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Now is high-risk time for manure runoff


February 10, 2011
By University of Wisconsin Discovery Farms

manuresnowNEWS HIGHLIGHT

Now is high-risk time
for manure runoff

Livestock producers who apply manure to agricultural fields need to be
aware that spreading manure from now until the ground thaws has an extremely
high risk of runoff.

February 8, 2011, Madison,
WI – Livestock producers who apply manure to agricultural fields need to be
aware that spreading manure from now until the ground thaws has an extremely
high risk of runoff.

Studies from farms
cooperating in the Discovery Farm Program indicate that manure applied to snow
covered and/or frozen soils during conditions of snow melt or rain on frozen
soils can contribute the majority of the annual nutrient losses.   

manuresnow  

 

Forecasted air
temperatures are predicted to become milder starting the week of February 13
throughout much of Wisconsin, with daytime highs expected to occasionally climb
into the 40s. Daily high temperatures are predicted to be above freezing for at
least a week in southern Wisconsin. This relatively prolonged period of warmth
is expected to be accompanied with chances for rain. The combination of warm
air temperatures and increasingly stronger sunshine could lead to snow ripening
and starting to melt next week. Rainfall additions could contribute to
additional snowmelt and increase the potential for surface runoff from farm
fields.

Snowmelt runoff has the
potential to be big this year. Snow depths are generally one to two feet throughout
much of Wisconsin, which is much higher than normal, especially in Southern
Wisconsin. In Madison, for example, there is typically about five inches of
snow on the ground in early February. As of February 3, there was nearly 20
inches. If all of this snow were melted, the liquid equivalent would be
approximately two to four inches, with as much as 6 inches or more in some
areas of the state.

Frost depths are generally
ranging from eight inches to more than two feet. Although the snow is deep –
which tends to insulate soil and limit frost depth – the brief warm up near the
end of December reduced the snow pack and allowed the cold air to penetrate
deeper into the soil. The brief warm-up also consolidated some of the heavy
December snows, and in many places there are icy layers within the snow pack
and on top of the soils. In addition to frozen soils, these ice layers may
further reduce infiltration and increase the potential for surface runoff.

As the temperatures
moderate producers need to listen to the weather forecast. Avoid spreading
manure when there is a high probability of rain on frozen soils. What can
producers do to reduce the risk of manure run off?

  • During the period of
    active snow melt or when rain is predicted on frozen soils, producers who must
    haul manure from their barns should stack it in an area where the potential for
    runoff or groundwater infiltration is low,
  • Farmers who daily haul
    manure should work with their local conservation departments to identify safe
    stacking sites that have minimal potential to runoff into either surface or
    groundwater,
  • Producers who have lots or
    facilities with bedded pack systems need to be cautious about spreading this
    manure during this high risk period. 
    Cleaning lots and getting the manure on the fields before the frost goes
    out can greatly increase the potential for nutrients losses,
  • Producers who must haul
    manure during this high-risk period should identify fields that are away from
    streams or lakes and have minimal risk of manure running to surface or
    groundwater.

 We are saying that there
is a high potential for manure runoff this year based on the current field
conditions and typical weather patterns. This doesn’t mean it will happen. If
temperatures rise slowly, cloudy days or the lack of rain can greatly reduce
the chance of runoff. Producers need to listen to the weather forecast and make
good management decisions. Good decisions can reduce the risk of runoff events
and continue to protect our farms and our water.


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