Switchgrass Production in the Chariton Valley, Iowa Impacts on Soils

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Switchgrass Production in the Chariton Valley,
IowaImpacts on Soils Landscapes

• Lee Burras, Julie McLaughlin, Marty Braster, John
  Sellers, Charlie Brummer
• Iowa State University Chariton Valley RCD
• ORNL BFDP Cooperators Meeting, Memphis
• November 08, 2001

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Outline

• Objectives
• Site overview
• Methods
• Review of project significant conclusions
• Future needs
• Summary
• As questions come up, please ask.

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Who does and has done the real work for ISU?

• Julie McLaughlin,
• Research Associate, ISU

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General Research Objectives

• Quantify soil carbon contents (OC) across
  landscapes under common land uses in the Chariton
  Valley.
• Examine soil color OC contents.
• Document changes in soil properties pertinent to
  land quality.
• -Gullies
• -Stable aggregate content
• -A horizon thickness
• Pedological approach entire solum.

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Soil Map of Iowa
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Chariton Valley Overview Relative agronomic
productivity regions (CSR)
Chariton Valley --weather is too wet or too dry.
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Landscape Characteristics of the Chariton Valley
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Example landscape soils
Pershing Aquollic Hapludalf
Armstrong Aquollic Hapludalf
loess
Gara Mollic Hapludalf
paleosol
Olmitz Cumulic Hapludoll
alluvium
till Pre-Ill. (gt500,0000 years BP)
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Soil Association Map
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Field set up RCB having five clusters with 6
fields/cluster
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Within field protocol
Transects of 5 cm diameter by 1.2 m long soil
cores SWG10, SWG6, SWG3, row crops, pastures,
woodlots
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Transect
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Results OC contents
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Results Ranking of 1-m OC contents
Upland transects corrected for field
quality PasturesgtSWG10gtSWG6gtSWG3gtRow Crop w/
woodlots having the same as SWG10 SWG6
Consistently see top 20 cm has about 50 total OC
content and top 50 cm has about 80 total OC
content.
Alluvial transects Need more work because of OC
at depth.
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Results OC contents to 1-m by land use and
landscape position
General Trend FS TS gt Su Sh gt BS
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Caveat Buried OC on FS TS.
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Soil color OC
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Soil properties pertinent to land quality --
Gullies
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Summary of gullies in switchgrass fields
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Gullies in established switchgrass

• About ½ fields have gullies.
• No correlation between stand quality gully
  presence.
• Preliminary calculations suggest 250 m3 total
  volume soil lost in gullies.
• Suggests less than 1 Mg ha-1 yr-1 lost due to
  gullies.
• Problems rill sheet, dissection, off-farm

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Stable Aggregate content
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A horizon thickness (depth mollic colors)
Upland Trend Pastures gt SWG10gtSWG6 ?
SWG3 ?Row Crop ?Woodlots
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Summary

• OC ranges from 5 to 34 kg m-3 with upland land
  use ranks PasturesgtSWGgtRow Crop.
• Upland OC ratios are 0.5-0.8-1.0 for
  20cm-50cm-100cm, respectively.
• Least OC is on BS.
• Alluvial settings most highly variable.
• Soil color excellent predictor OC.
• Gullies common big problem
• SWG promotes stable aggregates thickening of A
  horizon.

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Questions Comments?
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