Know the Laws and Use Caution for Winter Manure Application

Like it or not, sometimes winter manure application becomes a necessity. Producers are urged to be aware of their state’s laws and rules governing winter application before heading for the field. When winter spreading is the only option, several key considerations should be taken into account.

The best nutrient utilization will come from applying manure as close to the time of crop uptake as possible, and that is not during winter, says Douglas Beegle, Penn State Extension soil fertility specialist. “In winter, when temperatures on the surface of the soil fall below 50^oF, the potential volatilization losses are less. However, there is significant potential for losses of surface-applied nutrients in runoff from snow melt or winter rains under these conditions,” he says. Beegle suggests applicators time application and select fields based on how to minimize the potential for loss.

Late-winter surface application on snow-covered, frozen soil on slopes of greater than 5% has the greatest risk of runoff, according to Charles Wortmann, University of Nebraska nutrient management specialist. Writing in the Nebraska CropWatch newsletter, he also points out the risk of loss is generally greater with winter surface application of liquid/slurry compared to solid manure. Surface application poses a greater risk than injection or incorporation, unless incorporation is on highly erodible land.

Penn State’s Beegle offered the following additional tips in a recent issue of the Penn State Field Crop News:

1. Select fields with cover crops or at least good residue. Be aware of regulations for cover crops or residue; some states require a cover crop, or at least 25% residue for winter spreading.
   
2. Stay as far away from water as practical, and take note of regulations that require specific distances for spreading near water sources in winter.
   
3. Avoid areas in fields where concentrated water flow is likely.
   
4. Avoid poorly drained fields.
   
5. Don’t spread on snow unless it is unavoidable.

Iowa producers, in particular, need to be aware that a law that went into effect Sept. 15, 2010, says confinement feeding operations that have more than 500 animal units cannot legally apply liquid manure on snow-covered ground from Dec. 21 to April 1, or on frozen ground from Feb. 1 to April 1, except in an emergency. The Iowa Manure Management Action Group (IMMAG) says frozen ground is defined as “soil that is impenetrable due to frozen soil moisture but does not include soil that is frozen to a depth of 2 in. or less.” Snow-covered ground is defined as “soil covered by 1 in. or more of snow or ½ in. or more of ice.”

Operations regulated by these Iowa rules can apply manure in an emergency, but the emergency must meet specific definitions. Producers should contact their local Department of Natural Resources (DNR) office to make sure they are following local restrictions.

View a Web cast demonstrating winter manure application and featuring Jeffery Lorimor, former Iowa State University Extension manure management specialist online at connect.extension.iastate.edu. Visit the IMMAG website at www.agronext.iastate.edu/immag/. Read the Nebraska CropWatch newsletter at cropwatch.unl.edu/web/cropwatch/. The online Penn State Field Crop News is at fcn.agronomy.psu.edu.