Edge of Field Resources | Building a Culture of Conservation

Edge of Field Resources

Edge-of-field practices play a crucial role in meeting the Iowa Nutrient Reduction Strategy goals of improving water quality through reducing nitrogen and phosphorus in Iowa's water bodies. Edge-of-field practices involve bioreactors, buffers, saturated buffers, denitrifying wetlands, terraces and sediment control.

Ten Ways to Reduce Nitrogen Loads from Drained Cropland in the Midwest - publication by Illinois Drainage Research and Outreach Program that highlights practices designed to reduce nitrogen loads from cropland. 

Bioreactor installationBioreactors

Tile-drained water is routed to woodchip filled trench located in a grassed buffer where the tile drainage leaves the field.  Once the water enters the bioreactor, denitrification begins.  Bacteria use the carbon from the woodchips as a food source and the incoming nitrate for their respiration process.  Bioreactors can reduce nitrate levels by 15-60% in tile-drained water.

Talking With Your Tenant - Denitrifying Practices
Bioreactor Research by Iowa State Agriculture Water Management Team
Woodchip Bioreactors for Nitrate in Agricultural Drainage
Applying Woodchip Bioreactors for Improved Water Quality Infographic


Wetlands are characterized as having water at or near the soil surface during at least part of the year, containing hydric soils, and containing plants that are adapted to wet conditions.  These characteristics provide a great environment for denitrification. Wetlands are shallow in depth and allow the water to slow down and deposit sediment. On average, wetlands can remove 40-90% of nitrates. 

Talking With Your Tenant - Denitrifying Practices
It Begins with You - Wetlands Implementation
Wetlands Implementation Infographic 
Iowa Conservation Reserve Enhancement Program (CREP)
Agricultural Pesticide Impacts on Prairie Wetlands
Iowa Watershed Approach Wetlands Infographic


saturated buffer illustrationSaturated Buffers

Tile drainage water is directed into lateral drainage tile installed parallel to a riparian buffer.  The water moves across the length of the buffer removing nitrate.  The microbes living in the saturated zone use the nitrate in the water as part of their respiration process. Plants in the buffer also remove nitrates from the drainage water through root uptake. Saturated buffers can remove, on average, 50% of the nitrates in subsurface flow.


Talking With Your Tenant - Denitrifying Practices
Cleaning Iowa's Waters with Saturated Buffers
Saturated Buffer Strips: Drain, Sustain, & Gain
Questions and Answers about Saturated Buffers for the Midwest




Farm ponds, grade stabilization structures, oxbow restoration, buffers, terraces and sediment control structures are designed to settle sediment and sediment-bound N and P, along with retaining nitrate-N and dissolved P. These practices also provide wildlife habitat, sequester carbon, reduce greenhouse gas emissions, stabilize stream banks, and potentially reduce flood impacts. terraces

Water Quality and Conservation Practices
Conservation Buffers and Water Quality
Vegetative Filter Strips - For Improved Surface Water Quality
Small Changes, Big Impacts: Prairie Conservation Strips
A Landowner’s Guide to Prairie Conservation Strips
The Cost of Prairie Conservation Strips
Assessing the Need for a Riparian Management System
Maintenance of Riparian Buffers
Buffer Strip Design, Establishment, and Maintenance
Farm Ponds - Iowa Watershed Approach
Sediment Control Basins - Iowa Watershed Approach
Grade Stabilization Structures - Iowa Watershed Approach
Oxbow Restoration - Iowa Watershed Approach


NRCS ag water drainage control structureDrainage Water Management

Drainage water management is the practice of using a water control structure in a main, submain, or lateral drain to vary the depth of the drainage outlet. The water table must rise above the outlet depth for drainage to occur.

Drainage Water Management for the Midwest