June 27, 2008

Although not especially glamorous or flashy, grassed waterways should be part of an erosion control plan on nearly every farm. Unfortunately, as farm equipment has gotten larger and more land is farmed by one operator, grassed waterways have tended to go out of favor.

Designing Waterways

Grassed waterways are broad, shallow, shaped channels designed to carry surface water across farmland without causing soil erosion. The vegetative cover and root system in the waterway slows the runoff water flow and protects the channel from erosion. Waterways are constructed in natural depressions where the water collects and flows to an outlet. When properly sized, constructed, and maintained, grassed waterways will safely convey water down slopes.

The recent rains have made it quite obvious where grassed waterways should be located in many Nebraska fields, especially those that were not planted using a no-till system. Look for areas where eroded channels have formed along the natural flow paths. These meandering channels are typically six inches or more in depth and a foot or more wide. The newly emerged crop that was planted in the area where the channel developed has been washed out, and plants on both sides of the channel appear damaged from the water that flowed over them. Soil that was eroded by the flowing water has been carried downstream, as has any applied fertilizer and/or pesticide. All of these contribute to water quality degradation. Installing a grassed waterway is one solution to this problem.

Disadvantages and Advantages

Granted, installing a grassed waterway has some drawbacks. Land must be removed from crop production. Equipment must be raised or sprayers shut off when crossing. Some maintenance is needed periodically so that gullies don't form along the edges. Incidental grazing is generally not allowed if the waterway was installed under a tax-funded conservation program.

However, there are many positive aspects to installing a grassed waterway. Annual payments for land rental and maintenance costs are available to help offset the lost crop production. Fuel, labor, and other costs associated with tillage to periodically fill in the eroded channel are eliminated. Equipment damage from crossing the eroded channel is eliminated. Wildlife habitat is improved. Water quality is enhanced.

Take a moment to close your eyes and visualize two different scenes. First, think of a newly emerged corn or soybean field during a typical spring thundershower. Visualize the water running down the rows and gathering into the low areas, washing out the young plants, carrying away the topsoil, and forming an eroded channel through the field. See the dark, muddy flow of water winding its way down the slope.

Now visualize that same field but with a thick stand of grass in flow areas that have been graded and reshaped. See how the runoff water is quite clear and is slowed and directed safely down the slope.

Which scene is typical on your farm?

Visit the local Natural Resources Conservation Service Field Office to discuss where grassed waterways and other conservation practices can be installed on your farm. Do your part to help reduce erosion and protect water quality.

David Shelton
Extension Agricultural Engineer
Haskell Agricultural Laboratory, Concord