Soil & Water Conservation Exam 2 Perterson

Front 1

What conditions are required for soil erosion by wind to take place?

Back 1

1. soil is loose, finely divided & dry
2. soil surface is smooth & bare
3. wind is strong

Front 2

Where is soil erosion by wind important in the United States?

Back 2

dryland

also seacoasts and de-vegetated land

Front 3

Describe "suspension"

Back 3

particles & aggregates <0.05 cm (silts & clays)
dust particles kept in air until it rains or the wind slows.

Front 4

Describe "Saltation"

Back 4

fine to medium sands, 0.5mm>sands>0.05mm
Grains jump and knock into other soil particles, increasing the number of grains in suspension & surface creep - MOST IMPORTANT!

Front 5

Describe "surface creep"

Back 5

soil grains >0.5
cannot be lifted into suspension, but bump along the surface.

Front 6

List the types of damage caused by soil erosion from wind.

Back 6

Loss of soil
Textural change
nutrient losses
productivity losses
abrasion (to vehicles, structures, etc)
Air Pollution

Front 7

What is Zo? What is D? What determines their height in a particular situation?

Back 7

D= zero plane displacement caused by vegetative cover
Zo= roughness parameter

Front 8

What is Zo? What is D? What determines their height in a particular situation?

Back 8

Zo is the height at which the wind velocity = Zero

D= distance which vegetative cover extrapolates the wind velocity to zero (eg, ~distance from ground to tops of plants)

Front 9

Why is a rough soil surface usually less erodible than a smooth surface, as related to soil erosion by wind?

Back 9

Wind flows faster over smoother surfaces
& Initial rolling is important for the grain to pick up speed and lift off the ground.

Front 10

What is the threshold velocity of a wind?

Back 10

the velocity required to casue wind erosion
- dependent on soil/surface properties
from 8-30 mph, measured 6" above surface.

Front 11

What is avalanching and why does it occur?

Back 11

The increasing rate of erosion as wind blows across a field.
WHY?
1. accumulation of eroded material from previous storms
2. Increasing quantity of saltation particles.
3. Smoother surfaces.

Front 12

What are the 6 major factors affecting the amount of erosion from wind?

Back 12

1. Soils resistance to erosion
2. Surface Roughness
3. Rainfall
4. land slope (hummocks/knolls: lumpy terrain)
5. length of exposed area
6. Vegetative cover

Front 13

How do knolls affect soil erosion by wind?

Back 13

Increase!
Layers of higher wind velocities crash into the peaks of the knolls- greatest erosive force on crests!

Front 14

What are the three principles of controlling soil erosion by wind?

Back 14

1. Reduce wind velocity near surface to below threshold velocity
2. Remove abrasive materials from wind stream
3. reduce soil erodability

Front 15

What practices can be used in SOIL SURFACE to reduce soil erosion by wind?

Back 15

Ridges trap eroding soil grains in furrows when perpendicular to wind direction

Front 16

What practices can be used in SOIL WATER to reduce soil erosion by wind?

Back 16

moist soil isn't eroded by wind
moist soil is good for plants...plants also help cohere soil aggregates.

Front 17

What practices can be used in FIELD LENGTH to reduce soil erosion by wind?

Back 17

The shorter the slope length, the fewer grains of soil can be picked up by the wind.

Front 18

What practices can be used in VEGETATION to reduce soil erosion by wind?

Back 18

vegetative cover increases the thickness of the still air layer nest to the soil.

Front 19

What are the major uses of the wind erosion prediction equation?

Back 19

tool for conservation plans
assess current conditions & plan changes on CULTIVATED FIELDS, primarily in the eastern US

Front 20

What are the factors used to predict soil erosion by wind (E)?
Hint: There are 5.

Back 20

I' = erodability
K' = soil ridge roughness
C' = climate (%--> fraction)
L' = Length of field (ft)
V' = vegetative cover

Front 21

What are some of the expanded uses of the wind erosion prediction equation & What special concerns are there with each of these?

