The Cost of Soil Erosion to Iowa
Rick Cruse
Scott Lee
Iowa State University
Different days, different locations, 2014
IOWA
2013
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
• Loss of recreation opportunity
Soil erosion
• A. Is economically viable?
• B. Is not economically viable?
• C. Will always occur on farmed land at
unsustainable levels?
• D. Cannot be stopped?
• E. Has greater off site costs than on site costs?
What is value or cost of 1 ton of topsoil?
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•
•
•
•
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A.
B.
C.
D.
E.
F.
G.
$0.50
$1.00
$10.00
$25.00
$50.00
$100.00
>$100.00
Rathbun Lake Watershed Project*
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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
What is value or cost of 1ton of topsoil?
•
•
•
•
•
•
•
$0.50
$1.00
$10.00
$25.00
$50.00
$100.00
>$100.00
Goals
• What is soil erosion costing the producer?
• Create Midwest soil erosion inventory
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.
But what if soil thinning is due to
erosion, not artificial topsoil change?
What is past erosion costing us?
• Erosion has caused what change in topsoil
depth?
• What is the relationship between crop yield and
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
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
How much does erosion cost $/A/Yr?
• $1 billion
• 150 years
• 20 million acres
$0.33/A/Yr
What is value or cost of 1 ton of topsoil?
$0.33/5.5 T/A/Yr = $0.06/T
What is value or cost of 1ton of topsoil?
•
•
•
•
•
•
•
A.
B.
C.
D.
E.
F.
G.
$0.50
$1.00
$10.00
$25.00
$50.00
$100.00
>$100.00
Daily Erosion Estimation
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Conclusions
• Cumulative soil erosion is costing Iowa
substantial $$$
• Difficult to justify soil conservation on SHORT
TERM crop production effects
• Stay tuned for IDEP2 release
▫ Greater precision that IDEP1
▫ Better accuracy