ISA Arborist Certification Chapter 3 - Soil
Science questions and answers 2024\2025
A+ Grade
organic layer
- correct answer 0 Horizon, an unaltered soil, thin layer of decomposing organic matter
Loam
- correct answer A mix of three different particle sizes and is often considered an ideal soil texture
because of the favorable characteristics for plant growth.
Not made up of equal mix of sand, silt, clay. Contains less clay
Topsoil
- correct answer commonly known as the uppermost layers (O,A,E, and sometimes the upperpart of B
horizon)
C Horizon
- correct answer Deepest Soil layer composed of partially weathered parent material. Soil in this horizon
is continually forming.
A Horizon
- correct answer Contains most of the fine absorbing roots of trees and is very biologically active. Rich in
organic matter.
E Horizon
- correct answer Between the A and B Horizon, lacks the organic matter as in A, has lighter color due to
this.
, Absorbing Roots
- correct answer Roots found in the upper 6-10 inches of soil
Roots
- correct answer Few_____ grow deeper than 3 to 4 ft.
Soil Structure
- correct answer Shape, size, strength, and arrangement of soil aggregates form ____.
Micropores
- correct answer Soil pores that retain water and are the source of available water to plants between
rainfalls.
Macropores
- correct answer Soil pores too large to hold water against the force of gravity and become filled with air
as water drains from the soil.
Bulk Density
- correct answer Mass of dried soil per unit of undisturbed soil volume. Can be used to assess whether
adequate pore space exists.
Sand
- correct answer Soils with a high percentage of _________ are less prone to compaction.
Clay
- correct answer Soils with a high percentage of ______ are easily compacted.
pH
- correct answer The measure of the acidity or alkalinity of soil.
pH 7
- correct answer pH neutrality
Science questions and answers 2024\2025
A+ Grade
organic layer
- correct answer 0 Horizon, an unaltered soil, thin layer of decomposing organic matter
Loam
- correct answer A mix of three different particle sizes and is often considered an ideal soil texture
because of the favorable characteristics for plant growth.
Not made up of equal mix of sand, silt, clay. Contains less clay
Topsoil
- correct answer commonly known as the uppermost layers (O,A,E, and sometimes the upperpart of B
horizon)
C Horizon
- correct answer Deepest Soil layer composed of partially weathered parent material. Soil in this horizon
is continually forming.
A Horizon
- correct answer Contains most of the fine absorbing roots of trees and is very biologically active. Rich in
organic matter.
E Horizon
- correct answer Between the A and B Horizon, lacks the organic matter as in A, has lighter color due to
this.
, Absorbing Roots
- correct answer Roots found in the upper 6-10 inches of soil
Roots
- correct answer Few_____ grow deeper than 3 to 4 ft.
Soil Structure
- correct answer Shape, size, strength, and arrangement of soil aggregates form ____.
Micropores
- correct answer Soil pores that retain water and are the source of available water to plants between
rainfalls.
Macropores
- correct answer Soil pores too large to hold water against the force of gravity and become filled with air
as water drains from the soil.
Bulk Density
- correct answer Mass of dried soil per unit of undisturbed soil volume. Can be used to assess whether
adequate pore space exists.
Sand
- correct answer Soils with a high percentage of _________ are less prone to compaction.
Clay
- correct answer Soils with a high percentage of ______ are easily compacted.
pH
- correct answer The measure of the acidity or alkalinity of soil.
pH 7
- correct answer pH neutrality
