DES MOINES – Runoff and nutrient loss are more likely following winter manure application because manure can’t be injected into the soil or incorporated into the field.
Research shows that the later in the season and the closer to spring snowmelt that you land apply manure, the greater the risk that it will reach a stream. So, it pays to be careful when winter application is necessary, both to make the best use of the nutrients and to protect water quality.
For animal producers with totally roofed (confinement) facilities, state law also sets some dates, Dec. 21 and Feb. 1, when liquid manure cannot be applied on snow-covered or frozen ground. These limits affect confinement facilities with liquid manure that have 500 or more animal units. Generally, 500 animal units is 1,250 finishing hogs; 5,000 nursery pigs; 500 steers, immature dairy cows or other cattle; or 357 mature dairy cows.
Except in emergencies, the law limits liquid manure application from Dec. 21 to April 1 if the ground is snow-covered with an inch or more of snow or one-half inch of ice. If manure can be properly injected or incorporated, it can be land applied during this time. Starting Feb. 1, liquid manure application on frozen ground is restricted.
Producers must call the local DNR field office to report emergency applications before they apply.
While the law affects confinements with liquid manure, open feedlots and poultry producers can help keep manure in place by using common sense and choosing application areas far from a stream, on flat land with little snow cover.
All producers must follow setbacks from certain buildings and environmentally sensitive areas.
Search for more information on separation distances at www.iowadnr.gov/afo/
. Recommendations from the Iowa Manure Management Action Group about applying manure in winter are available at www.agronext.iastate.edu/immag/pubs/imms/vol3.pdf
The rules are available online under Chapter 65 of the Iowa Administrative Code/Environmental Protection Commission.