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Soil Colloids and Their Functions

Total questions: 104

Worksheet time: 52hrs 0mins

Name
Class
Date
1.

Why do soil colloids remain suspended in water for a long time?

a)

Because of their small size and surface charge

b)

Due to their large mass

c)

Because they dissolve completely

d)

Because they are hydrophobic

2.

What is the primary function of colloids in soil fertility?

a)

Promote evaporation

b)

Convert nutrients into gas

c)

Retain water and nutrients

d)

Increase soil pH

3.

What are soil colloids primarily composed of?

a)

Sand, silt, and water

b)

Quartz and feldspar

c)

Clay minerals, metal oxides, and organic matter

d)

Calcium carbonate and sodium chloride

4.

Which type of soil colloid has the highest cation exchange capacity (CEC)?

a)

Vermiculite

b)

Iron oxides

c)

Kaolinite

d)

Humus

5.

Isomorphous substitution in clay minerals results in:

a)

A pH-dependent charge

b)

Reduction in colloid size

c)

Permanent negative charge

d)

Positive surface charge

6.

What is a key environmental function of soil colloids?

a)

Reducing organic matter

b)

Binding heavy metals and pollutants

c)

Promoting plant diseases

d)

Enhancing erosion

7.

What is the main contributor to constant negative charge in clay minerals?

a)

pH variation

b)

Surface ionization

c)

Isomorphous substitution

d)

Organic decomposition

8.

Which of the following promotes flocculation of soil colloids?

a)

Calcium ions

b)

Sodium ions

c)

Hydrogen ions

d)

Magnesium ions

9.

In acidic soils, which cations dominate the exchange sites?

a)

Iron and sulfur

b)

Calcium and magnesium

c)

Aluminum and hydrogen

d)

Sodium and potassium

10.

What happens to CEC in soils with pH-dependent charge when pH increases?

a)

It decreases

b)

It remains constant

c)

It turns into AEC

d)

It increases

11.

Micropores primarily serve what function?

a)

Drainage

b)

Root anchorage

c)

Water retention

d)

Gas exchange

12.

High clay content in soil typically results in which characteristic?

a)

Fast drainage

b)

Light color

c)

High water retention

d)

Low water holding

13.

What is a typical particle density of mineral soils?

a)

2.0 g/cm³

b)

2.65 g/cm³

c)

1.5 g/cm³

d)

1.0 g/cm³

14.

What is the effect of compaction on soil?

a)

Improved root growth

b)

Reduced bulk density

c)

Increased pore space

d)

Reduced air and water movement

15.

What does soil consist of by volume in a balanced state?

a)

80% solids, 20% air

b)

60% air, 40% water

c)

45% solids, 5% OM, 50% pores

d)

70% solids, 30% pores

16.

Which term refers to the soil's ease of tillage and seedbed preparation?

a)

Tilth

b)

Texture

c)

Porosity

d)

Structure

17.

Which soil structure type is considered most suitable for root growth?

a)

Granular

b)

Columnar

c)

Platy

d)

Massive

18.

Which soil horizon is most likely to exhibit granular structure?

a)

B horizon

b)

R horizon

c)

C horizon

d)

A horizon

19.

Capillary action in soil is driven by what forces?

a)

Gravity and suction

b)

Adhesion and cohesion

c)

Evaporation and infiltration

d)

Moisture and dryness

20.

What soil condition often results from high water saturation?

a)

Soil cracking

b)

Good aeration

c)

Fast drying

d)

Anaerobic environment

21.

Which method is commonly used in the field to estimate soil texture?

a)

Munsell test

b)

Water test

c)

pH test

d)

Ribbon test

22.

The Munsell color system includes which three elements?

a)

Warmth, depth, hue

b)

Hue, value, chroma

c)

Light, shade, tone

d)

Texture, moisture, color

23.

Which structure restricts root growth due to horizontal layering?

a)

Massive

b)

Blocky

c)

Platy

d)

Granular

24.

Which is an example of soil degradation?

a)

Erosion

b)

Nutrient cycling

c)

Composting

d)

Crop rotation

25.

Which soil contains high organic matter?

a)

Vertisol

b)

Spodosol

c)

Aridisol

d)

Histosol

26.

