Iowa Nutrient Reduction Strategy

Safeguarding Iowa’s Water and Soil

Safeguarding Iowa’s water while improving the health of our soil is important to the well-being of Iowa agriculture. To that end, Iowa has set aggressive goals in reducing nutrient losses under the Iowa Nutrient Reduction Strategy (INRS). A combination of nutrient management and conservation practices will be needed to meet INRS goals, which are to reduce nitrogen and phosphorus loading into Iowa waters from non-point sources (including agriculture) by 41 and 29 percent, respectively.

INRS Nitrogen and Phosphorus Reduction Practices

Source: Data from the INRS (IDALS, IDNR, ISU CALS). Images courtesy of Iowa Soybean Association.
These charts show the effectiveness of specific practices at reducing nitrogen and phosphorus losses into lakes, rivers and streams as outlined in the INRS.

Nitrogen Load Reduction

Average nitrate-nitrogen concentration or load reduction as a percentage. Horizontal bars represent one standard deviation above and below the mean. Dashed line represents the 41% nitrogen reduction goal from nonpoint sources.

Phosphorus Load Reduction

Average phosphorus load reduction as a percentage. Horizontal bars represent one standard deviation above and below the mean. Dashed line represents the 29% phosphorus reduction goal from nonpoint sources.

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Best Management Practice to Reduce
Nitrogen Losses from Drained Cropland

  1. Improve nitrogen management using 4R nutrient stewardship practices.
  2. Plant cover crops to take up water and nutrients from the soil.
  3. Increase perennials in row crop rotations to reduce both drainage flow and nitrate loads.
  4. Use adjustable, flow-reduction structures placed in the drainage system.
  5. Reduce drainage intensity with wider-spaced tile lines and/or place them closer to the surface.
  6. Recycle drainage water by storing it in a pond or small reservoir and then returning it back to the field through the drainage tile during dry periods.
  7. Add bioreactors to channel tile water through a carbon source – usually wood chips – and denitrify the water.
  8. Incorporate wetlands to remove nitrates through denitrification, plant uptake and reduction in flow.
  9. Install a two-stage drainage ditch to retain nitrates through uptake by ditch’s vegetation and by biofiltration when tile water passes through the vegetation.
  10. Use saturated buffers to allow tile water to be redirected into the vegetative buffer and seep through the buffer’s root zone.

Sources: Christianson, L.E., J. Frankenberger, C. Hay, M.J. Helmers, and G. Sands, 2016. Ten Ways to Reduce Nitrogen Loads from Drained Cropland in the Midwest. Pub. C1400, University of Illinois Extension. Reducing Nutrient Loss: Science Shows What Works: Iowa State University Extension and Outreach. SP435. September 2017