Soil Erosion

Soil ErosionAg ISoils

ObjectivesDifferentiate between natural soil erosion and soil erosion caused by humansList the main causes of accelerated erosionList and define the major types of soil erosionGeological ErosionNatural process that occurs all the timePart of the soil formation processMuch slower than soil formation

Accelerated ErosionA speed up of the normal rate of erosionBegins when lands natural plant cover is removedCaused by two basic forces-moving water and wind

Water-Caused Erosion

Splash ErosionOccurs when raindrops strike the earthRaindrops hit at about 20 MPHIf raindrops strike plants their force is broken and they become harmlessIf raindrops strike bare soil the force is absorbed by soil particles and they are torn apartWhen this happens the soil particles are either suspended and carried away or filter into soil pore spaces making the soil less permeable.

Run-offMost destructive action of water on soilThe faster the water flows the more destructive it becomesThree-fold damageExisting soil structure is damagedSoil surface is reshaped making it less workableSoil is carried away and may eventually be redeposited elsewhereSilt deposits can sometimes be good Nile Valley, Mississippi DeltaMost are harmful causing clogged waterways, fish kills, filled lakes, muddy streams and mud flatsRun-off

Wind ErosionWind Erosion2 basic actions-drying and dislodging, movementA serious problem in dry areas where the land is relatively flat with few trees

Wind ActionDries the soil surfaceMoves soil particles leaving behind larger sand particles making soil surfaces become very sandy or covered by a layer of clayResults of ErosionSheet ErosionGradual and fairly uniform removal of the surface soilOccurs slowly so producer may not even be aware it is taking placeCaused by splash erosion coupled with a slow runoff of soil-laden waterResults of Sheet ErosionGradual reduction of the topsoil thicknessThis leads to a decrease in soil productivity and eventually totally unproductive soilAlso notice color changes in the soil in plowed fields because as they are plowed subsoil is brought to the topDiscoloration is a indication that sheet erosion is well advanced and damage has already been done

Sheet Erosion

Rill ErosionMore rapid and visibleRills are small streams cut into the soil surface by running waterDamage has occurred when rills appearMay be very small or large and noticeableWhen rills become too large they become a gullyRill Erosion

Gully ErosionObviousSevere problemMore obvious than rill or sheet erosionGully Erosion

Sand blows2 forms of damageSoil removalSand deposits or driftsSand blows-Soil RemovalMuch like sheet erosionWind simply picks up the soil particles and blows them awayAs soil blows away The field becomes less productiveIt retains less rainwaterIt produces less vegetationDamage may be severe before it becomes obvious

Sand blow

Sand blows-Deposits or DriftsMore obviousResult when the wind is forced to change directions abruptlyFencerows, windbreaks, sides of buildingsWhen the wind changes direction it redeposit's the soil particlesLarger and more flat bare fields are the more likely they will be affected by wind erosionSand blows-Drifts

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