Soil Lec (2.1 & 2.4)

Question 1

the detachment and movement of soil or rock by water, wind, ice, or gravity to an area of deposition

Answer 1

Erosion

Question 2

the process of soil erosion involves

Answer 2

• detachment
• transportation
• deposition

Question 3

types of soil erosion

Answer 3

1. geological or natural erosion
2. accelerated erosion

Question 4

True or False

Accelerated Erosion is the erosion that is much more rapid than normal, natural, geological erosion.

Answer 4

True

Question 5

wearing away of the earth’s surface by water, ice or other natural agents under natural environmental conditions

Answer 5

Geological or Natural Erosion

Question 6

what are the steps in accelerated erosion

Answer 6

1. detachment
2. transportation

Question 7

Mechanics of the Soil Erosion Process

Answer 7

1. Soil detachment by Rainfall
2. Entrainment or transportation of sediments
3. Sediment deposition

Question 8

raindrops splash soil sediments from the soil surface into the runoff

Answer 8

Soil detachment by Rainfall

Question 9

kinetic energy formula

Answer 9

kinetic energy = 1/2 x mass x velocity²

Question 10

from upslope to downhill direction, whether in rills, between rills, and sheet flow

Answer 10

Entrainment or transportation of sediments

Question 11

the process of sediments settling out under the action of gravity

Answer 11

Sediment deposition

Question 12

the rate of sediment deposition depends on particle size, being ____ for sand and ____ for clay particles

Answer 12

rapid ; slow

Question 13

True or False

Crusting leads to more
runoff

Answer 13

True

Question 14

Types of Water Erosion

Answer 14

1. splash erosion
2. sheet erosion
3. rill and gully erosion
4. stream bank erosion

Question 14

• The particles are detached by the force of falling raindrops
• Causes breakdown of soil aggregates

Answer 14

Splash Erosion

Question 14

Soil particles are easily transported in a thin layer or sheet by flowing water

Answer 14

Sheet Erosion

Question 15

True or False

Gully erosion are small channels generally less than 2 inches deep

Answer 15

False

Correct answer: Rills

Question 16

Erosion that occurs along the banks of streams.

Answer 16

Stream Bank Erosion

Question 17

Factors Affecting Soil Erosion

Answer 17

1. rainfall
2. soil erodibility
3. vegetation cover
4. relief
5. human activities

Question 18

factors that affect rainfall erosivity

Answer 18

• frequency
• intensity
• distribution
• duration

Question 19

true or false

rainfall intensity is positively correlated to soil erosion if all other factors are held constant

Answer 19

true

Question 19

this is the climatic element that mainly affects erosion in the humid tropics

Answer 19

rainfall

Question 20

refers to the vulnerability or proneness of the soil to erosion

Answer 20

Soil Erodibility

Question 21

defined as the fineness or coarseness of soil particles

Answer 21

soil texture

Question 22

# True or False high clay content induces surface runoff and increases transportability but decreases detachability

Answer 22

True

Question 23

# True or False medium-textured soils (silt, silt loam, and loam) are **less erodible** than sandy or clayey textures

Answer 23

False | Correct answer: more erodible

Question 24

# True or False Soil erosion by raindrop impact is affected by the texture, which in turn also affects transportability

Answer 24

True

Question 25

# True or False A relatively high infiltration rate coupled with resistance to transport by runoff results in a **high erosion potential**

Answer 25

False | Correct answer: low erosion potential

Question 25

# True or False High sand content gives a coarse texture, which allows water to infiltrate readily, **reducing** runoff

Answer 25

True

Question 26

the arrangement of primary particles into aggregates

Answer 26

soil structure

Question 27

# True or False **soil structure** influences the infiltration rate and the movement of water in a soil

Answer 27

True

Question 28

* Promotes aggregation leading to increased infiltration rate * Binds soil particles to form water stable aggregates * Increases soil's WHC

Answer 28

organic matter

Question 29

# True or False Soil erosion increases at an increasing rate with increasing slope steepness while the amount of soil loss increases as the slope length increases

Answer 29

True

Question 30

# True or False As both slope length and gradient increase, the velocity and volume of runoff increases, and the erosion potential is magnified

