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3/29/2020 Soil Erosion (Chapter 17) Notes - AGRI1050R50: Introduction to Soil Science (2020S)

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Soil Erosion (Chapter 17) Notes

Soil Erosion (Chapter 17) Notes

Did you know .... Did you know that worldwide in the last fifty years, we have lost 12.4 billion acres of soil in land degradation? Chapter 17 highlights soil erosion from land degradation rates and causes, water eorsion as well as wind erosion, and means of mitigating these losses.

Lecture content notes are accompanied by videos listed below the notes in each submodule (e.g. Soil Erosion (Chapter 17) Videos A thru E). Print or download lecture notes then view videos in succession alongside lecture content and add additional notes from each video. The start of each video is noted in parenthesis (e.g. Content for Video A) within each lecture note set and contains lecture content through the note for the next video (e.g. Content for Video B).

Figures and tables unless specifically referenced are from the course text, Nature and Property of Soils, 14th Edition, Brady and Weil.

Content Video A

Soil Erosion

http://colbydigssoil.com/

Significant Problem Land Degradation – reduced productive potential

5 billion hectares (12.4 billion acres)

Desertification

Soil Degradation

Deforestation

AGRI1050R50: Introduction to Soil Science (2020S) LH

3/29/2020 Soil Erosion (Chapter 17) Notes - AGRI1050R50: Introduction to Soil Science (2020S)

https://gotoclass.tnecampus.org/d2l/le/content/8094442/viewContent/60403445/View 2/12

Downward Spiral

3/29/2020 Soil Erosion (Chapter 17) Notes - AGRI1050R50: Introduction to Soil Science (2020S)

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Erosion Erosion – gradual destruction or wearing away

Detachment, Transport, Deposition

Wind, Water, Ice, Other ‘Geologic Agents’

Geologic Erosion – wearing away of Earth’s surface

Natural – Leveling process

Allows for soil formation

Accelerated Erosion – Human induced

Highly destructive

Accelerated Erosion 10 to 1000X as destructive as geological

Huge problem worldwide – Cropland

Africa Asia South America – Lose 30-40 Mg/ha/year

3/29/2020 Soil Erosion (Chapter 17) Notes - AGRI1050R50: Introduction to Soil Science (2020S)

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Africa, Asia, South America Lose 30 40 Mg/ha/year

US – Lose 12 Mg/ha/year (7 water and 5 wind)

Undisturbed grasslands and Forests – 0.1 Mg/ha/year

Content Video B

Effects of Accelerated Soil Erosion On-Site Damage

Loss of fertility – Top soil – Upper layers soil

SOM and clays and silts lost

Loss soil structure, infiltration rates

Loss of rooting zone soil – closer to bedrock

Off-Site Damage

Fine particles – silt and clay

Moves nutrients, pesticides, pathogens, heavy metals, etc.

Sedimentation

Sedimentation

Sediments transport:

Nutrients - Eutrophication

Pesticides – Non-target harm

Pathogens – Contact recreation

Metals and Organics – Bioaccumulation and Toxicity

Biological

Turbidity – Cloudy Water

Changes temperature, interferes with photosynthesis

Clogs fish gills

Smothers Eggs

Physical

Changes natural flow path water

Fills stream channels and ditches, reservoirs and dams

Requires dredging to keep things moving

Off-Site Wind Erosion

3/29/2020 Soil Erosion (Chapter 17) Notes - AGRI1050R50: Introduction to Soil Science (2020S)

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Fine particles – Easy to move with wind

Sedimentation issues too

Destructive

Equipment and Physical Structures

Plants as well

Particulate Matter – size classifications

PM 10 – 2.5 to 10 microns

Ag and construction

PM 2.5 - <2.5 microns

Engine Exhaust

Smoke

Industrial Exhaust

Air Quality Standards: 160 ug/mg3 PM10 and 35 ug/mg3 PM 2.5

TN Erosion

http://www.nrcs.usda.gov/Internet/NRCS_RCA/reports/nri_eros_tn.html

What do these values mean? 1 acre, 6‐inches deep ~ 2,000,000 lbs.

Thus, 6 inches ~ 1,000 tons of soil

1 inch of soil over an acre = 167 tons

16.7 tons/acre/year = 0.1 inch soil loss

TN ~11 million acres farmland

Almost half TN land area

Significant loss annually

Once gone, its gone – especially our fertile loess soils of West Tennessee

https://www.tn.gov/agriculture/publications/farmfacts.pdf

Soil-Loss Tolerance T-Value

Maximum amount of soil that can be lost annually and indefinitely by the combination of water and wind erosion without degrading the soils long term productivity.

