CCA Soil and Water Conservation 3 — Questions and Answers
Question 1: Which of the following best describes 'rill erosion'?
- Large gully channels that cannot be crossed with equipment
- Small concentrated flow channels that can be removed by tillage (Correct answer)
- Sheet removal of soil uniformly across a slope
- Detachment of soil by raindrop impact
Correct answer: Small concentrated flow channels that can be removed by tillage
Rill erosion forms small, concentrated channels that are shallow enough to be obliterated by normal tillage operations, unlike gullies.
Question 2: A constructed pond built across a drainage way to intercept runoff and allow sediment to settle is called a:
- Retention pond
- Sediment basin (Correct answer)
- Dry dam
- Detention basin
Correct answer: Sediment basin
A sediment basin is specifically designed to trap sediment from runoff before water leaves the field or construction site.
Question 3: The Revised Universal Soil Loss Equation (RUSLE) improved upon USLE primarily by:
- Replacing the erosivity factor with a simpler index
- Accounting for temporal variability in cover and soil conditions (Correct answer)
- Eliminating the need for slope data
- Adding a wind erosion component
Correct answer: Accounting for temporal variability in cover and soil conditions
RUSLE accounts for seasonal changes in cover, soil erodibility, and other factors on a sub-annual basis, making it more accurate than USLE.
Question 4: Which cover crop would be MOST effective at reducing wind erosion over winter in the Great Plains?
- Crimson clover
- Winter rye (Correct answer)
- Sunn hemp
- Buckwheat
Correct answer: Winter rye
Winter rye is cold-hardy and establishes quickly, providing ground cover and surface roughness that significantly reduces wind erosion over winter.
Question 5: Infiltration rate in a compacted soil layer can BEST be improved by:
- Applying gypsum at the surface
- Deep tillage (subsoiling) through the compacted layer (Correct answer)
- Increasing irrigation frequency
- Adding potassium fertilizer
Correct answer: Deep tillage (subsoiling) through the compacted layer
Subsoiling fractures the compacted layer, restoring macropore channels and allowing water to infiltrate more rapidly.
Question 6: Which watershed-scale metric is used to estimate runoff volume in the NRCS curve number method?
- Potential maximum retention (S) (Correct answer)
- Hydraulic conductivity (Ksat)
- Soil texture index (STI)
- Erodibility factor (K)
Correct answer: Potential maximum retention (S)
The potential maximum retention (S) is calculated from the curve number and represents the soil's capacity to absorb rainfall before runoff begins.
Question 7: Phosphorus loss to surface water from agricultural fields is MOST commonly associated with:
- Leaching through the soil profile
- Sediment-bound phosphorus in surface runoff (Correct answer)
- Volatilization during wet conditions
- Deep percolation to groundwater
Correct answer: Sediment-bound phosphorus in surface runoff
Phosphorus binds strongly to soil particles and is primarily lost via surface runoff carrying eroded sediment.
CCA Soil and Water Conservation 3
Which of the following best describes 'rill erosion'?