ISA Certified Arborist — Practice Exam
Soil management: practice questions
Our ISA Certified Arborist bank has 21 questions on this topic. Here are 5 of them with answers; the full mock exam draws from every topic, like the real one.
Question 1
What is a 'mulch volcano'?
- Mulch that has caught fire in summer
- A ring of stones around a tree
- Excessive mulch piled around the base of a tree
- Mulch spread out to the drip line
Show the answer
C. Excessive mulch piled around the base of a tree — Build-up happens when reapplication outpaces decomposition.
Question 2
Which lawn product can injure or kill nearby trees?
- Preemergent herbicides
- 'Weed and feed' that kills broadleaf weeds
- Plain water
- Wood chip mulch
Show the answer
B. 'Weed and feed' that kills broadleaf weeds — Most deciduous trees are broadleaved; preemergent herbicides are safe near trees.
Question 3
Which instrument measures soil compaction by the pressure needed to push a probe into the soil?
- A clinometer
- A pH meter
- A penetrometer
- A tensiometer
Show the answer
C. A penetrometer — A spade test can approximate it: needing a pick-axe means severe compaction.
Question 4
Which mulch is described by ISA as an excellent material around trees?
- Shredded rubber
- Plastic sheeting covered with gravel
- Fresh grass clippings
- Fresh arborist wood chips, especially with bark and leaves
Show the answer
D. Fresh arborist wood chips, especially with bark and leaves — Organic mulches improve soil biology and fertility as they decompose.
Question 5
Why should no more than 2 inches of organic mulch be used on wet, poorly drained soils?
- Deeper mulch makes the soil dry out too quickly and raises the soil pH sharply
- Deeper mulch blows away in the wind
- Deeper mulch slows drying and can cause excess root-zone moisture and root rot
- Deeper mulch raises the soil temperature too much for roots
Show the answer
C. Deeper mulch slows drying and can cause excess root-zone moisture and root rot — On wet sites, bare ground or thin inorganic mulch may be better.