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Transcript
Soil Erosion and Salinization Colm Parrish and Nathan Lampenfeld Soil Composition • Soil is made up of four layers or horizons – Leaf Litter (O Horizon) – Topsoil (A Horizon) – Subsoil (B Horizon) – Parent Soil (C Horizon) • Topsoil is the extremely fertile soil made up of partially decomposed organic matter and minerals Human Effects on Soil • Over the years, human farming has stripped the amount of topsoil on arable land • Over-plowing land can cause tillage erosion, which was one of the main factors that led to the Dust Bowl of the 1930s • There is currently insufficient data to show the effects of soil erosion on crop production • Soil erosion, the natural process, only becomes an issue when human activity speeds up the process Reason for Concern “One reason that soil erosion is not a high priority for many governments and farmers is that it usually occurs so slowly that its cumulative effects may take decades to become apparent. For example, the loss of 1 millimeter is so small it goes undetected. But over a 25year period the loss would be 25 millimeters, which would take about 500 years to replace by natural processes.” -David Pimentel The New Dust Bowl • In China, massive amounts of over plowing and over grazing is causing massive wind erosion • Creates huge plumes of dust – Reduces visibility in northeast Chinese cities – Causes visibility reduction and air pollution in Japan, Korea, and the Northwest United States Climate Change and Erosion • Climate change is bringing colder, or warmer, temperatures to soil. Soil moisture levels are very low at the surface of excessively drained soils or during periods of drought. This releases particles of soil to be carried away by wind. This effect also occurs in freeze-drying of the soil surface during winter months. • Climate change is also anticipated to have great effects on the water cycle, which directly effects soil erosion by water Desertification • The productive topsoil of arid or semiarid land falls by 10 percent due to human and natural causes – Prolonged drought – Reduction of topsoil due to human activities • According to the UN, about 40 percent of the world’s land is suffering from desertification Ways to Prevent Soil Erosion • There are various ways to prevent soil erosion – Windbreaks prevent wind erosion – Methods to prevent water erosion • • • • • Terracing Contour Farming Strip Cropping Alley cropping Gully reclamation • In order to regain topsoil, organic fertilizers such as manure and compost should be used The Importance of Plants • Locally indigenous plants are more efficient at creating roots in soil, holding the soil in place, than imported crops • Plants slow down the running off of water, allowing the soil to absorb it • Plants break te impact of rain on soil, slowing down erosion Salinization • Caused by irrigation, excess salts create a crust over topsoil • Waterlogging occurs when the plants are over watered, and the water table rises. The saline water then envelops the deep roots, killing the plant • Only way to treat salinization is flushing, underground drainage, or not growing on the land for several years