Back 21

HUMID REGIONS: WEG 1 had to be broken down into 5 (group converts to I')
RANGELAND:ned to use special V values (determined by range species & vegetation)
AIR POLLUTION PREDICTION:multiplies E values by .003 to calculate suspended dust
OTHER COUNTRIES:K', C' and R' require extra consideration/amendements.

Front 22

What are some significant limitations of the original wind erosion equation (WEQ)?

Back 22

Assumes homogeneous conditions downwind.
C' is difficult to apply outside of the US great plains. (Garden City, KS reference)
Doesn't work in frozen, high altitude areas.
***Doesn't account for complex variables and their relationships!!

Front 23

How is the approach of the wind erosion prediction system (WEPS) completely different from the wind erosion equation?

Back 23

Model based, not empirical-->describes/simulates actual process
Can split fields into sub-regions
Can predict erosion from a single storm (& probability of the storm)
Continuous, daily

Front 24

What soil loss is "tolerable" (T-value)?

Back 24

Tolerable: allows continuous cropping & productivity

Front 25

What factors determine the "Tolerable" soil loss amount?

Back 25

PPP:
parent material
productivity of soil & subsoil
previous erosion

Front 26

Why is the use of T values a controversial issue?

Back 26

Some think that they are too high when considering social goals and soil's physical properties.

Some think that they are too low for practical purposes & historic profitability of previous practices.

Organic soils lost to drainage of wetlands are not calculated in.

Doesn't account for soil movement within a field.

Front 27

In what cases might the "tolerable soil loss" value be too high?

Back 27

T values cannot always match the soil formation rate, and some plants are more sensitive to abrasion.

Front 28

What is the Universal Soil Loss Equation? Write the equation and briefly describe each factor including the units.

Back 28

A= RKLSCP
R: Rainfall
K: soil erodability
LS: slope steepness & length
C: Cover mngt
P: support practices

Front 29

What is the range of the Runoff and Erosion Factor (R value) for the USLE in the United States?

Back 29

20-550 ft-ton/ac-yr

(Hawaii: 125-450)

Front 30

What were the five crop stage periods used to determine the Cover-Management (C value) Factor in USLE?

Back 30

Rough Fallow
Seedling
Establishment
Maturing Crop
residue/stubble

Front 31

What methods can be used to reduce the Supporting-Practice Factor (P value) in USLE?

Back 31

contour
contour strip cropping
terracing

Front 32

What do each of the following mean as related to the Support-Practice Factor in USLE: Pc, Ps, and Pt?

Back 32

Pc: contour
Ps: contour strip cropping
Pt: terracing

Front 33

Summarize the important changes in R value made in the Revised Universal Soil Loss Equation (RUSLE) as compared to the USLE.

Back 33

Covered all of US, minus Alaska

Front 34

Summarize the important changes in LS value made in the Revised Universal Soil Loss Equation (RUSLE) as compared to the USLE.

Back 34

Could now calculate from multi-segment slopes

Front 35

Summarize the important changes in C value made in the Revised Universal Soil Loss Equation (RUSLE) as compared to the USLE.

Back 35

Now 6 periods based on cover, rather than a fixed crop type (more crop types)

Front 36

Summarize the important changes in P value made in the Revised Universal Soil Loss Equation (RUSLE) as compared to the USLE.

Back 36

Only Pt (terracing) changed; now reduced slope length and deposition credits & considered the slower water velocities.

Front 37

What does WEPP stand for?

Back 37

Water Erosion Prediction Project

Front 38

How is the WEPP approach different than the USLE or RUSLE approach?

Back 38

Physics based computer model incorporating weather models, etc.
Predicts spatial & temporal soil loss

Front 39

Describe the two versions of WEPP.

