CATS Tree Nutrition and Fertilization 1 — Questions and Answers
Question 1: Which macronutrient is most commonly deficient in urban trees and is primarily responsible for chlorophyll production?
- Phosphorus
- Nitrogen (Correct answer)
- Potassium
- Calcium
Correct answer: Nitrogen
Nitrogen is the most commonly deficient macronutrient in urban trees and is essential for chlorophyll synthesis, making leaves green and supporting overall growth.
Question 2: What is the recommended soil pH range for optimal nutrient availability in most landscape trees in the Southwest?
- 4.5–5.5
- 5.5–6.5
- 6.0–7.0 (Correct answer)
- 7.5–8.5
Correct answer: 6.0–7.0
A soil pH of 6.0–7.0 is optimal for most landscape trees because it maximizes the availability of major and minor nutrients.
Question 3: An arborist observes interveinal chlorosis on young leaves of a tree in an Albuquerque landscape. This symptom most likely indicates a deficiency of which nutrient?
- Nitrogen
- Iron (Correct answer)
- Potassium
- Phosphorus
Correct answer: Iron
Interveinal chlorosis on young leaves is a classic symptom of iron deficiency, which is common in Albuquerque's alkaline soils where iron becomes unavailable.
Question 4: Which fertilizer application method places nutrients directly into the root zone and is most effective for trees in compacted urban soils?
- Surface broadcasting
- Foliar spray
- Deep root liquid injection (Correct answer)
- Trunk implant
Correct answer: Deep root liquid injection
Deep root liquid injection delivers nutrients directly into the active root zone, bypassing compacted surface soils and ensuring efficient uptake.
Question 5: What is the primary purpose of a slow-release fertilizer formulation compared to a soluble fertilizer?
- Lower cost per application
- Reduced risk of fertilizer burn and extended nutrient availability (Correct answer)
- Faster uptake by tree roots
- Better performance on sandy soils
Correct answer: Reduced risk of fertilizer burn and extended nutrient availability
Slow-release fertilizers reduce the risk of fertilizer burn by releasing nutrients gradually, providing extended availability over the growing season.
Question 6: According to ISA best practices, the recommended nitrogen application rate for established shade trees per year is generally:
- 0.5–1.0 lb N per 1,000 sq ft of root zone (Correct answer)
- 2–4 lb N per 1,000 sq ft of root zone
- 6–8 lb N per 1,000 sq ft of root zone
- 10+ lb N per 1,000 sq ft of root zone
Correct answer: 0.5–1.0 lb N per 1,000 sq ft of root zone
ISA guidelines recommend 0.5–1.0 lb of actual nitrogen per 1,000 sq ft of root zone area annually for established shade trees to avoid over-fertilization.
Question 7: Which of the following symptoms is most associated with potassium deficiency in trees?
- Purple coloration of young leaves
- Marginal leaf scorch and tip dieback (Correct answer)
- Pale green color throughout the canopy
- Distorted or stunted new growth
Correct answer: Marginal leaf scorch and tip dieback
Potassium deficiency typically causes marginal leaf scorch and tip dieback because potassium regulates water balance and stomatal function.
CATS Tree Nutrition and Fertilization 1
Which macronutrient is most commonly deficient in urban trees and is primarily responsible for chlorophyll production?