Free Certified Arborist Soil Management Questions and Answers — Questions and Answers

Question 1: Which of the following soil pH levels would give plants the greatest availability of iron?

4
5 (Correct answer)
9
7

Correct answer: 5

Iron availability to plants is highly dependent on soil pH. Iron becomes less soluble and thus less available as the pH increases (becomes more alkaline). Therefore, a slightly acidic pH, such as 5, provides the greatest availability of iron for plant uptake, preventing iron chlorosis and ensuring proper plant nutrition.

Question 2: Which kind of bacteria are essential for the humus to be produced?

Actinomycetes (Correct answer)
Nitrospirae
Aquificae
Proteobacteria

Correct answer: Actinomycetes

Actinomycetes are a group of bacteria that play a crucial role in the decomposition of complex organic matter in soil, such as cellulose and lignin. Their activity is essential for the formation of stable humus, which improves soil structure, water retention, and nutrient availability. They are often responsible for the characteristic earthy smell of healthy soil.

Question 3: After all gravitational water has drained and the soil has both accessible and unavailable water, what condition is it in?

Saturation
Permanent wilting point
Field capacity (Correct answer)
Irrigation

Correct answer: Field capacity

Field capacity is the amount of water remaining in the soil after all gravitational water has drained away, typically 2-3 days after a thorough wetting. At this point, the soil holds the maximum amount of water available for plant uptake against the force of gravity, while some water is held too tightly for plants to access. It represents an optimal moisture level for plant growth.

Question 4: Leaching is known as:

A tree's gradual decline due to inadequate sunlight.
The method by which water removes chemicals from soil. (Correct answer)
The act of insects removing nutrients from a tree.
The improvement in root health following soil aeration.

Correct answer: The method by which water removes chemicals from soil.

Leaching is the process by which water percolates through the soil profile, dissolving and carrying away soluble nutrients, minerals, and other chemicals. This can be beneficial by removing excess salts, but it can also lead to the loss of essential plant nutrients from the root zone, especially in sandy soils or with excessive irrigation. It's a key process in nutrient cycling.

Question 5: What is resistance to changes in pH?

Buffering capacity (Correct answer)
Volatilization
Infiltration rate
Cation exchange capacity

Correct answer: Buffering capacity

Buffering capacity refers to the ability of a soil to resist changes in its pH when acids or bases are added. Soils with high buffering capacity, often those rich in organic matter or clay, can neutralize these additions, maintaining a relatively stable pH. This stability is crucial for nutrient availability and microbial activity, which are sensitive to pH fluctuations.

Question 6: Which metric provides the best indication of soil fertility?

Water-holding capacity
Soil pH
Cation exchange capacity (Correct answer)
Buffering capacity

Correct answer: Cation exchange capacity

Cation exchange capacity (CEC) is a measure of the soil's ability to hold and exchange positively charged nutrient ions (cations) like calcium, magnesium, and potassium. A higher CEC indicates that the soil can retain more essential nutrients, making them available to plants, and thus is a strong indicator of soil fertility. It directly reflects the soil's nutrient-holding capacity.

Question 7: What is meant by the term "reference evapotranspiration measure"?

The expected quantity of plant and soil water loss considering the location and the current vegetation. (Correct answer)
The typical rainfall in a certain location.
The average amount of water in a species' foliage.
The water source in a certain location.

Correct answer: The expected quantity of plant and soil water loss considering the location and the current vegetation.

Reference evapotranspiration (ETo) is a measure of the rate at which water would evaporate from a standardized reference crop (like grass) under specific climatic conditions, assuming no water limitations. It provides a baseline for estimating the water requirements of other crops and landscapes. This measure accounts for both evaporation from the soil surface and transpiration from plants, helping manage irrigation efficiently.

Question 8: What is the primary purpose of xeriscaping in landscaping

To protect the landscape against frost.
To protect the landscape against flood.
To protect the landscape against drought. (Correct answer)
To protect the landscape against sunburn.

Correct answer: To protect the landscape against drought.

Xeriscaping is a landscaping method specifically designed to reduce or eliminate the need for irrigation. It achieves this by using drought-tolerant plants, efficient irrigation techniques, mulching, and thoughtful design principles. Its primary goal is water conservation, making landscapes resilient to drought conditions and reducing water usage.

Question 9: In the fertilizer analysis displayed on the container, which of the following is not a standard component?

Total nitrogen
Potassium phosphate (Correct answer)
Soluble potash
Phosphoric acid

Correct answer: Potassium phosphate

Fertilizer analyses are typically expressed as N-P-K ratios, representing the percentage by weight of total nitrogen (N), available phosphate (P2O5), and soluble potash (K2O). While potassium and phosphate are components, 'potassium phosphate' itself is not a standard component listed on a fertilizer label in this specific combined form. Instead, the individual forms of phosphorus (as phosphoric acid) and potassium (as soluble potash) are listed.

Question 10: Which of the following DOES NOT always belong in the complete fertilizer?

Calcium (Correct answer)
Phosphorus
Nitrogen
Potassium

Correct answer: Calcium

A 'complete fertilizer' is defined as one that contains the three primary macronutrients: nitrogen (N), phosphorus (P), and potassium (K). While calcium is an essential plant nutrient, it is considered a secondary macronutrient and is not always included in the N-P-K formulation of a complete fertilizer. Many soils naturally contain sufficient calcium, or it may be added separately.

Question 11: What is the top horizon in a soil profile?

A
B
C
0 (Correct answer)

Correct answer: 0

The O horizon is the uppermost layer of a soil profile, primarily composed of organic matter in various stages of decomposition. This layer includes leaf litter, twigs, and humus, which contribute significantly to soil fertility, water retention, and structure. It sits above the mineral soil horizons (A, B, C).

Free Certified Arborist Soil Management Questions and Answers

Which of the following soil pH levels would give plants the greatest availability of iron?