Soil erosion Flashcards
Problems with soil erosion
Erodes clay and organic matter with nutrients
Reduces pedon thickness, volume of soil providing water and nutrients to roots
Impeded machinery and animal movement
Increases pollution
What determined susceptibility?
Texture - silt sized particles
Structure - aggregation resists detachment and transport, stabilized by organic matter, Fe and Al oxides, clays
Slope
Erosion by water process
Rain drop detachment
Transport
Then Deposition
Overland flow
Favored by ponding, result of raindrops sealing soil surface, rainfall exceeding infiltration
Types of Erosion
Sheet - runoff in thin sheets
Rill - runoff in many small channels (rills), deeper
Gully - runoff in a single wide, deep channel
Universal Soil Loss Equation
A = RKLSCP
A - long term average annual soil loss for a location
R - long term average rainfall runoff erosivity factor
K - erodibility index (texture and structure)
L - slope length factor
S - slope angle factor
C - soil cover factor
P - erosion control practice factor
Degradation Control
Cover - anchors soil and slows water
Mechanical - reduce slope length and steepness
Tillage - cover to reduce runoff, grass waterways, strip cropping, conservation tillage
Problems with weed, disease, insect control
Planting into residues
Universal Wind Erosion Equation
E - potential average annual quantity of erosion
I - soil erodibility (particle size dependent)
C - local climate factor
K - soil roughness
L - width of field (unprotected by wind barriers)
V - quantity of vegetative cover
Qualities of good windbreak
NOT SOLID WALL (wind turbulence of downwind side)
Trees and shrubs (sheltered distance increases with horizontal length of windbreak)
Cover and cultivation effects on wind erosion
Cover - holds soil, increases roughness, preserves moisture, holds snow, keeps moist in spring
Cultivation - increases surface roughness, cultivate perpendicular to prevailing wind
Gravity erosion
Landslide - rapid
Soil creep - slow, persistent
gravity erosion factors
Assisted by water which
1) decreases friction
2) Increased weight
Favored by steep slopes and clay soils or clay layers in soils
Prevented by vegetation with deep roots which use water, increasing friction, and promote root binding
Controlling physical degradation
Reduce machinery weight, reduce number of trips, keep off wet soil
Compaction can be reduced by special deep tillage methods
Crusting can reduced by light cultivation, adding gypsum, mulches
