ISA Soil and Water Management Questions and Answers 1 — Questions and Answers
Question 1: An arborist inspects a mature street tree in a heavily used urban plaza. The soil is hard-packed, and the tree exhibits stunted growth, sparse foliage, and some branch dieback. These symptoms are most likely the primary result of which soil condition?
- High soil salinity from de-icing salts
- A chronic nutrient deficiency
- Reduced pore space limiting oxygen and water availability (Correct answer)
- Competition from surrounding turfgrass
Correct answer: Reduced pore space limiting oxygen and water availability
Heavy foot and vehicle traffic in urban areas leads to soil compaction. Compaction reduces total pore space, especially the large macropores responsible for air exchange and water movement. This deprives roots of the oxygen necessary for respiration and water absorption, leading to stress symptoms like stunted growth and dieback.
Question 2: Which of the following statements best distinguishes between soil texture and soil structure?
- Texture is the percentage of organic matter, while structure is the soil's pH level.
- Texture refers to the proportion of sand, silt, and clay, while structure describes how these particles are arranged into aggregates. (Correct answer)
- Texture can be easily modified with amendments, whereas structure is a permanent, unchangeable property.
- Texture governs nutrient availability, while structure primarily affects soil temperature.
Correct answer: Texture refers to the proportion of sand, silt, and clay, while structure describes how these particles are arranged into aggregates.
Soil texture is an inherent property determined by the relative percentages of sand, silt, and clay particles. Soil structure refers to the arrangement and binding of these particles into clumps or aggregates. While texture is largely permanent, good soil structure can be developed or destroyed through management practices.
Question 3: A homeowner wants to ensure the survival of a newly planted tree during its first dry summer. What is the most effective irrigation practice an arborist should recommend?
- Lightly sprinkle the leaves and soil surface daily to cool the tree.
- Apply water deeply and infrequently, thoroughly soaking the root ball and surrounding soil. (Correct answer)
- Water frequently with small amounts directly at the base of the trunk.
- Mix a water-soluble fertilizer with every irrigation to force rapid growth.
Correct answer: Apply water deeply and infrequently, thoroughly soaking the root ball and surrounding soil.
Deep, infrequent watering encourages the tree's roots to grow deeper into the soil profile, creating a more extensive and drought-tolerant root system. Shallow, frequent watering promotes a weak, shallow root system that is more vulnerable to drying out.
Question 4: The amount of water held in the soil after the excess has drained away due to gravity, which is considered the ideal state for plant water uptake, is known as:
- Saturation
- Permanent wilting point
- Field capacity (Correct answer)
- Hygroscopic water
Correct answer: Field capacity
Field capacity is the term used to describe the amount of soil moisture or water content held in soil after excess water has drained away and the rate of downward movement has materially decreased. At this point, the soil's micropores are filled with water and the macropores are filled with air, which is optimal for root function.
Question 5: A client's property has a low-lying area with heavy clay soil where a maple tree is failing to thrive, showing yellowed leaves and poor growth. The ground remains saturated for several days after rainfall. Which action would provide the most effective long-term solution?
- Prune the tree's crown to reduce its water needs.
- Apply a thick layer of sand over the soil surface.
- Install a French drain or grade the area to redirect surface water away from the tree. (Correct answer)
- Fertilize heavily to compensate for poor nutrient uptake.
Correct answer: Install a French drain or grade the area to redirect surface water away from the tree.
The core problem is poor drainage causing waterlogged soil, which deprives roots of oxygen. The most effective long-term solution is to physically alter the site to remove excess water, such as by installing a French drain or regrading the surface to create a swale. Fertilizing, pruning, or adding sand will not resolve the underlying issue of soil saturation.
Question 6: An arborist is preparing a tree care plan for a municipal park. To improve water retention in the soil and reduce temperature fluctuations in the root zone, which of the following practices is most recommended?
- Installing a perimeter of landscape fabric around the trees.
- Regularly aerating the soil with a deep-tine aerator.
- Applying a pre-emergent herbicide to control all weeds.
- Applying a 2- to 4-inch layer of organic mulch over the root zone. (Correct answer)
Correct answer: Applying a 2- to 4-inch layer of organic mulch over the root zone.
Applying a layer of organic mulch is a key practice in soil and water management. Mulch helps to conserve soil moisture by reducing evaporation, moderates soil temperatures to protect roots from extreme heat and cold, and can improve soil structure as it decomposes.
ISA Soil and Water Management Questions and Answers 1
An arborist inspects a mature street tree in a heavily used urban plaza.
The soil is hard-packed, and the tree exhibits stunted growth, sparse foliage, and some branch dieback.
These symptoms are most likely the primary result of which soil condition?