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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)
https://gotoclass.tnecampus.org/d2l/le/content/8094442/viewContent/60403445/View 3/12
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)
https://gotoclass.tnecampus.org/d2l/le/content/8094442/viewContent/60403445/View 4/12
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)
https://gotoclass.tnecampus.org/d2l/le/content/8094442/viewContent/60403445/View 5/12
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)
https://gotoclass.tnecampus.org/d2l/le/content/8094442/viewContent/60403445/View 7/12
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)
https://gotoclass.tnecampus.org/d2l/le/content/8094442/viewContent/60403445/View 10/12
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)
https://gotoclass.tnecampus.org/d2l/le/content/8094442/viewContent/60403445/View 11/12
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)
https://gotoclass.tnecampus.org/d2l/le/content/8094442/viewContent/60403445/View 12/12
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