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Ag I Soils

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Differentiate between natural soil erosion and soil erosion caused by humans List the main causes of accelerated erosion List and define the major types of soil erosion

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Natural process that occurs all the time Part of the soil formation process Much slower than soil formation

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A speed up of the normal rate of erosion Begins when lands natural plant cover is removed Caused by two basic forces-moving water and wind

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Occurs when raindrops strike the earth Raindrops hit at about 20 MPH If raindrops strike plants their force is broken and they become harmless If raindrops strike bare soil the force is absorbed by soil particles and they are torn apart When this happens the soil particles are either suspended and carried away or filter into soil pore spaces making the soil less permeable.

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Most destructive action of water on soil The faster the water flows the more destructive it becomes Three-fold damage Existing soil structure is damaged Soil surface is reshaped making it less workable Soil is carried away and may eventually be redeposited elsewhere Silt deposits can sometimes be good Nile Valley, Mississippi Delta Most are harmful causing clogged waterways, fish kills, filled lakes, muddy streams and mud flats

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2 basic actions-drying and dislodging, movement A serious problem in dry areas where the land is relatively flat with few trees

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Dries the soil surface Moves soil particles leaving behind larger sand particles making soil surfaces become very sandy or covered by a layer of clay

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Gradual and fairly uniform removal of the surface soil Occurs slowly so producer may not even be aware it is taking place Caused by splash erosion coupled with a slow runoff of soil-laden water

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Gradual reduction of the topsoil thickness This leads to a decrease in soil productivity and eventually totally unproductive soil Also notice color changes in the soil in plowed fields because as they are plowed subsoil is brought to the top Discoloration is a indication that sheet erosion is well advanced and damage has already been done

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More rapid and visible Rills are small streams cut into the soil surface by running water Damage has occurred when rills appear May be very small or large and noticeable When rills become too large they become a gully

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Obvious Severe problem More obvious than rill or sheet erosion

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2 forms of damage Soil removal Sand deposits or drifts

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Much like sheet erosion Wind simply picks up the soil particles and blows them away As soil blows away The field becomes less productive It retains less rainwater It produces less vegetation Damage may be severe before it becomes obvious

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More obvious Result when the wind is forced to change directions abruptly Fencerows, windbreaks, sides of buildings When the wind changes direction it redeposit's the soil particles Larger and more flat bare fields are the more likely they will be affected by wind erosion

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