A primary threat to soil in urban areas is:

a)

Compaction

b)

Photosynthesis

c)

Nutrient cycling

d)

Infiltration

27.

Which soil order is youngest?

a)

Inceptisols

b)

Entisols

c)

Mollisols

d)

Spodosols

28.

Which of the following contributes to food security?

a)

Acid rain

b)

Soil compaction

c)

Healthy soil

d)

Urban sprawl

29.

Soil supports plant growth by providing:

a)

All of the above

b)

Water

c)

Nutrients

d)

Air

30.

Which of the following is NOT a function of soil?

a)

Provider of sunlight

b)

Habitat for organisms

c)

Medium for plant growth

d)

Regulator of water

31.

Which soil is associated with volcanic ash?

a)

Ultisols

b)

Aridisols

c)

Andisols

d)

Vertisols

32.

The ClORPT acronym stands for:

a)

Climate, Organisms, Relief, Parent material, Time

b)

Clay, Organic matter, Rain, Peat, Temperature

c)

None of the above

d)

Chemical, Loam, Oxidation, Respiration, Parent material, Temperature

33.

The presence of clay in the B horizon is due to:

a)

Biological decay

b)

Physical pressure

c)

Bedrock fracture

d)

Translocation

34.

Which soil property most affects its ability to hold water?

a)

Texture

b)

pH

c)

Smell

d)

Color

35.

Which practice can harm soil structure?

a)

Cover crops

b)

Mulching

c)

Tillage

d)

Composting

36.

Leaching occurs primarily in:

a)

Wet climates

b)

Topsoil

c)

Urban roads

d)

Cold deserts

37.

The A horizon is characterized by:

a)

Red color

b)

High organic content

c)

Lava flow

d)

Unweathered rock

38.

Which component is NOT commonly recycled by soil?

a)

Phosphorus

b)

Plastic

c)

Nitrogen

d)

Carbon

39.

Which type of soil holds the most water but makes much of it unavailable to plants?

a)

Silty soil

b)

Sandy soil

c)

Loamy soil

d)

Clayed soil

40.

Why is soil water considered critical in terrestrial ecosystems?

a)

It supports photosynthesis only

b)

It prevents erosion during rainfall

c)

It enables most biological and chemical soil processes

d)

It provides oxygen to plant roots

41.

What defines the Available Water Capacity (AWC) of soil?

a)

Total rainfall minus runoff

b)

Field capacity minus wilting point

c)

Gravitational water plus percolation rate

d)

Capillary water plus hygroscopic water

42.

What physical property allows water to move through soil capillaries?

a)

Cohesion

b)

Adhesion

c)

Gravity

d)

Viscosity

43.

Which tool is typically used to measure soil water under low tension conditions?

a)

Neutron probe

b)

Gypsum blocks

c)

TDR (Time Domain Reflectometry)

d)

Tensiometer

44.

In the context of soil water potential, water moves from:

a)

Higher to lower potential (less negative to more negative)

b)

Negative pressure to positive pressure

c)

Lower to higher potential (more negative to less negative)

d)

High pressure to low solute concentration

45.

Which soil type typically has the highest Available Water Capacity (AWC)?

a)

Silty soils

b)

Loamy soils

c)

Sandy soils

d)

Clay soils

46.

What is the primary force responsible for water movement in unsaturated soil zones?

a)

Osmosis

b)

Gravity

c)

Capillarity and cohesion

d)

Evaporation

47.

What is the term for water held too tightly to soil particles to be used by plants?

a)

Saturation water

b)

Hygroscopic water

c)

Gravitational water

d)

Capillary water

48.

What type of soil water is most readily available for plant uptake?

a)

Hygroscopic water

b)

Gravitational water

c)

Capillary water

d)

Bound water

49.

The difference between field capacity and permanent wilting point is called:

a)

Gravitational water

b)

Hygroscopic water

c)

Soil moisture deficit

d)

Available water capacity

50.

Watersheds are defined as:

a)

Surface runoff systems

b)

Drainage basins flowing to a common outlet

c)

Forested areas

d)

Underground water reservoirs

51.

