AGEN 2363, Chpt. 5 notes. Wind erosion and deposition.
I. Three things that can lead to wind erosion (know these):
1. loose soil
2. smooth and bare surface
3. strong, sustained winds (simple)
II. Three basic ways to prevent wind erosion (opposite of above!)
1. crop management to encourage soil aggregation
2. keep soil surface rough and vegetated or mulched
3. utilize wind breaks (small and large) to reduce wind velocity
A. Two primary means of wind transport:
1. suspension (primarily silt and clay)
2. saltation (primarily fine sand to sand size particles or aggregates)
TRIVIA note: saltated sand grains ‘jump up’ about ¼ of the distance traveled.
B. Wind erosion damage:
- loss of soil productivity, - abrasion, - covering of fences, roads, structures,
- air pollution, - stream sedimentation, - desert pavements – define
C. friction velocity = relation of wind velocity to erosive energy at the soil surface.
D. avalanching = increased rate of wind erosion as the wind blows farther across a field.
1. Three main factors related to soil avalanching:
1) accumulation of eroded material at end of field from previous events.
These particles are more susceptible to wind erosion.
2) increase in the number of saltated particles.
3) smoother surfaces
E. transportation capacity of wind is a function of the friction velocity and increases by a
proportion factor of 5, or:
X = function of (u’*)5, X = transport capacity (g/cm2), u’* = friction velocity
F. sand blows have greater amounts of soil transported but usually less fertile soil,
dust storms usually have lesser amounts of soil, but it is more fertile and may contain
absorbed pesticides such as pre-emergence herbicides!
G. The most effective way to control wind erosion is to maintain a thick vegetative cover!
ridge till - define
II. Summary: factors affecting wind erosion.
- wind velocity, friction velocity - soil texture, aggregation
- topography - soil moisture
- soil surface roughness - time of year, prevailing winds
- length of field across the wind direction - soil particle roughness (esp. sand)