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Don't Let Nutrients Runoff This Winter

Livestock manure and bedding are applied to a snow-covered field.USDA’s Natural Resources Conservation Service (NRCS) is reminding Iowa farmers to refrain from surface applying manure and fertilizer to frozen, snow-covered or saturated soils.

Eric Hurley, nutrient management specialist for NRCS in Des Moines, says applying manure to snow-covered or frozen soil can easily wash away during a rapid snowmelt or during early spring rains. “Manure is too valuable of a resource and fertilizer is too expensive to risk runoff,” he said. “Not to mention the environmental impacts it would cause.”

Hurley says potash is not considered a water pollutant, but since it is such an expensive fertilizer to apply, winter application may be a risky investment that could be lost through runoff.

Iowa NRCS released its updated Nutrient Management Standard in 2013, which included new language for manure application during cold weather months. Hurley says the new standard more clearly states that manure and fertilizer storage, and management systems, should avoid surface applying nutrients when the risk of runoff his high – when soils are frozen and/or snow-covered, or when the top two inches of the soil are saturated.

“The new standard also added fertilizer to this section of the standard, which only included manure nutrients before,” said Hurley. Municipal and industrial bio-solids are also subject to the same winter management considerations as manure.

For liquid swine manure or wastewater – in which most of the nitrogen is readily available – farmers should apply the manure as close to when crops need it as possible. “This generally means a spring application during a corn year in the rotation,” says Hurley.

For manures that release nitrogen more slowly – such as solid beef and dairy manures, manure mixed with bedding, or feedlot scrapings – fall application can be more desirable since it takes time for the nutrients to be released. “In the case of surface application, there is also less risk of phosphorus runoff,” said Hurley.

Manure may be surface applied to snow-covered or frozen ground on an emergency basis if storage capacity becomes insufficient due to a natural disaster, unusual weather conditions, equipment or structural failure, or other situation that creates a risk of an uncontrolled manure release.

Hurley says if a farmer has or anticipates an emergency situation, they should contact their local NRCS office to prepare a manure disposal plan.

Manure provides many benefits to the soil as it is incorporated, especially as a valuable source of plant nutrients. It also helps build soil structure and resistance to compaction. When manure becomes part of the soil, it reduces runoff and erosion by helping to increase the soil’s water infiltration and water holding capacity.

Livestock operations subject to Iowa Department of Natural Resources (DNR) rules have different application specifications. Contact your local Iowa DNR field office for details.

NRCS field office staff is available Monday through Friday to answer questions about nutrient management, or visit the Iowa NRCS website at www.ia.nrcs.usda.gov.

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