CATS Soil and Water 2 — Questions and Answers
Question 1: Which soil horizon is most important for tree root development and nutrient uptake?
- O horizon (organic layer)
- A horizon (topsoil) (Correct answer)
- B horizon (subsoil)
- C horizon (parent material)
Correct answer: A horizon (topsoil)
The A horizon contains the highest concentration of organic matter and microbial activity, making it critical for root growth and nutrient absorption.
Question 2: What does the term 'field capacity' refer to in soil science?
- The maximum amount of water soil can hold before flooding
- The amount of water remaining in soil after excess has drained by gravity (Correct answer)
- The minimum water content at which plants can survive
- The total pore space available in a soil sample
Correct answer: The amount of water remaining in soil after excess has drained by gravity
Field capacity is the water content remaining in soil after gravitational drainage has ceased, typically measured 24–48 hours after saturation.
Question 3: In Albuquerque's arid climate, which irrigation strategy best promotes deep root development in trees?
- Frequent shallow watering daily
- Infrequent deep watering less often (Correct answer)
- Overhead sprinkler irrigation on a timer
- Surface drip irrigation at the trunk base
Correct answer: Infrequent deep watering less often
Infrequent deep watering encourages roots to grow deeper in search of moisture, improving drought tolerance and structural stability.
Question 4: What is the primary cause of soil compaction around urban trees?
- Excessive irrigation
- Foot and vehicle traffic (Correct answer)
- High clay content alone
- Organic mulch decomposition
Correct answer: Foot and vehicle traffic
Foot and vehicle traffic are the leading causes of urban soil compaction, reducing pore space and limiting water infiltration and root growth.
Question 5: Which nutrient deficiency in alkaline Albuquerque soils most commonly causes interveinal chlorosis in trees?
- Nitrogen
- Phosphorus
- Iron (Correct answer)
- Calcium
Correct answer: Iron
Iron chlorosis is common in Albuquerque's alkaline soils because high pH locks up iron in insoluble forms, causing yellowing between leaf veins.
Question 6: What soil amendment is most commonly used to lower pH in alkaline desert soils?
- Lime
- Elemental sulfur (Correct answer)
- Perlite
- Peat moss alone
Correct answer: Elemental sulfur
Elemental sulfur is oxidized by soil bacteria to form sulfuric acid, which effectively lowers soil pH in alkaline conditions over time.
Question 7: Which of the following best describes 'wilting point' in relation to soil water?
- The water content at which soil becomes waterlogged
- The soil moisture level below which plants cannot extract water (Correct answer)
- The point at which irrigation should begin regardless of plant stress
- The maximum water-holding capacity of a given soil
Correct answer: The soil moisture level below which plants cannot extract water
The permanent wilting point is the soil moisture level at which the remaining water is held too tightly by soil particles for plant roots to extract it.
CATS Soil and Water 2
Which soil horizon is most important for tree root development and nutrient uptake?