CATS Soil and Water 3 — Questions and Answers
Question 1: What is the typical ideal soil pH range for most landscape trees?
- 4.0–5.0
- 5.5–7.0 (Correct answer)
- 7.5–8.5
- 8.5–9.5
Correct answer: 5.5–7.0
Most landscape trees thrive in a slightly acidic to neutral pH range of 5.5–7.0, where the majority of nutrients are soluble and available.
Question 2: Which soil texture class has the highest water-holding capacity?
- Sandy soil
- Loamy sand
- Clay soil (Correct answer)
- Gravelly soil
Correct answer: Clay soil
Clay soils have the highest water-holding capacity due to their very small particle size and large surface area, though drainage can be poor.
Question 3: What is the function of mycorrhizal fungi in relation to tree water uptake?
- They decompose organic matter to release water
- They extend the effective root surface area, improving water and nutrient absorption (Correct answer)
- They fix atmospheric nitrogen into the soil for roots
- They prevent excessive water loss from roots
Correct answer: They extend the effective root surface area, improving water and nutrient absorption
Mycorrhizal fungi form symbiotic associations with tree roots, dramatically increasing the absorptive surface area for water and nutrients.
Question 4: How does soil organic matter primarily improve water relations in sandy soils?
- It increases soil pH, allowing better water flow
- It increases the soil's water-holding capacity and reduces drainage losses (Correct answer)
- It compacts the sandy particles to trap water
- It reduces evaporation by forming a surface crust
Correct answer: It increases the soil's water-holding capacity and reduces drainage losses
Organic matter holds many times its weight in water through hydrogen bonding, significantly improving the water retention of coarse sandy soils.
Question 5: In New Mexico, which soil condition is most likely to cause waterlogged conditions injurious to tree roots?
- A caliche layer impeding deep drainage (Correct answer)
- Overly sandy texture promoting rapid percolation
- Excessively high organic matter content
- Low calcium levels in the B horizon
Correct answer: A caliche layer impeding deep drainage
Caliche (calcium carbonate hardpan) creates an impermeable layer that prevents downward drainage, causing water to pool above it and drown roots.
Question 6: Which irrigation method is generally most water-efficient for established trees in arid climates?
- High-volume overhead sprinklers
- Surface flooding around the trunk
- Deep root watering with low-volume drip emitters (Correct answer)
- Spray heads at the canopy drip line
Correct answer: Deep root watering with low-volume drip emitters
Deep root drip irrigation delivers water directly to the root zone with minimal evaporation loss, making it the most efficient method in arid conditions.
Question 7: What does high electrical conductivity (EC) in irrigation water indicate for tree health?
- The water has ideal mineral content for tree growth
- The water has high dissolved salt levels that may cause root stress (Correct answer)
- The water is highly oxygenated and beneficial to roots
- The water pH is optimal for nutrient uptake
Correct answer: The water has high dissolved salt levels that may cause root stress
High EC indicates elevated dissolved salts, which can cause osmotic stress that prevents roots from absorbing water, leading to drought-like symptoms.
CATS Soil and Water 3
What is the typical ideal soil pH range for most landscape trees?