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September 24, 2012

» Soil – What is it? ˃Unconsolidated porous media ˃Compromised of inorganic (clay minerals and oxides) and organic components (organic matter) ˃Has distinct physical, chemical, and biological properties » Soil is dynamic – modified over time by physical, chemical, and biological agents

» Typically fertile, but poorly drained » Drainage is often facilitated by networks of artificial, subsurface drains to enhance productivity ˃about 1 m below the soil surface ˃can rapidly move excessive water (and soluble contaminants) to surface waterways » Preferential flow paths to tile drain systems develop reducing the effects of soil transport

» Benefits of soil movement ˃Nourishes floodplains ˃Creates deltas and islands ˃Replenishes wetlands » Problems with soil movement ˃Loss of excessive amounts of fertile soil ˃Decreases the depth of streams, rivers, lakes and reservoirs +This can increase water temperature, effecting aquatic species ˃Requires increased water purification

» Erosion - the wearing away of the land surface by rain or irrigation water, wind, ice or other agents that abrade, detach and remove soil from one point on the earth's surface and deposit it elsewhere. » In the U.S., the cost of water and wind erosion each year is estimated in billions of dollars, because of the loss of the upper soil layer causing reduced productivity and soil pollution of water and air. » Soil erosion is a global problem. Erosion of soil can contribute to instability in a region because of inability to produce adequate food and fiber.

» Organic matter (OM) contributes to soil productivity through its effect on the physical, chemical, and biological properties of the soil. » Organic matter is a small fraction (2% to 4%) of soil -- mainly present on the soil surface. » Erosion gradually depletes organic matter and decreases soil productivity.

» Soils tend to lose their physical structure. This makes the soil hard, compacted and cloddy. » Soil aeration (water-holding capacity and permeability) are decreased. Decreased aeration means less oxygen available for plant roots to grow and less water available for healthy plant growth. When soil permeability decreases, less water will soak into the soil and more will run-off. » Beneficial organisms that suppress disease and break down organic residues will not function well due to reduced oxygen and water in soil. This in turn will reduce nutrient storage and supply abilities of the soil.

» Soil particles blown by the wind into the air have a major impact on human and animal health. » Particles suspended in air by wind are easily inhaled and accumulate in lung tissues causing major respiratory problems. » Concentrated levels of wind blown particles can also reduce visibility and increase the risk of automobile accidents.

» A period of severe dust storms » Caused major ecological and agricultural damage » Affected American and Canadian prairie lands » 1930 to 1936 (in some areas until 1940)

» Causes ˃Severe drought ˃Decades of extensive farming without conservation to prevent erosion ˃Deep plowing of the virgin topsoil of the Great Plains which displaced the natural grasses that normally kept the soil in place and trapped moisture even during periods of drought and high winds. » During the drought of the 1930s, soil dried, turned to dust, and blew away eastward and southward in large dark clouds.

» At times the clouds blackened the sky reaching all the way to East Coast cities such as New York and Washington, D.C. » Much of the soil ended up deposited in the Atlantic Ocean, carried by prevailing winds which were in part created by the dry and bare soil conditions itself. » These immense dust storms—given names such as "Black Blizzards" and "Black Rollers"—often reduced visibility to a few feet (around a meter). » The Dust Bowl affected 100,000,000 acres (400,000 km2), centered on the panhandles of Texas and Oklahoma, and adjacent parts of New Mexico, Colorado, and Kansas.

» Did you see dust storms this summer? » What conservation practices are we using now to keep soil on the farm?

» List all the factors that you can think of that contribute to: Soil Erosion by WaterSoil Erosion by Wind

» A tillage system that buries residue and pulverizes soil leads to high erosion risk » A tillage system that preserves surface residue and minimizes soil disturbance reduces erosion

» Conventional tillage creates soil disturbance and mixing » Conservation tillage reduces soil disturbance to a minimum and keeps more residue from the previous crop at the soil surface

» Contour planting » Strip cropping » Contour strip cropping » Grassed waterways

» Wisconsin, the Center for Land Use Education: ˃A massive dust storm that swept through central Wisconsin in late May ˃Partially the result of an increase in exposed cropland in the region ˃The number of acres of cultivated cropland in the central sands region increased by almost 42 percent from 2005 to 2011

» The severe drought that has hit the Farm Belt does not immediately threaten to create another Dust Bowl or widespread crop failure » Thanks to rapid innovations in the past 20 years: ˃seed quality ˃planting practices ˃farming technology » Expected average national yields this year would have been records in 1991, and soil conservation is generally holding land in place despite record heat and lack of rain in June and July. » USA Today

» Documentary by Ken Burns Documentary » Starts Sunday, November 18, 2012 ˃Only on PBS