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Botany and Soils > Lecture 10: All About Soil > Flashcards

Lecture 10: All About Soil Flashcards

1
Q

What is soil?

A

Unconsolidated cover of the earth, made up of mineral and organic components, water and air, and capable of supporting plant growth

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2
Q

What is dirt?

A

Displaced soil

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3
Q

Is soil a renewable resource?

A

No

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4
Q

What are the different profiles of soil?

A

O Horizon/Layer
A Horizon/Layer
B Horizon/Layer
C Horizon/Layer
R Horizon/Layer

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5
Q

What is the O Horizon?

A

Soil profile that is found in undisturbed fields of forests made of organic matter consisting of plant matter in varying degrees of decomposition

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6
Q

What is A horizon?

A

Topsoil with mineral soil mixed with organic matter.

There are fewer organisms towards the base of the layer

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7
Q

What is B Horizon profile?

A

Subsoil that is usually nutrient rich. It may contain some organic matter.

It has lower concentrations of oxygen and is less penetrable by roots

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8
Q

What is C Horizon soil?

A

Lower subsoil made mostly of mineral rock being broken down.

You will see particles of different sizes

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9
Q

What is R Horizon

A

It is the parent bedrock

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10
Q

How are soil horizons developed?

A

Develop from parent materials

There are variations of parent materials all around the world so soils are not the same everywhere

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11
Q

What is weathering?

A

The break down of rocks into soil

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12
Q

What are the different types of physical weathering?

A

Freezing and thawing
Heating and cooling
Unloading (exfoliation)
Wetting and drying
Grinding or rubbing (Abrasion)
Organism activity

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13
Q

What is freezing and thawing weathering?

A

Water accumulates in an opening of a rock, the water freezes and expands.

Expansive may be big enough to break the rock

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14
Q

What is heating and cooling weathering?

A

Alternating cycles of heating and cooling can cause different minerals in the rock to expand and contract to varying degrees

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15
Q

What is unloading weathering?

A

Release of pressure (erosion) on top of a rock allows the rock to expand and break in sheets along the joints

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16
Q

What is wetting and drying weathering?

A

Different rocks absorb varying amounts of water and the water absorption causes swelling in the rock. Drying in the rock causes contractions.

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17
Q

What is the grinding or rubbing weathering?

A

Movement of rocks between each other, or movement between rocks.

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18
Q

What is organism activity weathering?

A

Caused by living organisms including humans.

Tree roots can grow in and widen cracks in rocks. Animals that tunnel or dig or move on soil can gradually break down rock

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19
Q

What does soil consist of? What are the components of soil?

A

Mineral particles
Organic materials
Living organisms
Air
Water

20
Q

What are the three categories of mineral particles in soil?

A

Sand, silt, clay

Sand is like a basket ball, silt is like a baseball, clay is like a golf ball

21
Q

What are the characteristics of sandy soils?

A

Large spaces between particles
Little water holding capacity
Low cohesiveness between particles
Holds fewer plant nutrients
Large capacity for aeration
Warms up and cools down faster than other soils

22
Q

What are the characteristics of silty soil?

A

Better water holding capacity than sandy soils
Moderate to high nutrient levels, high fertility rating
Low to moderate cohesiveness
Can be easily washed away by rain
Overtilling can cause compaction
Can harden in dry conditions

23
Q

What are the characteristics of clay soils?

A

High capacity to hold water
High cohesiveness between particles
May be in nutrients, but tight binding to particles may make them unavailable to plants
Take longer to drain and warm up
Become hard when dry

24
Q

What are the characteristics of loam?

A

Equal proportions of sand and silt, and less of clay
Good drainage, fertility, aeration, water retention
Easy to work with, loose and crumbly texture
Easy for roots to grow in

25
Q

What is soil structure?

A

Arrangement of sand, silt, and clay particles into clumps, known as aggregates.

26
Q

Why is it important to have good soil structure?

A

Important for plant growth as it allows water and air to enter the soil and nutrients to be available

27
Q

What are the 7 different categories of soil structure?

A

Granular
Platy
Blocky
Prismatic
Columnar
Massive
Single grain

28
Q

What is granular soil structure?

A

Most ideal soil structure
It has a good amount of drainage, aeration and biological activity.
It’s easy to work with and allows for the good development of plant roots.
Aggregates are 2 to 5 mm in diameter

29
Q

What is platy soil structure?

A

Thin horizontal layers of soil often seen in compacted soils. May prevent root growth through the layer

30
Q

What is a blocky soil structure?

A

Aggregates are irregularly shaped, or cube like. Usually 5 to 50 mm in diameter with sharp or dull edges

31
Q

What is prismatic soil structure?

A

Aggregates are taller than they are wide with flat tops.

32
Q

What is a columnar soil structure?

A

Similar to prismatic soil structures but with rounded tops. Often found in salt affected soils

33
Q

What are massive soil structures?

A

Soil does not have any large pores. It’s effectively a massive block.

34
Q

What is single grain soil structure?

A

No aggregation or definite arrangement of soil particles. Usually found in coarse grained soils like beach sand.

35
Q

What are micropores?

A

Usually less than 0.08 mm and are usually located within aggregates (inside the aggregate)

36
Q

What is a macropore?

A

Usually has diameters greater than 0.08 mm and are located inbetween aggregate particles.

37
Q

Sketch a typical soil profile and label the layers.

A

Draw on paper

38
Q

What is the process of breaking down rocks into soil called?

A

Weathering

39
Q

What is the proportion of sand, silt, and clay particles in soil called?

A

Soil texture (not how the soil feels) aka percentage of sand, silt and clay particles

40
Q

What type of soil structure is ideal for plant growth?

A

Granular soil structure

41
Q

What is a ped?

A

Groups of aggregates may stick together to form large clumps

42
Q

What is the particle size of sand?

A

0.05mm to 2mm

43
Q

What is the particle size of silt?

A

0.002mm to 0.05mm

44
Q

What is the particle size of clay?

A

Less than 0.002mm

45
Q

What is the ideal soil texture for plants to grow in?

A

Loamy soil

46
Q

What do soil horizons develop from?

A

Parent materials

Botany and Soils (16 decks)

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