What happened to our grassed waterways?
By LuAnn Rolling, District Conservationist
Driving around Allamakee County today I am shocked by the lack of grassed waterways and the number of undersized waterways that have gullies running down both sides. We are experiencing more higher volume, higher velocity rainfalls than we have ever had in the past.
This should prompt the installation of more and bigger waterways, not the removal.
When USDA conducts random 5% spot checks of conservation plans, one of the easiest ways to tell if a producer is not following the plan is seeing gullies in the field. This is usually obvious when water runs off a field and leaves a gully where grass should be. To best transport water, the grassed waterway should be “parabolic” or bowl shaped so water stays in the grassed area.
If there is grass in the waterway there should NEVER be crop rows that run adjacent (up and down with the waterway). How would water ever get to the grass in this scenario? Obviously, the adjacent rows will carry the water and create gullies and not allow the waterway to function like it should.
Other ways to improve waterway function and longevity would be to do no-till and plant cover crops. In addition to controlling erosion over time these practices will increase water infiltration leaving less water to exit through the waterway.
If a waterway is functioning properly, it will eventually require maintenance. Necessary operation and maintenance items include:
1. Inspect regularly and after significant storm events. Fill, compact, and reseed any damaged areas immediately.
2. Remove sediment deposits to maintain the capacity of the waterway.
3. Minimize damage to vegetation by excluding livestock whenever possible, especially during wet periods.
4. Promptly repair vegetation damaged by farm equipment, herbicides, livestock, or erosion.
5. Avoid using herbicides that would be harmful to the vegetation or pollinating insects in and adjacent to the waterway.
6. Avoid using the waterway as turn rows during tillage and cultivation operations.
7. Avoid tillage and planting operations parallel to the grassed waterway. Parallel operations may divert runoff water from the grassed waterway and lead to the formation of gullies adjacent to the waterway.
There is cost sharing available to install grassed waterways through the Allamakee Soil and Water Conservation District. It is 50% of the cost to shape and seed the waterway and includes fabric checks for spring construction and mulch blanket for fall construction.
Some argue that NRCS waterway designs are bigger than necessary for their issue. But bouncing through gullies and damaging equipment can easily amount to more lost dollars in repair costs than the few extra acres that may be required to meet an NRCS properly designed waterway. A small gully, 1’ wide by 6” deep by 300’ long, equals 6 tons of soil lost. It is not uncommon to see several of these gullies in a field, and they are occurring every year.
A recent study conducted at Ohio State University by Soil Scientist Rattan Lal found that topsoil erosion vastly reduces crop yields. Fifteen years of studying erosion and yields showed corn yield on the eroded-topsoil plot fell by about half, 51%, compared to the control plot.
Dr. Rick Cruse, a professor of agronomy and director of the Iowa Water Center at Iowa State University, recently said that our soil - which naturally regenerates itself at the rate of 0.5 tons per acre per year - is currently being lost at more than 11 times that rate. This translates into 1 pound of soil lost for every pound of corn produced in the state. Cruse adds that the loss of soil through erosion and the contamination of surface and groundwater are surely two of the biggest issues of concern to all Iowans.
If you have gullies in your field, or if you are having difficulty maintaining your grassed waterways, visit the NRCS office today for assistance.
