NYC Horticulturist Exam 2026 LATEST: 200
Questions & Answers with Rationales – Complete
DCAS Study Guide
Section 1: Soil Science & Plant Nutrition (Questions 1–40)
1. What does pH stand for?
A. Plant hormones
B. Potential hydrogen
C. Phosphorus hydrogen
D. Percent humus
Correct Answer: B. Potential hydrogen
pH stands for 'potential hydrogen' — it measures the concentration of hydrogen ions in a
solution, indicating acidity or alkalinity on a scale of 0–14. Low pH = high hydrogen ion
concentration = acidic; high pH = low hydrogen ion concentration = alkaline.
2. What pH value is considered neutral?
A. 5.0
B. 6.0
,C. 7.0
D. 8.0
Correct Answer: C. 7.0
A pH of 7.0 is considered perfectly neutral — neither acidic nor alkaline. Values below 7.0
are acidic; values above 7.0 are alkaline (basic). Pure water has a pH of 7.0.
3. What pH range do most ornamental plants prefer?
A. 4.0–5.5
B. 5.5–6.5
C. 6.0–7.0
D. 7.5–8.5
Correct Answer: C. 6.0–7.0
Most ornamental landscape plants prefer a slightly acidic to neutral soil pH in the range of
6.0–7.0. Within this range, most essential nutrients are readily available for plant uptake.
Outside this range, nutrients may become 'locked up' even if present in the soil.
4. A soil with a pH of 5.0 is how many times more acidic than a soil with a pH of 7.0?
A. 10 times
B. 50 times
C. 100 times
D. 1,000 times
Correct Answer: C. 100 times
The pH scale is logarithmic — each unit represents a 10-fold change in acidity. A pH of 5.0
vs 7.0 is a difference of 2 units, so it is 10 × 10 = 100 times more acidic. This logarithmic
relationship is why small pH changes require significant soil amendments.
,5. A soil with a pH of 5.0 is how many times more acidic than a soil with a pH of 6.0?
A. 2 times
B. 5 times
C. 10 times
D. 100 times
Correct Answer: C. 10 times
One unit on the pH scale represents a 10-fold change. A pH of 5.0 is exactly 1 unit lower
than 6.0 — therefore it is 10 times more acidic. This is why precise soil pH management
matters: going from 6.0 to 5.0 dramatically changes nutrient availability.
6. Which amendment is applied to LOWER soil pH (make it more acidic)?
A. Agricultural (Ag) limestone
B. Wood ash
C. Sulfur
D. Bone meal
Correct Answer: C. Sulfur
Elemental sulfur is applied to soil to LOWER pH (increase acidity). Soil bacteria convert
sulfur to sulfuric acid over time, lowering the pH. It is commonly used for acid-loving plants
like blueberries, azaleas, and rhododendrons where soil pH needs to be reduced.
7. Which amendment is applied to RAISE soil pH (make it less acidic)?
A. Sulfur
B. Agricultural (Ag) limestone
C. Ammonium sulfate fertilizer
D. Peat moss
, Correct Answer: B. Agricultural (Ag) limestone
Agricultural (Ag) limestone (calcium carbonate) is applied to RAISE soil pH — to make
acidic soil less acidic (more alkaline). The calcium carbonate neutralizes soil acidity. Ground
limestone is slower acting but longer lasting than other liming materials.
8. Which two factors change soil pH most rapidly?
A. Sun exposure and wind
B. Organic matter and rainfall
C. Fertilizer and temperature
D. Soil texture and slope
Correct Answer: B. Organic matter and rainfall
Organic matter decomposition releases organic acids that lower pH, while rainfall leaches
basic cations from the soil, also lowering pH. These two factors have the most rapid and
significant impact on soil pH in NYC's climate.
9. Which soil texture generally provides the best balance of drainage and water
retention for most landscape plants?
A. Sand
B. Clay
C. Loam
D. Silt
Correct Answer: C. Loam
Loam contains a balanced mix of sand, silt, and clay, offering good drainage while retaining
adequate moisture and nutrients. This makes it the ideal soil texture for most landscape
plants.
