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Processes Controlling the Source, Movement, and Release of Soil Phosphorus in Midwestern Streams from Pasture and Crop Land

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Processes Controlling the Source, Movement, and Release of Soil Phosphorus in Midwestern Streams from Pasture and Crop Land

  1. 1. College of Agriculture and Life Sciences Processes Controlling the Source, Movement, and Release of Soil Phosphorus in Midwestern Streams Richard Schultz, Thomas Isenhart, and Michael Thompson Iowa State University Mark Tomer and John Kovar USDA – National Laboratory for Agriculture and Environment Keith Schilling IIHR - Iowa Geological Survey USDA-AFRI Foundational Program
  2. 2. Iowa Nutrient Reduction Strategy • Stream banks are known to be a potentially large source of stream sediment. • However, accurately accounting for stream bank sources of P is extremely difficult. • Therefore, evaluating strategies to reduce P losses from eroding stream banks are beyond the scope of this effort. Phosphorus Transport in Iowa Streams: The Importance of Stream Bed and Bank Erosion
  3. 3. Altered hydrology Tile drainage Channelization
  4. 4. Severely & Very Severely Erosive Banks (USDA-NRCS, 1998)
  5. 5. College of Agriculture and Life Sciences Percent Total Channel Length Classified as Erosive, by Year
  6. 6. Channel Cross-Sectional Area
  7. 7. College of Agriculture and Life Sciences Distance (m) 0 2 4 6 8 10 12 Elevation(m) -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 2014 1998 1998 2014 Change in Cross-Sectional Area, 1998-2014
  8. 8. Change in Cross-Sectional Area, 1998-2014 Distance downstream (km) 0 2 4 6 8 10 12 14 Percentchange -20 0 20 40 60 80 Increase Decrease
  9. 9. Recession Rates Full Set Biannually Focus Set Monthly, or by Flow Event
  10. 10. Robert’s Creek Member 3500 – 500 YBP Gunder Member 10,500 – 4500 YBP Camp Creek Member 400 YBP - Present Slump Material
  11. 11. College of Agriculture and Life Sciences
  12. 12. Recession Estimation with LiDAR
  13. 13. Assessing In-Channel Sediment Storage Bankfull
  14. 14. College of Agriculture and Life Sciences In-Channel Sediment Storage by Feature
  15. 15. Event Sampling at Guage Stations
  16. 16. Silt Loams, Coarser with Depth
  17. 17. Camp Creek Roberts Creek Gunder Till Photo courtesy of John L Kovar Sediments pH OM Sand Silt Clay Fe-CBD Fe-ox Ca-M3 ---------------- % --------------- -------------mg/kg----------- Camp Creek 6.2 3.4 11 63 25 6,825 3,348 1,975 Roberts Creek 6.3 4.5 13 60 27 5,682 3,947 2,983 Gunder 7.4 1.5 6 72 22 3,813 1,967 2,135 Till 8.1 1.7 49 31 21 10,124 743 6,750 Stream Bank Soil Characteristics
  18. 18. College of Agriculture and Life Sciences Sequential Phosphorus Extraction
  19. 19. Soils Sampled for P Adsorption-Desorption Studies
  20. 20. Upland restoration, yet no trends in sediment load, eroding streambank length, streambank recession rate
  21. 21. Observed Processes
  22. 22. College of Agriculture and Life Sciences Simon and Hupp, 1986, Simon and Rinaldi, 2006
  23. 23. College of Agriculture and Life Sciences Tentative Conclusions Entire study reach within Stage IV Simon and Hupp, 1986, Simon and Rinaldi, 2006 Slow transition from initial 20th century disturbance Simon and Rinaldi, 2000 (could take 40-100+ years) Cohesive Gunder bed and banks
  24. 24. College of Agriculture and Life Sciences Distance downstream (km) 0 2 4 6 8 10 12 m3 m-1 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 Channelized Meandering Total In-Channel Sediment Storage
  25. 25. College of Agriculture and Life Sciences N ovem ber2014M arch 2015April2015M ay 2015June 2015July 2015 August2015 Septem ber2015 O ctober2015 Volume(m3) 0 200 400 600 800 1000 1200 1400 1600 1800 Walnut Creek Cumulative Streambank ErosionCumulative Streambank Erosion Volume(m3)
  26. 26. College of Agriculture and Life Sciences Image adapted from Schilling et al., 2012 Walnut Creek Watershed • Perennial, third order stream • 5218 ha • Agricultural headwaters, subsurface drainage • Extensive channelization • Water Quality Data 1995 – • Neal Smith NWR (2225 ha) • 1991 - Present
  27. 27. College of Agriculture and Life Sciences Distance (m) 0 2 4 6 8 10 12 Elevation(m) -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 2014 1998 1998 2014 Change in Cross-Sectional Area, 1998-2014

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