What is in this article?:
- Escaped Sediment Being Blamed on You | Conservation Practices have Slashed the Amount of Soil Moving from Farm Fields into Waterways
- Q & A: Understanding farm-field erosion and sediment loss
- How well are farmers controlling soil erosion from their fields today?
- How does tile drainage affect soil erosion?
- Does tile drainage increase stream-flow volumes?
- How to reduce sediment loss
- The right thing to do
- Drainage innovations help protect water quality
How to reduce sediment loss
Farmers have made real gains in reducing cropland erosion and sediment loss, says Iowa State University Extension Agricultural Engineer Matt Helmers. “But there’s a lot more we can do.”
Start with residue and tillage management. “Residue is the single most important factor influencing soil loss,” says Jodi DeJong-Hughes, a University of Minnesota Extension tillage expert. Residue protects the soil from raindrop impact, slows down water velocity over the field, decreases soil detachment and soil sealing and increases water infiltration.
“All tillage decreases residue cover,” Helmers says. “Think about how you can increase residue and reduce tillage.” Iowa Learning Farms Project modeling shows that reduced-tillage systems cut soil loss by up to 90% in erodible fields, he adds.
Stop disking ephemeral gullies. “We have to stop doing that!” says Minnesota NRCS State Conservationist Don Baloun.
Rainstorms carve out these small ditches in fields, which then transport field runoff laden with sediment. Tillage can temporarily hide them, but they usually reappear and can lead to significant sediment loss, Baloun says.
In areas prone to ephemeral gullies, he says, farmers must reduce tillage to keep soil covered and establish grass waterways or strips to slow water flow.
Install a buffer. These grassy strips between fields and water bodies filter out sediments and nutrients from surface runoff and shallow groundwater. A correctly designed and placed buffer can trap 90% of sediment from the drainage area, Helmers says. “In the future we may consider designing buffers that vary in width, according to water-flow patterns at the site.”
Protect tile outlets. Water coming out of drainage pipes has energy and can contribute to ditch or stream-bank erosion, says Gary Sands, a University of Minnesota Extension biosystems engineer. There are many ways to protect tile outlets. “Often, it’s just a simple matter of placing some rocks or ‘rip-rap’ at the outlet.”
Fix eroded side inlets. “This is another area that needs more attention,” Sands says. Eroded ditch inlets widen and deepen over time. There are many good, inexpensive ways to stabilize them, he says.
Improve open surface tile intakes. Runoff entering old-style open tile intakes carries sediment, phosphorus, and other pollutants through the drainage system and into surface waters, Sands says.
Alternative intakes such as rock or blind intakes and slotted intake risers, like the familiar orange Hickenbottom risers, are good options, Sands says. These practices allow more sediment to settle out in the field, before going down the drain. Farmers don’t much like working around intake structures, he acknowledges, but they are “a tremendous improvement over open intakes.”
Add a perennial to your rotation. “These are very effective” at controlling erosion, Helmers says.