Capillary rise occurs when:

a)

Rain infiltrates soil

b)

Water drains into the aquifer

c)

Water evaporates from the soil

d)

Water moves upward from the water table

52.

Matric potential in soil water refers to:

a)

The pressure applied to roots

b)

The energy from gravitational force

c)

The energy from adhesion to soil particles

d)

The energy from solute concentration

53.

In soil water refers to:

a)

The pressure applied to roots

b)

The energy from gravitational force

c)

The energy from adhesion to soil particles

d)

The energy from solute concentration

54.

Field capacity is defined as:

a)

Water content after free drainage

b)

Permanent waterlogged condition

c)

The maximum amount of water soil can hold

d)

Water content during saturation

55.

The process of water movement through plants and its evaporation from aerial parts is called:

a)

Runoff

b)

Condensation

c)

Transpiration

d)

Infiltration

56.

Which soil texture holds the most total water but the least available water?

a)

Sand

b)

Loam

c)

Silt

d)

Clay

57.

Capillary action in soils is due to:

a)

Cohesion and adhesion

b)

Evaporation

c)

Percolation

d)

Gravity

58.

Which process contributes directly to groundwater recharge?

a)

Infiltration

b)

Runoff

c)

Interception

d)

Evapotranspiration

59.

Evapotranspiration is influenced by:

a)

All of the above

b)

Temperature

c)

Humidity

d)

Wind speed

60.

The major water loss from cropped land is due to:

a)

Drainage

b)

Leaching

c)

Runoff

d)

Evapotranspiration

61.

Soil profiles develop over:

a)

Days

b)

Years

c)

Months

d)

Centuries

62.

Soil's ability to reduce pollutants in water is called:

a)

Filtration

b)

Crystallization

c)

Acidification

d)

Capillarity

63.

Soil organic matter contributes primarily to:

a)

Water runoff

b)

Nutrient supply

c)

Pesticide application

d)

Rock formation

64.

Which soil is least weathered?

a)

Entisol

b)

Alfisol

c)

Oxisol

d)

Mollisol

65.

Vertisols are known for:

a)

Shrinking and swelling

b)

Sandiness

c)

Freezing

d)

Acidic pH

66.

The uppermost soil layer rich in organic matter is called:

a)

O horizon

b)

C horizon

c)

B horizon

d)

R horizon

67.

Soil that filters contaminants is performing which function?

a)

Biological

b)

Regulatory

c)

Supportive

d)

Structural

68.

Which of the following is a soil formation process?

a)

Illuviation

b)

Runoff

c)

Condensation

d)

Evaporation

69.

Which soil type shows freeze-thaw features?

a)

Gelisol

b)

Vertisol

c)

Ultisol

d)

Entisol

70.

Which is NOT a soil forming factor?

a)

Topography

b)

Organisms

c)

Climate

d)

Color

71.

What distinguishes soil health from soil fertility?

a)

Only structure

b)

Color

c)

Broad ecological function

d)

Only chemical makeup

72.

What do soil orders classify?

a)

Soil fertility

b)

Soil color

c)

Soil types by formation and properties

d)

Soil use

73.

Which is the best indicator of biologically active soil?

a)

Dark color

b)

Clay content

c)

Earthworm presence

d)

pH

74.

Which horizon is composed of unweathered rock?

a)

B

b)

O

c)

R

d)

C

75.

A healthy soil ecosystem includes:

a)

Only fungi

b)

Diverse organisms

c)

Only bacteria

d)

No organisms

76.

What role does soil play in the water cycle?

a)

It provides sunlight

b)

It absorbs and filters water before it enters rivers or aquifers

c)

It produces oxygen

d)

It breaks down rocks

77.

Which of the following is NOT a function of soil?

a)

Plant growth support

b)

Recycling nutrients

c)

Water regulation

d)

Provider of sunlight

78.

What does soil provide to support plant growth?

a)

Water

b)

Nutrients

c)

Air

d)

All of the above

79.

Which soil function is the most related to drinking water filtration?

a)

Providing structure

b)

Plant growth

c)

Recycling nutrients

d)

Water regulation

80.

Why is soil important for plant growth?

a)

It anchors roots and supplies water and nutrients

b)

It increases oxygen levels

c)

It reflects sunlight

d)

It breaks down rocks

81.