Back 39

Hillslope: for a single slope
Can determine erosion for a single storm, erosion/deposition at any spot on the slope, assesses individual periods of a crop rotation & used on non-uniform slopes

Watershed: calculates several profiles leading to a small channel (not for large channel)
Computes sediment delivery, transport and deposition in a small channel/impoundment (reservoir)

Front 40

What will WEPP be able to do which is impossible with RUSLE?

Back 40

Calculates the amount of soil eroded & when and where it is deposited.

Predicts spatial & temporal soil loss &uses weather models.

Front 41

Describe the uses, effects on the soil, effects on surface residue, and effects on soil erosion of the moldboard plow.

Back 41

turns over the soil- inverts it.

Buries plants & requires the most power to use.
Bad for erosion

Front 42

Describe the uses, effects on the soil, effects on surface residue, and effects on soil erosion of the tandem disk.

Back 42

used for light secondary tillage
aka "double disk": one disk turns the soil out, the second disk puts the soil back.
Covers part of crop residues.

Front 43

Describe the uses, effects on the soil, effects on surface residue, and effects on soil erosion of the one-way disk.

Back 43

large disks bury crop residues and leave a smooth surface- bad for erosion

Front 44

Describe the uses, effects on the soil, effects on surface residue, and effects on soil erosion of the drag harrow.

Back 44

used to break clods & smooth surface after plowing (like a rake)- good for seed bed prep

Front 45

Describe the uses, effects on the soil, effects on surface residue, and effects on soil erosion of the chisel plow.

Back 45

ripping implement- penetrates deep into spoil to cut weed roots

Used in conservation tillage

Front 46

Describe the uses, effects on the soil, effects on surface residue, and effects on soil erosion of the rotary hoe.

Back 46

many rimless wheels incorporate all of the surface residue into the soil. Breaks soil crust, kills small weeds & smooths surface.

Also used in small gardens at small scale.

Front 47

Why do some farmers prefer to seed into ridge tops rather than into furrows or flat seed beds?

Back 47

Dry- seed in the furrow
Wetter- seed on the ridges (more common with hand cultivation.) - this results in fewer nutrients leaching from the soil too.

Front 48

Give a definition of conservation tillage.

Back 48

leaves >30% surface residue after planting

Front 49

What is stubble mulch tillage?

Back 49

tillage that purposely retains surface stubble for erosion reduction

Front 50

What are some reasons many farmers have had lower yields with stubble mulch tillage?

Back 50

Weeds.
poorer seedbed quality
delayed growth due to slow spring warm-up
reduced available nitrogen

Front 51

What are some advantages and problems with reducing preplant tillage for corn production?

Back 51

slow spring warm- lower yields

Front 52

What are some estimates of conservation tillage use in the future? What are some problems with such estimates?

Back 52

farmers estimates of current practices are overly generous...55% believed they were using conservation tillage while <5% actual.

Front 53

Under what conditions does deep plowing seem to be most beneficial?

Back 53

when a productive soil has been covered by unproductive sediments, eg sandy, highly erodible soils.

Front 54

Describe the benefits of contour tillage.

Back 54

25-76% reduction in water erosion
another estimate: 40-80% reduction. Increase yields
More moisture, less eroded/more productive soil, less washing out of seeds or burying of seedlings.

Front 55

Give some suggestions for effective farming fields planted on the contour.

Back 55

Use a guideline to start and plow a furrow on either side & mark with stake. Furrows should direct excess water to grassed waterways

Front 56

Why is managing soil organic matter levels is so important?

Back 56

organic matter improves soil structure, managing for soil carbon can enhance productivity and environmental quality, and can reduce the severity and costs of droughts, floods, and diseases.

Also Reduces atmospheric CO2.

Front 57

Why does focusing on managing soil organic matter (or soil carbon) more effectively control soil erosion than our present focus on T-values.

Back 57

To address these environmental goals and maintain the land’s productive potential, we must now go beyond erosion control and manage for soil quality.