Answer 30

True

Question 31

# True or False Highly permeable soils are **more prone** to erosion by water since they can absorb water effectively

Answer 31

False | Correct answer: less prone

Question 32

forms of wind erosion

Answer 32

1. detrusion 2. abrasion

Question 32

wind erosion is also known as ____

Answer 32

soil blowing

Question 33

the wearing away of rocks and soil projections by fine particles carried in suspension

Answer 33

detrusion

Question 34

# True or False **abrasion** forms the large rocks carved into grotesque shapes in deserts

Answer 34

False | Correct answer: detrusion

Question 35

takes place close to the ground where the moving particles are larger and bouncing along over the surface

Answer 35

abrasion

Question 36

Forms by which Materials are Carried Away

Answer 36

1. extrusion 2. efflution 3. efflusion

Question 37

rolling away by large particles

Answer 37

extrusion

Question 38

removal of very fine particles

Answer 38

efflution

Question 39

particles of intermediate size move off downwind into bouncing action called saltation

Answer 39

efflusion

Question 40

Types of Particle Movement by Wind Action

Answer 40

1. suspension 2. creep 3. saltation

Question 41

bouncing movement particles

Answer 41

saltation

Question 41

rolling movement particles

Answer 41

creep

Question 42

movement by very fine particles, mainly less than 0.1 mm diameter

Answer 42

Suspension

Question 42

Mechanical Measures/Control

Answer 42

1. riprap 2. terracing 3. bioengineering 4. sediment traps 5. retention ponds

Question 43

Erosion Control/Prevention Measures

Answer 43

1. Structural/Mechanical Measures 2. Cultural Measures 3. Vegetative control

Question 44

* Large angular rocks may be laid at the bottom or side of channels where high-water velocities may be expected * Designed to limit/prevent detachment of soil particles at the bottom or side of channels

Answer 44

riprap

Question 45

“Stairs-like” surface manipulation to reduce down-slope runoff velocity and encourage retention of sediments

Answer 45

Terracing

Question 46

Use of vegetation to protect channels, reduce runoff velocity and trap sediments

Answer 46

Bioengineering

Question 47

designed to slow down runoff and trap sediments

Answer 47

Sediment Traps & Sedimentation/Retention Ponds

Question 47

Cultural Measures

Answer 47

1. cover cropping 2. multiple cropping 3. mulching 4. conservation tillage 5. contour cultivation 6. addition of soil conditioners

Question 48

conservation tillage includes

Answer 48

1. minimum tillage 2. strip till 3. ridge till 4. no tillage system

Question 49

Planting of close growing grasses and legumes to cover and protect the surface of the soil

Answer 49

cover cropping

Question 50

When cover crops are plowed under and incorporated into the soil, cover crops may be referred to as ____

Answer 50

green manure crops

Question 51

involves either sequential cropping, the growing of 2 or more crops a year in a sequence, intercropping the growing of 2 or more crops in the same piece of land at the same time

Answer 51

Multiple Cropping

Question 52

Any material such as straw, sawdust, leaves, plastic film, loose soil, etc., that is spread or formed upon the surface of the soil to protect the soil and/or plant roots from the effects of raindrops, soil crusting, freezing, evaporation, etc.

Answer 52

mulch

Question 52

Any tillage sequence that reduces loss of soil or water relative to conventional tillage, which generally leaves at least 30% of the soil surface covered by residues

Answer 52

Conservation Tillage

Question 53

minimum use of primary and/or secondary tillage necessary for meeting crop production requirements under the existing soil and climatic conditions, usually resulting in fewer tillage operations than for conventional tillage

Answer 53

Minimum Tillage

Question 54

Preparation of seedbed by conditioning the soil along narrow strips in adjacent to seed rows

Answer 54

Strip Tillage

Question 54

A tillage system in which ridges are reformed atop the planted row by cultivation, and the ensuing row crop is planted into ridges formed the previous growing season

Answer 54

Ridge Tillage

Question 55

A procedure whereby a crop is planted directly into the soil with no primary or secondary tillage since harvest of the previous crop

Answer 55

No Till

Question 55

* Plowing, harrowing and furrowing across the slope of the land * Effective in minimizing soil erosion on gentle slopes

Answer 55

Contour Cultivation

Question 56

examples of soil conditioners

Answer 56

organic matter & lime/gypsum