Which of the following is NOT a factor in the CLORPT model of soil formation?

a)

Pollution

b)

Organisms

c)

Parent material

82.

How does chemical weathering differ from physical weathering?

a)

Physical weathering changes the rock's chemical composition

b)

Physical weathering creates new minerals

c)

Chemical weathering breaks rocks using pressure

d)

Chemical weathering breaks down rocks using water and acids

83.

Which layer of a soil profile is typically richest in organic matter and biological activity?

a)

Subsoil

b)

Bedrock layer

c)

Parent material

d)

Topsoil

84.

What role does topography play in soil formation?

a)

It changes the temperature of the soil layers

b)

It adds organic matter directly to soil

c)

It influences water movement and soil accumulation or erosion

d)

It determines the mineral composition of soil

85.

Why is soil classification important in environmental science and agriculture?

a)

It helps find underground water

b)

It predicts weather conditions

c)

It helps determine soil color

d)

It guides land use decisions for farming, construction, and conservation

86.

What is a key benefit of good soil structure?

a)

Improves porosity and water infiltration

b)

Increases soil color intensity

c)

Lowers soil acidity

d)

Reduces soil temperature

87.

Which component combination makes up approximately 50% of the soil volume?

a)

Water

b)

Solids (minerals and organic matter)

c)

Minerals

d)

Air

88.

The USDA soil texture triangle is used to classify soil based on:

a)

Temperature and color

b)

Sand, silt, and clay proportions

c)

Organic matter and pH

d)

Water content and bulk density

89.

What does bulk density measure in soil?

a)

Mass of dry soil per volume

b)

Amount of nutrients

c)

Volume of air in pores

d)

Soil pH levels

90.

What is soil architecture primarily concerned with?

a)

The color and smell of the soil

b)

Soil acidity and salinity

c)

The spatial arrangement of soil particles and pores

d)

The mineral composition of soil

91.

Which of the following is not a typical cause of soil compaction?

a)

Rainfall on bare soil

b)

Cover crops

c)

Heavy machinery

d)

Livestock trampling

92.

What is the most effective practice to maintain good soil structure?

a)

Keeping soil uncovered after rainfall

b)

Compacting the soil before planting

c)

Frequent tillage

d)

Reducing tillage and adding organic matter

93.

What is the main function of macropores in soil?

a)

Facilitate drainage and air movement

b)

Store nutrients for plants

c)

Retain water for long periods

d)

Support microbial activity

94.

Which factor does not significantly affect soil temperature?

a)

Seasonal air temperature

b)

Moisture content

c)

Soil cover

d)

Soil texture

95.

In the Munsell color system, what does the "value" refer to?

a)

The lightness or darkness of the color

b)

The intensity of the color

c)

The mineral content of the soil

d)

The texture of the soil

96.

What does bulk density measure in soil?

a)

Clay content

b)

Water holding capacity

c)

Mass per unit volume including pore space

d)

Weight of soil solids

97.

Which soil color typically indicates high organic matter?

a)

Red

b)

Gray

c)

Dark brown

d)

Yellow

98.

Which term refers to the soil's ease of tillage and seedbed preparation?

a)

Structure

b)

Tilth

c)

Texture

d)

Porosity

99.

Which method is commonly used in the field to estimate soil texture?

a)

Water test

b)

Ribbon test

c)

Munsell test

d)

pH test

100.

What are the three primary soil particle types used to define texture?

a)

Clay, loam, peat

b)

Gravel, sand, silt

c)

Sand, silt, clay

d)

Silt, peat, humus

101.

Which process naturally improves soil structure?

a)

Biological activity

b)

Rainfall

c)

Plowing

d)

Freezing

102.

Which of the following improves soil aggregation?

a)

Waterlogging

b)

Excessive tillage

c)

Compaction

d)

Organic matter

103.

Which soil horizon is most likely to exhibit granular structure?

a)

B horizon

b)

A horizon

c)

C horizon

d)

R horizon

104.

Soil porosity is most affected by which two properties?

a)

Structure and depth

b)

Bulk density and pH

c)

Texture and structure

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