Landscape Design Soil Science and Site Analysis 1 — Questions and Answers
Question 1: What are the three primary soil texture classes in the USDA soil texture triangle?
- Clay, silt, and gravel
- Sand, silt, and clay (Correct answer)
- Topsoil, subsoil, and bedrock
- Loam, humus, and peat
Correct answer: Sand, silt, and clay
The USDA soil texture triangle categorizes soils based on proportions of sand, silt, and clay particles.
Question 2: What does a soil percolation test measure in landscape site analysis?
- Soil pH
- The rate at which water drains through the soil (Correct answer)
- Soil nutrient levels
- Compaction depth
Correct answer: The rate at which water drains through the soil
A percolation test determines drainage rate by measuring how quickly water infiltrates, guiding decisions about drainage improvements.
Question 3: Which soil amendment is commonly added to heavy clay soil to improve drainage and aeration?
- Peat moss alone
- Coarse sand or grit, along with organic matter (Correct answer)
- Lime
- Topsoil
Correct answer: Coarse sand or grit, along with organic matter
Coarse sand improves drainage by increasing pore space, while organic matter improves overall soil structure in clay.
Question 4: What is the purpose of a 'topographic survey' in landscape design site analysis?
- To identify plant species on site
- To map existing grade elevations and slopes across the site (Correct answer)
- To test soil chemistry
- To locate underground utilities
Correct answer: To map existing grade elevations and slopes across the site
A topographic survey establishes existing elevation contours that inform grading, drainage, and design decisions.
Question 5: What does a 'soil compaction test' using a penetrometer measure?
- Soil moisture content
- The resistance of soil to penetration, indicating compaction level (Correct answer)
- Soil pH
- Presence of soil pathogens
Correct answer: The resistance of soil to penetration, indicating compaction level
A penetrometer measures pounds per square inch (psi) of soil resistance, indicating how compacted a soil is.
Question 6: Which landscape condition is indicated by a high water table near the soil surface?
- Drought stress potential
- Poor drainage and risk of root suffocation for non-wetland plants (Correct answer)
- High nutrient availability
- Sandy soil texture
Correct answer: Poor drainage and risk of root suffocation for non-wetland plants
A high water table saturates the soil root zone, depriving roots of oxygen and causing root rot in non-adapted plants.
Landscape Design Soil Science and Site Analysis 1
What are the three primary soil texture classes in the USDA soil texture triangle?