3/29/2020 Soil Erosion (Chapter 17) Notes - AGRI1050R50: Introduction to Soil Science (2020S)

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5 – 11 Mg/ha/yr (~5 tons/acre/yr)

~0.9 mm depth/year

Rate at which loss and creation are at least equal

Content Video C

Mechanics of Water Erosion Three Step Process:

Detachment

Transportation

Deposition

Raindrops – Destructive Force

Size and Velocity

Bare Soil vs Covered Soil

Rainfall > Infiltration rates – Water pond and move

Water Erosion

Sheet Erosion Uniform across soil surface

1/10 meter scale

3/29/2020 Soil Erosion (Chapter 17) Notes - AGRI1050R50: Introduction to Soil Science (2020S)

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Rill Erosion Volume of water increased – flows in channels

Meter scale

Easy to see in field

Gully Erosion Major flow path – creates gully or channel

Disrupts ag utilization plans

RUSLE - Revised Universal Soil Loss Equation Revised Universal Soil Loss Equation

A = R x K x LS x C x P

A – Predicted annual soil loss

R – Rainfall Errosivity

K – Soil Erodability

L – Slope Length

S – Slope Gradient or Steepness

C – Cover and Management

P – Erosion-control Practices

RUSLE Factors R – Rainfall Erodability Factor

Driving Force of Rain – Energy of the event

High Values (up to 700) – Humid Regions w/ big storms and lots of water – Gulf

Coast

3/29/2020 Soil Erosion (Chapter 17) Notes - AGRI1050R50: Introduction to Soil Science (2020S)

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Lower values (100s) – Pacific Northwest – lots of rain, but comes slow and

over time

K – Soil Erodability Factor

Susceptibility to erosion

Infiltration Capacity – > Infiltration, < Runoff Capacity

Soil Structure – > Structure, < Erosion

Higher Values – More susceptible

LS – Topographic – Length and Slope

Relative Value – Reference of 72 ft. with 9% slope

Steep Slopes/Short Distances – High values

Low Slopes/Long Distance – Low Values

C – Cover and Management

Type and kind of ground cover

Bare soil (tillage), active ground cover (cover crops, pasture, etc.) or

residue (no-till)

Management controlled

Bare soil = 1

P – Support Factors

Management Factor

Utilize terraces?

Plant against slope to slow down water movement?

GOAL – A < T

Predict soil loss

Manage soils (cropping systems, cover crops, management practices, etc.) to

reduce this loss

Goal is for loss (A) to be less than T (Soil Loss Tolerance)

Content Video D

Water Erosion Control Goal – Increase infiltration rates and reduce water runoff

Vegetative Cover

Mechanical Support

Conservation Tillage – Range of management practices

Maintain at least 30% of crop residues on surface

Technological Advances

Chemical weed and insect control

Machinery to plant into residue

Conservation Tillage Classifications

3/29/2020 Soil Erosion (Chapter 17) Notes - AGRI1050R50: Introduction to Soil Science (2020S)

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United States Conservation Tillage

Conservation Tillage

3/29/2020 Soil Erosion (Chapter 17) Notes - AGRI1050R50: Introduction to Soil Science (2020S)

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Content Video E

Wind Erosion Affects 12% of Continental US

8% Moderate

2% Severe

6 Great Plain States – Wind > Water Erosion

Arid and Semi-Arid Regions Issue

Mechanics

Detachment , Transport, Deposition

Saltation – Bouncing of particles along soil surface

Suspension – Particles get up into the atmosphere

3/29/2020 Soil Erosion (Chapter 17) Notes - AGRI1050R50: Introduction to Soil Science (2020S)

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WEQ - Wind Erosion Prediction Equation Wind Erosion Prediction Equation

E = f ( I x C x K x L x V)

I – Soil Erodability Factor

C – Climate Factor

K – Soil-Ridge Roughness Factor

L – Width of Field Factor

V – Vegetative Cover Factor

WEC Factors I – Soil erodability factor

Soil properties and degree of slope

C – Climate Factor

Wind velocity, soil temperature, precipitation

K – Soil-Ridge Roughness Factor

Clotiness of soil structure

L – Width of Field Factor

Length of travel of prevailing wind

V – Vegetative Cover Factor

Degree and nature of vegetative cover

Wind Erosion Control Moisture – moisture keeps the soil particles adhered to themselves

Cover – Bare soil is more prone to wind loss

Tillage Practices - try not to till when too dry

Barriers – Wind breaks

3/29/2020 Soil Erosion (Chapter 17) Notes - AGRI1050R50: Introduction to Soil Science (2020S)

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Reflect in ePortfolio Download Print

Conservation Reserve Program Government program – reduce soil loss

Takes marginal or highly erodible land out of row-crop production

Plant grass and/or trees – undisturbed land

Lease 10-15 years

Erosion Control – Review Global Issue

Management Issue – Lots of High Quality Solutions

Keep the soil covered!

Promote high infiltration rates!

Goal – Reduce Soil Loss

Loss (A) to be less than T (Soil Loss Tolerance)

Task: View this topic

Activity Details