2 What is Soil? Soil – What is it? Unconsolidated porous mediaCompromised of inorganic (clay minerals and oxides) and organic components (organic matter)Has distinct physical, chemical, and biological propertiesSoil is dynamic – modified over time by physical, chemical, and biological agents
3 Midwest Agricultural Soils Typically fertile, but poorly drainedDrainage is often facilitated by networks of artificial, subsurface drains to enhance productivityabout 1 m below the soil surfacecan rapidly move excessive water (and soluble contaminants) to surface waterways
4 Sediment Movement Benefits of soil movement Nourishes floodplainsCreates deltas and islandsReplenishes wetlandsProblems with soil movementLoss of excessive amounts of fertile soilDecreases the depth of streams, rivers, lakes and reservoirsThis can increase water temperature, effecting aquatic speciesRequires increased water purificationPlusses – nourishes floodplain farm fields, creates deltas and islands, and replenishes wetlands.Minuses – loss of excessive amounts of soil from cropland, urban construction sites, logging, etc. due to greatly increased erosion, soil fills lakes and reservoirs, obstructs shipping channels, clogs hydroelectric turbines, and requires more purification of water.
5 ErosionErosion: 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 elsewhereThe cost of water and wind erosion in the U.S. is estimated in billions of dollars each yearreduced productivitysoil pollution of water and airSoil erosion is a global problem
6 Organic MatterOrganic matter (OM) improves soil productivity through physical, chemical, and biological actionsOrganic matter is a small fraction (2% to 4%) of soil -- mainly present on the soil surfaceErosion gradually depletes organic matter which decreases soil productivity
7 Effects of a Loss of Organic Matter Soils tend to lose their physical structure hard, compacted and cloddySoil aeration (water-holding capacity and permeability) decreasesLess oxygen available for plant roots to growLess water available for healthy plant growthLess water can soak into low permeability soils so run-off increasesBeneficial organisms are decreasedSuppress disease and break down organic residuesDo not function well at low soil oxygen and water levelsReduces soil nutrient storage and supply ability
8 Impacts of Erosion on Air Quality Soil particles blown by the wind into the air have a major impact on human and animal healthParticles suspended in air by wind are easily inhaled and accumulate in lung tissues causing major respiratory problemsConcentrated levels of wind blown particles can also reduce visibility and increase the risk of automobile accidentsThe Dust Bowl or the Dirty Thirties was a period of severe dust storms causing major ecological and agricultural damage to American and Canadian prairie lands from 1930 to 1936 (in some areas until 1940). The phenomenon was caused by severe drought coupled with decades of extensive farming without crop rotation, fallow fields, cover crops or other techniques to prevent erosion. Deep plowing of the virgin topsoil of the Great Plains had 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, with no natural anchors to keep the soil in place, it 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.[2
9 Factors Contributing to Soil Erosion List all the factors that you can think of that contribute to:Soil Erosion by WaterSoil Erosion by Wind
10 Factors Contributing to Soil Erosion Water erosionWind ErosionClimateSoil properties (aggregation/soil moisture)Soil coverLand managementTopographySoil surface roughnessUnsheltered distanceWind velocity and turbulence
11 The Dust Bowl A period of severe dust storms Caused major ecological and agricultural damageAffected American and Canadian prairie lands1930 to 1936 (in some areas until 1940)
12 The Dust BowlCausesSevere droughtDecades of extensive farming without conservation to prevent erosionDeep plowing of the virgin topsoil of the Great Plainsdisplaced the natural grasses that normally kept the soil in place and trapped moisture even during periods of drought and high windsDuring the drought of the 1930s, soil dried, turned to dust, and blew away eastward and southward in large dark clouds
13 The Dust BowlAt 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 OceanThese immense dust storms—given names such as "Black Blizzards" and "Black Rollers"—often reduced visibility to a few feetThe Dust Bowl affected 100,000,000 acres, centered on the panhandles of Texas and Oklahoma, and adjacent parts of New Mexico, Colorado, and Kansas
14 Reducing Soil Loss What are we currently doing to reduce soil loss? Have we had any dust storms recently?
15 Wisconsin Dust StormA massive dust storm that swept through central Wisconsin in late May, 2012Causes:Partially the result of an increase in exposed cropland in the region due to increased cultivation of the central sands regionThe number of acres of cultivated cropland increased by almost 42 percent from 2005 to 2011
16 2012 DroughtThe severe drought that hit the Farm Belt did not create another Dust Bowl or widespread crop failureExpected average national yields in 2012 would have been records in 1991Soil conservation mostly controlled erosion, despite record heat and lack of rain in June and JulyOther reasons for reduced erosionImproved seed qualityImproved planting practicesImproved farming technology
26 Reading AssignmentNew Conservation Program Protest Most Highly Erodible CroplandsGullies in Long-term No-till Fields can be TroublesomeThe Fate of Our Nation's Soil ResourceLinked on Assignment webpage“Due” Wednesday, Sept. 11