13.6 Soil Profile The soil profile is a series of horizontal layers of different chemical composition, physical properties, particle size, and amount of organic matter. Each recognizable layer of the profile is known as a horizon.

13.6 Soil Profile O horizon is made of litter, undecomposed or partially decomposed organic material. A horizon is the topsoil, or the uppermost layer. It contains most of the soil nutrients and living organisms. E horizon is formed from leaching darker materials. Usually very nutrient poor.

13.6 Soil Profile B horizon is the subsoil. It contains less organic matter and fewer organisms, but accumulates nutrients leached from topsoil. It is poorly developed in dry areas. C horizon is weathered parent material. R horizon is bedrock.

13.6 Soil Profile

13.6 Soil Profile Over 15,000 separate soil types have been classified in North America. Most cultivated land can be classified as either grassland or forest soil. Grassland soils usually have a deep topsoil layer. A lack of leaching results in a thin layer of subsoil. In forest soils, which are typically high rainfall areas, the topsoil layer is relatively thin, but topsoil leachate forms a subsoil that supports substantial root growth.

13.6 Soil Profile Major soil types

13.7 Soil Erosion Erosion is the wearing away and transportation of soil by wind, water, or ice. Worldwide, erosion removes 25.4 billion metric tons of soil per year. Made worse by deforestation and desertification. Poor agricultural practices increase erosion and lead to the transport of associated fertilizers and pesticides.

13.7 Soil Erosion Most current agricultural practices lose soil faster than it can be replenished. Wind erosion may not be as evident as water erosion, but is still serious. It is most common in dry, treeless areas. Great Plains of North America have had four serious bouts of wind erosion since European settlement in the 1800s.

13.7 Soil Erosion Worldwide soil erosion

13.8 Soil Conservation Practices Agricultural Potential Worldwide: 11% of land surface is suitable for crops. An additional 24% is in permanent pasture. United States: 20% land surface suitable for crops. 25% in permanent pasture. African Continent: 6% land surface suitable for crops. 29% can be used for pasture.

13.8 Soil Conservation Practices Soil Quality Management Components: Enhance organic matter. Avoid excessive tillage. Manage pests and nutrients efficiently. Prevent soil compaction. Keep the ground covered. Diversify cropping systems.

13.8 Soil Conservation Practices Contour farming is tilling at right angles to the slope of the land. Each ridge acts as a small dam. Useful on gentle slopes. One of the simplest methods for preventing soil erosion. Strip farming is the practice of alternating strips of closely sown crops to slow water flow, and increase water absorption.

13.8 Soil Conservation Practices Terracing is the practice of constructing level areas at right angles to the slope to retain water. Good for very steep land. Terraces

13.8 Soil Conservation Practices Waterways are depressions in sloping land where water collects and flows off the land. Channels movement of water. Windbreaks are plantings of trees or other plants that protect bare soil from full force of the wind. Windbreaks reduce wind velocity, decreasing the amount of soil that can be carried.