The Cost of Soil Erosion
Rick Cruse
Scott Lee
Iowa State University
Different days, different locations, 2014
IOWA
2013
Soil erosion?
• Is economically viable
• Is not economically viable
• Will always occur on farmed land at
unsustainable levels
• Cannot be stopped
• Has greater off site costs than on site costs
How does soil erosion impact $$$
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•
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Crop yield
Soil fertility
Water quality
Flooding
▫ Loss of upland water storage
▫ Reduction in flood plain storage
▫ Reduction in reservoir storage
What is value of 1Ton topsoil saved?
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•
•
•
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$0.50
$1.00
$10.00
$25.00
$50.00
$100.00
Rathbun Lake Watershed Project*
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•
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354,000 acre watershed
$24 million invested since 2006
Sediment loss reduced > 41,000 Ton/yr
P loss reduced > 175,000 lbs
*Des Moines Register, June 15, 2014. Jason Clayworth.
Rathbun Lake Watershed Project
• Since 2006 cost is ~
• $83/ton soil
• $237/lb P
Goal
• Identify erosion impact on crop yield & $$$
Identify erosion impact on yield
• HOW?
S. Jagadamma, R. Lal, and B.K. Rimal. 2009. Effect of topsoil depth and soil amendments on corn yield and properties
of two Alfisols in central Ohio. J. Soil and Water Cons. 64:70-80.
Approach
• Identify topsoil depth impact on yield
• Identify change of topsoil depth since agriculture
began in Iowa
• With the Iowa Daily Erosion Project v.2 identify
change in topsoil depth that is occurring real
time (actually close to real).
What is past erosion costing us?
• Erosion has caused what change in topsoil
depth?
• What is crop yield response to topsoil depth?
• Over what area are crops being produced?
• What is the market value of the commodity?
How much soil has eroded?
How much soil has eroded
• Use average NRI estimate since 1982 (5.5
T/A/YR)
▫ Assume erosion rate for last 150 years
▫ Sheet and rill only
▫ Adjusted for ephemeral gullies
• 150 yrs farming – 6.8 inches soil
What is crop yield response to topsoil depth?
A horizon thinning 6.8 inches -> 5 & 11 bu/A
(Bu/A)
Yield (Bu/A
2.0
4.0
Depth
(in)
8.0
6.0
Blackhawk County. 6.8 inch soil thinning
19 bu/A
TSD vs. Normalized Yield: Corn
1.00
Normalized Yield
0.80
0.60
0.40
0.20
4.0
9.0
14
19
TSD (in)
Marshall County. 6.8 inches soil thinning -> 18 bu/A
Mitchell County. 6.8 inches topsoil loss 
18 bu corn/A
Corn Yield vs Topsoil Depth
1.00
0.90
0.80
0.70
% Max Yield
0.60
0.50
0.40
0.30
0.20
0.10
0.00
0.0
5.0
10.0
15.0
2008 (24 in)
Linear (2008)
20.0
TSD (in)
25.0
2010 (30 in)
Linear (2010)
30.0
35.0
40.0
2012 (14 in)
Linear (2012)
Mitchell County. 6.8 inches topsoil loss  29 bu corn/A in 2012
David B. Lobell, Michael J. Roberts, Wolfram Schlenker, Noah Braun, Bertis B. Little, Roderick M. Rejesus, and Graeme L.
Hammer. 2014. Greater sensitivity to drought accompanies maize yield increase in the U.S. Midwest. Science. 344:516-519.
From where does $1 Billion come?
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Average soil loss 6.8 inches
Average corn yield loss 10 bu/A
Assume 20 million acres of corn
Assume market of $5.00/bu
10 bu/A X 20 million A X $5.00/bu = $1 Billion
http://www.desmoinesregister.com/story/money/agriculture/2014/05/03/erosion-estimated-costiowa-billion-yield/8682651/
How much does erosion cost $/A/Yr?
• $1 billion
• 150 years
• 20 million acres
$0.33/A/Yr
What is value of 1Ton topsoil saved?
•
•
•
•
•
•
$0.50
$1.00
$10.00
$25.00
$50.00
$100.00
Rathbun Lake Watershed Project
• Since 2006 cost is ~
• $83/ton soil
• $237/lb P
Annual cost impact are constant.
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•
•
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Each year lose permanently $1.00 production
Production loss is cumulative
Year 1 erosion occurs
Year 2 cost $1.00 from year 1 erosion = $1.00
Year 3 cost $1.00 from yr 1 + $1.00 = $2.00
Year 4 cost $1.00 from each previous year =
$3.00
• Year 5 cost $4.00
• Year 6 cost $5.00
Cumulative Cost Increases with Time
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Year 1 - $0.00 = $0.00
Year 2 - $1.00 (yr 1) = $1.00
Year 3 - $1.00 (yr 2) + $2.00 (yr 3)= $3.00
Year 4 - $1.00 (yr 1) + $2.00 (yr 3) + $3.00 = $6.00
Year 5 - $6.00 + $4.00 = $10.00
Year 6 - $10.00 + $5.00 = $15.00
Year 7 - $15.00 + $6.00 = $21.00
Cost or
Return on Investment
$1,200.00
$1,000.00
$800.00
Cumulative loss
$600.00
Cumulative
Conservation
Investment
$400.00
$200.00
$0.00
1
3
5
7
9 11 13 15 17 19
Years of Farming Land
Conservation investment of $40/A/YR; Soil loss = $1.00/T
Cost or
Return on Investment
$3,500.00
Soil Value $0.50/Ton
$3,000.00
$2,500.00
$2,000.00
$1,500.00
$1,000.00
$500.00
$0.00
1
3
5
7
9
11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49
Years
Cumulative loss
Cumulative Conservation Investment
Summary
• Soil off site impacts seem economically more
important than on site yield economic impacts
• Return on conservation investment takes TIME!
• Soil conservation expenses for renters seldom
will be recovered
Challenges we face
• What evidence exists that we are on a
functionally sustainable path?
• If not on a sustainable path do we have a vision
of what that path is?
• Do we have the political will to address the
causes rather than the symptoms of our current
problems?
Ag Realities
• Agriculture if morphing to Agribusiness
▫ Fewer farmers control more
▫ Enterprise size is increasing
▫ Culture is multidimensional, business is less so
• Farming is very competitive
• Successful farmers make money
Ag Realities
 Voluntary conservation approaches work best
when incentives and benefits are aligned
• Majority of harvested land is rented
▫ Conservation incentives and benefits are not
well aligned
• Markets are farmed, not the land
Ag Realities
• Very strong ag and industry lobby
▫ Rationally not aligned with conservation goals
▫ Aligned with $$$ for individual industry
• Major policy elements not well aligned with soil
conservation and water quality
• Soil erosion science is weak
Frequency
Ag Realities
Conservation
Exploitation
What’s New
• Increased watershed focus
• Industry recognition of sustainability issues
• Food industry talking the talk – will they walk
the walk?
• Farmers vocalizing the ‘R’ word
• Increased emphasis on cover crops
What’s not new
• Specialization
• Loss of cultural based management skills and
increasing reliance on technology
• Growth in size of operations and equipment
What’s not new
• Government policy in conflict with conservation
• Degradation of soil and water resources
Elements of a fix
• Goal and a Plan
▫ Commitment to those goals
▫ Agriculture and agribusiness are different and
must be treated as such
• Policies
▫ That do not put conservation committed farmers
at a competitive disadvantage
• Address the problem, not the symptom
▫ Exploitation at expense of conservation