1. Agricultural Soils
September 9, 2013

2. What is Soil? 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

3. Midwest Agricultural Soils
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

4. Sediment Movement 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
Plusses – 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. Erosion
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
The cost of water and wind erosion in the U.S. is estimated in billions of dollars each year
reduced productivity
soil pollution of water and air
Soil erosion is a global problem

6. Organic Matter
Organic matter (OM) improves soil productivity through physical, chemical, and biological actions
Organic matter is a small fraction (2% to 4%) of soil -- mainly present on the soil surface
Erosion 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 cloddy
Soil aeration (water-holding capacity and permeability) decreases
Less oxygen available for plant roots to grow
Less water available for healthy plant growth
Less water can soak into low permeability soils so run-off increases
Beneficial organisms are decreased
Suppress disease and break down organic residues
Do not function well at low soil oxygen and water levels
Reduces 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 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
The 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.[1] 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 Water
Soil Erosion by Wind

10. Factors Contributing to Soil Erosion
Water erosion
Wind Erosion
Climate
Soil properties (aggregation/soil moisture)
Soil cover
Land management
Topography
Soil surface roughness
Unsheltered distance
Wind velocity and turbulence

11. The Dust Bowl 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)

12. The Dust Bowl
Causes
Severe drought
Decades of extensive farming without conservation to prevent erosion
Deep plowing of the virgin topsoil of the Great Plains
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

13. The Dust Bowl
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
These immense dust storms—given names such as "Black Blizzards" and "Black Rollers"—often reduced visibility to a few feet
The 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 Storm
A massive dust storm that swept through central Wisconsin in late May, 2012
Causes:
Partially the result of an increase in exposed cropland in the region due to increased cultivation of the central sands region
The number of acres of cultivated cropland increased by almost 42 percent from 2005 to 2011

16. 2012 Drought
The severe drought that hit the Farm Belt did not create another Dust Bowl or widespread crop failure
Expected average national yields in 2012 would have been records in 1991
Soil conservation mostly controlled erosion, despite record heat and lack of rain in June and July
Other reasons for reduced erosion
Improved seed quality
Improved planting practices
Improved farming technology

17. Crop Residue

19. Tillage & Erosion
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

20. Tillage Practices
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

21. Conservation Practices
Contour planting
Strip cropping
Contour strip cropping
Grassed waterways

22. Contour Planting

23. Strip Cropping

24. Contour Strip Cropping

25. Grassed Waterways

26. Reading Assignment
New Conservation Program Protest Most Highly Erodible Croplands
Gullies in Long-term No-till Fields can be Troublesome
The Fate of Our Nation's Soil Resource
Linked on Assignment webpage
“Due” Wednesday, Sept. 11