St. Paul, Minn. – As winter gives way to spring, rapid snow melt and the potential for flooding pose challenges for farmers who spread livestock manure on cropland. Farmers who spread solid manure during winter must ensure that it doesn’t run off the field, with snowmelt flowing to ditches, streams and other waters.
According to the Minnesota Pollution Control Agency (MPCA), manure-contaminated runoff not only threatens water quality, it reduces the value of manure as a crop nutrient. If possible, farmers should refrain from spreading manure during periods of rapid melt. Minnesota rules to protect water quality require a 300-foot setback from surface waters and open tile intakes for all manure spread onto frozen or snow-covered soil.
If temporary stockpiling is not possible and manure land application can’t wait, to help reduce the impact of manure applied to the surface of wet, frozen or snow covered soil, choose the flattest field or flattest parts of fields and follow these guidelines:
- Field slope should be less than 6 percent for solid manure, and 2 percent for liquid manure,
- Do not apply non-incorporated manure within 300 feet of surface waters. If possible apply manure at even greater setback distances.
- Do not apply in portions of fields that contain other areas of concentrated flow. A 300-foot setback is required for intermittent streams; however most fields also contain other areas such as grass waterways that receive concentrated flow. Keep back as far as possible from these other areas of concentrated flow.
- Choose fields that contain the most crop residue; greater than 30 percent is recommended.
- Avoid fields where the furrows are full of ice and snow.
- Keep application rates low enough to avoid runoff or ponding during application.
- Choose fields that do not have adjacent non-tillable land containing areas of concentrated flow such as ravines, ditches with open side inlets, streams or dry runs. If this not possible, stay as far away as possible, from these off-field areas of concentrated flow.
When applying manure on snow-covered or frozen soils, producers should avoid high-risk periods of runoff. These include times when there are two or more inches of snow on the ground and maximum temperatures are forecast to exceed 40 degrees within 24 hours, or when there is a prediction of ¼” or more of rain within 24 hours.
“Producers should consider short-term stockpiling of manure in the field until after the major snowmelt of the year,” says Wayne Cords, a supervisor with the MPCA's feedlot program. “While this does involve additional time and labor, there are significant benefits in the reduced pollution potential, as one well-placed short-term stockpile poses significantly less pollution hazard than a whole field of surface-applied manure.”
“Producers who are considering surface-applying manure to snow-covered or frozen soils should work with a crop consultant and complete a Minnesota Phosphorus Index model to determine the phosphorus loss risk, and then choose fields with the lowest risk value to winter-apply,” Cords says. “And NPDES-permitted sites need to carefully read their permit as they have additional requirements and restrictions when applying manure to frozen or snow covered soils.”
Livestock farms that experience manure runoff into waters of the state must report to the Minnesota Duty Officer by calling 800-422-0798, and take immediate action to reduce environmental impact, such as creating temporary berms to stop discharge, temporarily plugging culverts and drain tile intakes to prevent manure inflow, and soaking up liquid with absorbent material, such as hay, straw, cornstalks or wood shavings.
For more information, see the MPCA fact sheet, “Managing manure and land application during adverse weather conditions,” contact your county or MPCA feedlot staff (see http://www.pca.state.mn.us/zihy6a1), or call the MPCA at 800-657-3864.