Watershed Leaders Network

Rock Creek Farmer-Led Council

Northeast Iowa | Upper Cedar River Watershed

Iowa Soybean Association Advances Nutrient Reduction in the Rock Creek Watershed

Bioreactor installation (left) and Saturated Buffer installation (right) near Rock Creek

Iowa Soybean Association received a Water Quality Initiative Grant to improve water quality and reduce nutrient loss in the Rock Creek Watershed. The project will deliver installation assistance for edge-of-field practices – bioreactors and saturated buffers. Once the project is complete, Rock Creek Watershed will have the largest concentration of these practices in Iowa. Project partners include Mitchell Soil & Water Conservation District, Mitchell County Conservation Board, and Iowa Agriculture Water Alliance.

In a saturated buffer, a water level control structure diverts water from the edge-of-field tile main to perforated subsurface pipes that run parallel to the stream. Denitrification and uptake by perennial plants minimize nutrient loss.

A bioreactor is a trench filled with a carbon source (commonly wood chips) through which tile water flows. Microorganisms colonize on the wood chips, break down nitrate in the water, and expel nitrate as dinitrogen gas (N2), a primary atmospheric component.

Rock Creek Watershed: first Watershed Plan in Iowa to Address Nutrient Reduction Strategy

Rock Creek drains 44,787 acres of prime farmland in northern Iowa (photo credit: Lynn Betts)

In 2013, Iowa Soybean Association received a grant from the Walton Family Foundation to develop a watershed plan for Rock Creek. The plan was the first in Iowa to address Nutrient Reduction Strategy goals. Mitchell Soil and Water Conservation District received a grant for the Rock Creek Watershed through the State of Iowa’s Water Protection Fund (WPF) and Watershed Protection Fund (WSPF). Rock Creek Watershed drains 44,787 acres beginning in Worth County, continuing through Mitchell County and draining to the Cedar River in northern Floyd County.

The goals of the watershed are:

  • Reduce in-stream nitrogen by 41%
  • Reduce in-stream phosphorus by 29%
  • Increase soil organic matter by 1%
  • Maintain or increase agricultural productivity and revenues
  • Reduce flood risk
  • Maintain or increase upland wildlife habitats
  • Maintain or improve aquatic life


Practices cost-shared by the project include:

  • Cover Crops
  • Residue Management
  • Nitrification Inhibitor
  • Wetlands
  • Grade Stabilizations
  • Streambank Stabilizations
  • Waterways
  • Ag Waste Structures


Project Partners include:
Watershed farmers and landowners, Mitchell Soil & Water Conservation District, Mitchell County Conservation Board, Natural Resources Conservation Service, Iowa Department of Agriculture and Land Stewardship, Iowa Department of Natural Resources, National Fish and Wildlife Foundation, Fishers and Farmers Partnership, Iowa Flood Center, AgSolver, Inc. and Pheasants Forever.

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