Questions & Answers with Rationales – Complete
DCAS Study Guide
Section 1: Soil Science & Plant Nutrition (Questions 1–40)
1. What does pH stand for?
A. Plant hormones
B. Potential hydrogen
C. Phosphorus hydrogen
D. Percent humus
Correct Answer: B. Potential hydrogen
pH stands for 'potential hydrogen' — it measures the concentration of hydrogen ions in a
solution, indicating acidity or alkalinity on a scale of 0–14. Low pH = high hydrogen ion
concentration = acidic; high pH = low hydrogen ion concentration = alkaline.
2. What pH value is considered neutral?
A. 5.0
B. 6.0
,C. 7.0
D. 8.0
Correct Answer: C. 7.0
A pH of 7.0 is considered perfectly neutral — neither acidic nor alkaline. Values below 7.0
are acidic; values above 7.0 are alkaline (basic). Pure water has a pH of 7.0.
3. What pH range do most ornamental plants prefer?
A. 4.0–5.5
B. 5.5–6.5
C. 6.0–7.0
D. 7.5–8.5
Correct Answer: C. 6.0–7.0
Most ornamental landscape plants prefer a slightly acidic to neutral soil pH in the range of
6.0–7.0. Within this range, most essential nutrients are readily available for plant uptake.
Outside this range, nutrients may become 'locked up' even if present in the soil.
4. A soil with a pH of 5.0 is how many times more acidic than a soil with a pH of 7.0?
A. 10 times
B. 50 times
C. 100 times
D. 1,000 times
Correct Answer: C. 100 times
The pH scale is logarithmic — each unit represents a 10-fold change in acidity. A pH of 5.0
vs 7.0 is a difference of 2 units, so it is 10 × 10 = 100 times more acidic. This logarithmic
relationship is why small pH changes require significant soil amendments.
,5. A soil with a pH of 5.0 is how many times more acidic than a soil with a pH of 6.0?
A. 2 times
B. 5 times
C. 10 times
D. 100 times
Correct Answer: C. 10 times
One unit on the pH scale represents a 10-fold change. A pH of 5.0 is exactly 1 unit lower
than 6.0 — therefore it is 10 times more acidic. This is why precise soil pH management
matters: going from 6.0 to 5.0 dramatically changes nutrient availability.
6. Which amendment is applied to LOWER soil pH (make it more acidic)?
A. Agricultural (Ag) limestone
B. Wood ash
C. Sulfur
D. Bone meal
Correct Answer: C. Sulfur
Elemental sulfur is applied to soil to LOWER pH (increase acidity). Soil bacteria convert
sulfur to sulfuric acid over time, lowering the pH. It is commonly used for acid-loving plants
like blueberries, azaleas, and rhododendrons where soil pH needs to be reduced.
7. Which amendment is applied to RAISE soil pH (make it less acidic)?
A. Sulfur
B. Agricultural (Ag) limestone
C. Ammonium sulfate fertilizer
D. Peat moss
, Correct Answer: B. Agricultural (Ag) limestone
Agricultural (Ag) limestone (calcium carbonate) is applied to RAISE soil pH — to make
acidic soil less acidic (more alkaline). The calcium carbonate neutralizes soil acidity. Ground
limestone is slower acting but longer lasting than other liming materials.
8. Which two factors change soil pH most rapidly?
A. Sun exposure and wind
B. Organic matter and rainfall
C. Fertilizer and temperature
D. Soil texture and slope
Correct Answer: B. Organic matter and rainfall
Organic matter decomposition releases organic acids that lower pH, while rainfall leaches
basic cations from the soil, also lowering pH. These two factors have the most rapid and
significant impact on soil pH in NYC's climate.
9. Which soil texture generally provides the best balance of drainage and water
retention for most landscape plants?
A. Sand
B. Clay
C. Loam
D. Silt
Correct Answer: C. Loam
Loam contains a balanced mix of sand, silt, and clay, offering good drainage while retaining
adequate moisture and nutrients. This makes it the ideal soil texture for most landscape
plants.