How soil functions on every inch of a farm, not just in buffers or waterways, affects erosion rates, agricultural productivity, air quality, and water quality. The most practical way to enhance soil quality today is to promote better management of soil organic matter or carbon.

Front 58

What soil management practices help build soil organic matter?

Back 58

cover crops, crop rotations, and reduced tillage

Front 59

What are small grains and how do they affect erosion?

Back 59

Rice, wheat, oats, rye, etc.
Broadcast planted.

Dense stand & earlier growth mean less erosion than row crops.

Front 60

What are row crops and how do they affect erosion?

Back 60

Most profitable crops (corn soy, sugar beets, cotton, etc)
rows spaces 40" apart for cultivation.

Erosion can be very high.

Front 61

What are forage crops and how do they affect erosion?

Back 61

pasture & hay
Densely planted, untilled (perennial)
Soil BUILDING.

Front 62

What are tree crops and how do they affect erosion?

Back 62

nuts, apples, lumber

Trees with undergrowth or high litter have protected soils, while "Clean cultivated" orchards are subject to high erosion.

Front 63

How does the following affect soil erosion: plant population?

Back 63

more crops/acre--> less erosion

up to 28K/acre, rather than the traditional 12K

Front 64

How does the following affect soil erosion:row spacing.

Back 64

wider rows and spacing increase erosion
20"-30" better than 40"
cools plants & can increase yields too.

Front 65

How does the following affect soil erosion:soil fertility

Back 65

fertile land can reduce erosion to half of what infertile land does.

Front 66

How does the following affect soil erosion: seasonal changes in plant cover?

Back 66

most erosion right after new crop planted, less after crop is established

Perennial crops can have increased erosion after cut or if overgrazed

Front 67

What can be done in row crop monocultures to reduce soil erosion?

Back 67

limit these systems to suitable soils
plant narrow with enough fertilizer & lime & drainage
Cover during the off-season.(protects from erosiona nd return organic matter to the soil)

Front 68

What is a crop rotation? What are some benefits of crop rotations compared to monocultures? What are some problems?

Back 68

2 or more plants grown on same land
Control erosion & plant diseases, insects & weeds specific to one plant
More organic matter of different kind is beneficial

Schedules soemtimes need to be adjusted
Must achieve balanced productive soil capabilities

Front 69

Green manure?

Back 69

plowing forage into soil to increase its structure, OM, permeability (can use cover crop or remnants of a forage crop)

Legumes best for N.

Front 70

companion crop?

Back 70

small grain & forage planted together

Front 71

Cover crop?

Back 71

fills the gaps where the other crop would leave the ground bare.

Front 72

Sequential cropping?

Back 72

a multiple cropping system where a crop rotation is compressed into 1 year.

Front 73

Intercropping?

Back 73

Multiple cropping where 2 or more crops are grown on the same feild at the same time

eg corn w/ soy between rows- lowers erosion and maximizes production

Front 74

What is the difference between the following types of stripcropping: contour, buffer, field, and wind?

Back 74

CONTOUR: grown around a hill on the contour
BUFFER: protective strips vary in widths to accommodate irregular slopes
FIELD:used on irregular rolling land- cross general slopes but don't match contours
WIND: protective strips laid out Perpendicular to prevailing winds

Front 75

border strip?

Back 75

vegetation along a stream, farmstead of field to protect from erosion.

RF streams: 75 ft from navigable waterways.

Front 76

barrier strips?

Back 76

narrow strips of protective crop laid out perp to prevailing wind- similar to "wind strip cropping" but better for grasses & small areas

Front 77

Why is evaluation of a soil's productive potential difficult?

Back 77

Must consider weather, management & soil potential

*some items harder to measure.

Front 78

What are some important considerations in evaluating cropping systems?

Back 78

soil loss
soil productivity potential
soil structure
Environmental effects of the cropping system