ISA Soil Management 2 — Questions and Answers
Question 1: Which soil texture has the highest water-holding capacity?
- Sandy loam
- Clay (Correct answer)
- Silt loam
- Sand
Correct answer: Clay
Clay soils have the highest water-holding capacity due to their large surface area and small pore spaces.
Question 2: What is the primary function of soil organic matter for tree health?
- Increases soil compaction
- Improves nutrient retention and soil structure (Correct answer)
- Raises soil pH
- Reduces microbial activity
Correct answer: Improves nutrient retention and soil structure
Soil organic matter improves cation exchange capacity, water retention, and aggregation, all benefiting tree growth.
Question 3: Soil compaction most directly damages tree roots by:
- Increasing nitrogen availability
- Reducing macropore space and oxygen diffusion (Correct answer)
- Raising soil temperature
- Decreasing water infiltration rate only
Correct answer: Reducing macropore space and oxygen diffusion
Compaction destroys macropores, limiting the oxygen supply roots need for aerobic respiration.
Question 4: Vertical mulching is used primarily to:
- Increase surface drainage
- Introduce air and organic matter into compacted soil (Correct answer)
- Raise the soil pH around tree roots
- Prevent surface erosion
Correct answer: Introduce air and organic matter into compacted soil
Vertical mulching involves drilling holes in compacted soil and filling them with compost or gravel to restore aeration.
Question 5: Which nutrient is most commonly deficient in high-pH (alkaline) soils?
- Nitrogen
- Phosphorus
- Iron (Correct answer)
- Potassium
Correct answer: Iron
Iron becomes insoluble at high pH, causing iron chlorosis characterized by interveinal yellowing on new leaves.
Question 6: What does a cation exchange capacity (CEC) value primarily indicate?
- The soil's ability to hold water
- The soil's ability to retain positively charged nutrients (Correct answer)
- The rate of organic matter decomposition
- The soil's buffering capacity against compaction
Correct answer: The soil's ability to retain positively charged nutrients
CEC measures the number of negatively charged sites in soil that hold cations like calcium, magnesium, and potassium.
Question 7: Air spading around tree roots is most commonly performed to:
- Apply herbicides without root damage
- Diagnose root problems and remediate compacted soil without harming roots (Correct answer)
- Install deep root fertilization tubes
- Grade soil slope away from the trunk
Correct answer: Diagnose root problems and remediate compacted soil without harming roots
Air spading uses compressed air to excavate soil without cutting roots, allowing root inspection and soil decompaction.
ISA Soil Management 2
Which soil texture has the highest water-holding capacity?