3. SOIL SCIENCE WORKBOOK QUESTIONS Flashcards
Where are the majority of fine, absorbing tree roots found?
The O horizon
What are the three main properties used to describe soil?
- Physical
- Chemical
- Biological
What is soil compaction?
An increase in bulk density and a decrease in total pore space
True or False: Negatively charged clay particles hold cations near their surface.
True
True or False: Soil stress, especially in urban soils, is a major cause of tree decline.
True
True or False: Soil can hold water so tightly in micropores that tree roots cannot absorb it.
True
Rank soil textures from finest to coarsest.
Clay → Silt → Sand
On the pH scale, what do the following values indicate? Less than 7, Exactly 7, More than 7.
- Less than 7: Acidic
- Exactly 7: Neutral
- More than 7: Alkaline
True or False: Mulching can improve soil structure, reduce compaction, and add organic matter.
True
How much more acidic is a pH of 5 compared to a pH of 7?
100 times more acidic
What is the process of essential elements washing away from soil called?
Leaching
What are positively charged particles dissolved in soil water called?
Cations
What are soils with excessive soluble salts called?
Saline soils
What are soils with high sodium (Na+) content called?
Sodic soils
What is soil buffering capacity?
The resistance of soil to changes in pH
Which soils have a high buffering capacity?
- Clay soils
- Soils high in organic matter
What is the rhizosphere?
The zone of intense biological activity near actively elongating roots
What is the ‘soil food web’?
The diversity of organisms living, moving, and interacting in the soil
What is water that drains from macropores called?
Gravitational water
True or False: Most soil organisms cause disease or decay in tree roots.
False
True or False: Many tree roots have a symbiotic relationship with fungi.
True
How can compaction around established trees be improved?
Air excavation devices (e.g., Air Spade)
Match the term ‘Sand’ with its definition.
Coarse-textured soil particles
Match the term ‘Buffering capacity’ with its definition.
Resistance to pH changes
Match the term ‘Field capacity’ with its definition.
Soil after gravitational water has drained
Match the term ‘Rhizosphere’ with its definition.
Soil zone surrounding roots
Match the term ‘Macropores’ with its definition.
Tend to be air-filled
Match the term ‘Mycorrhizae’ with its definition.
‘Fungus roots’
Match the term ‘CEC (Cation Exchange Capacity)’ with its definition.
Ability to attract/hold cations
Match the term ‘micropores’ with its definition.
Tend to be water-filled
Match the term ‘pH’ with its definition.
Measure of acidity/alkalinity
Match the term ‘Micropores’ with its definition.
Tend to be water-filled
Match the term ‘Gravitational water’ with its definition.
Drains from macropores
Why are fine, absorbing roots found near the soil surface?
Roots need both air and water
Why do microorganisms congregate in the rhizosphere?
Sugar exudates from root tips serve as food
What happens if a planting hole in clay soil is backfilled with sandy soil?
Water will drain very slowly out of the planting hole
What happens when soil is compacted?
Total pore space and macropores are reduced
What is a characteristic of sandy soils in arid regions?
Tend to become alkaline, and salts build up due to lack of heavy rainfall
Lower bulk density
lower weight
more pore space
Higher bulk density
higher weight
less pore space
The mass (weight) of dried soil per unit of soil volume. Can be used to assess whether adequate pore space exists.
Bulk Density
grams/cubic centimeter
What substance may be added to soil to temporarily lower the PH?
(A) Lime
(B) Ash
(C) Sulfur
(D) Calcium
(C) Sulfur
