Act of 1985 authorized the Conservation Reserve Program to take out of production any land deemed to be highly susceptible to erosion; it also required farmers to develop soil conservation plans for any remaining susceptible land. The Natural Resources Conservation Service estimated that with such soil conservation measures, the loss of topsoil in the United States was cut nearly in half, reduced from 1.6 billion tons per year to 0.9 billion tons. The European Community and Australia also adopted soil conservation measures during the 1990s.
Soil conservation practices include covering the soil with vegetation, reducing soil on tilled land, creating wind and water barriers, and installing buffers. Vegetative cover slows the wind at ground level, slows water runoff, protects soil particles from being detached, and traps blowing or floating soil particles, chemicals, and nutrients. Because the greatest wind and water erosion damage often occurs during seasons in which no crops are growing or natural vegetation is dormant, soil conservation often depends on permitting the dead residues and standing stubble of the previous crop to remain in place until the next planting time. In forested areas, annual tree foliage loss serves as a natural ground mulch. Farmers can also reduce erosion by planting grass or legume cover crops until the next planting season for their primary crops or as part of a crop rotation cycle or no-till planting system.
Modern no-till and mulch-till planting systems reduce soil exposure to wind and rain. No-till systems leave the soil cover undisturbed before planting; crop seeds are inserted into the ground through narrow slots in the soil. In mulch-till planting, a high percentage of the dead residues of previous crops are retained on the soil’s surface when a new crop is planted.
The ways in which crops are planted can also help to reduce erosion. Row crops can be planted at right angles to the prevailing winds and to the slope of the land in order to absorb wind and rainwater runoff energy and trap moving soil particles. Crops may be planted in small fields to prevent the avalanches caused by an increase in the amount of soil particles transported by wind or water as the distance across bare soil increases. As the amount of soil moved by wind or water increases, the erosive effects of the wind and water also increase. Smaller fields reduce the length and width of unprotected areas of soil.
Wind and water barriers include tree plantings and crosswind strips of perennial shrubs and tall grasses, which act as windbreaks, slowing wind speeds at the surface of the soil. The areas protected by such windbreaks extend for ten times the height of the barriers. In alley cropping, which is used in areas of sustained high winds, crops are planted between rows of larger mature trees. Contour strip farming on slopes, planting grass waterways in areas where rainwater runoff concentrates, and planting grass field borders 3 meters (10 feet) wide on all edges of cultivated or disturbed soil are additional methods for reducing wind speed and rainwater runoff and trapping soil particles, chemicals, and nutrients.
Soil conservation buffers work to filter agricultural runoff to remove and chemicals. Riparian buffers are waterside plantings of trees, shrubs, and grasses, usually 6 meters (20 feet) in width. Riparian buffers planted only in grass are called filter strips. Grassed waterways, field borders, water containment ponds, and contour grass strips are other types of soil conservation buffers.
Bibliography
Blanco, Humberto, and Rattan Lal. Principles of Soil Conservation and Management. New York: Springer, 2008.
Cherlinka, Vasyl. "Soil Conservation Methods and Benefits of Implementation." EOS Data Analytics, 26 Apr. 2023, eos.com/blog/soil-conservation/. Accessed 23 July 2024.
Field, Harry L., and John B. Solie. “Erosion and Erosion Control.” In Introduction to Agricultural Engineering Technology: A Problem Solving Approach. 3d ed. New York: Springer, 2007.
"Global Hotspots for Soil Conservation Are Poorly Detected." Phys.org, 22 Oct. 2022, phys.org/news/2022-10-global-hotspots-soil-poorly.html. Accessed 23 July 2024. Plaster, Edward. Soil Science and Management. 5th ed. Clifton Park, N.Y.: Delmar, 2008.
Schwab, Glen, et al. Soil and Water Conservation Engineering. 5th ed. Clifton Park, N.Y.: Delmar, 2005.