CFP Soil Science & Analysis 3 — Questions and Answers
Question 1: Which soil property most directly influences the seepage rate from an earthen fish pond?
- Soil color
- Soil permeability (hydraulic conductivity) (Correct answer)
- Soil pH
- Cation exchange capacity
Correct answer: Soil permeability (hydraulic conductivity)
Hydraulic conductivity determines how quickly water moves through soil, directly controlling seepage losses from pond embankments.
Question 2: The presence of hardpan or fragipan in a soil profile would most concern a fisheries manager because it:
- Increases nutrient leaching below the root zone
- Restricts drainage and may cause perched water tables affecting site selection (Correct answer)
- Raises soil pH above optimal levels for aquatic plants
- Reduces the soil's cation exchange capacity significantly
Correct answer: Restricts drainage and may cause perched water tables affecting site selection
Hardpan layers restrict vertical water movement, creating perched water tables that complicate drainage and excavation for pond construction.
Question 3: Organic soils (Histosols) are generally considered poor choices for fish pond construction primarily because:
- They have excessive phosphorus that causes toxic algae blooms
- They are highly compressible, causing embankment settling and structural instability (Correct answer)
- They lack microbial communities needed for nutrient cycling
- They have pH levels too alkaline for most sport fish
Correct answer: They are highly compressible, causing embankment settling and structural instability
Histosols are poorly suited for pond embankments because organic material compresses under load, leading to structural failure.
Question 4: Which of the following soil tests is most useful for determining lime requirement in pond soils?
- Mehlich-3 extraction for phosphorus
- Shoemaker-McLean-Pratt (SMP) buffer pH test (Correct answer)
- Hydrometer method for particle size
- Loss-on-ignition for organic matter
Correct answer: Shoemaker-McLean-Pratt (SMP) buffer pH test
The SMP buffer pH test estimates the buffering capacity of acidic soils and is used to calculate lime application rates.
Question 5: Sulfidic materials (potential acid sulfate soils) in a pond site present a major risk because upon drainage or excavation they:
- Release excess calcium, raising pH to toxic levels
- Oxidize to produce sulfuric acid, dramatically lowering pH (Correct answer)
- Increase turbidity by releasing colloidal particles
- Consume dissolved oxygen through excessive organic decomposition
Correct answer: Oxidize to produce sulfuric acid, dramatically lowering pH
When sulfidic sediments are exposed to oxygen, iron sulfides oxidize to form sulfuric acid, which can drop pH below 4 and kill fish.
Question 6: In riparian soil assessments for buffer strip design, which indicator is most useful for identifying hydric soils?
- High sand content in the A horizon
- Redoximorphic features such as mottles and depleted matrices (Correct answer)
- High bulk density throughout the profile
- Presence of calcium carbonate nodules
Correct answer: Redoximorphic features such as mottles and depleted matrices
Redoximorphic features (iron mottles, gray depleted matrices) are diagnostic indicators of hydric soils formed under periodic saturation.
Question 7: A fisheries manager finds that pond soils have very low phosphorus sorption capacity. This is most likely associated with:
- High clay content with abundant iron and aluminum oxides
- Coarse sandy soils with low surface area and organic matter (Correct answer)
- High soil pH and calcium carbonate content
- Compact subsoil layers with restricted drainage
Correct answer: Coarse sandy soils with low surface area and organic matter
Sandy soils have low surface area and limited iron/aluminum oxides, resulting in poor phosphorus retention and higher risk of leaching.
CFP Soil Science & Analysis 3
Which soil property most directly influences the seepage rate from an earthen fish pond?