Need to spread on a high-risk day?

Today’s Runoff Risk Advisory Forecast isn’t just determined by today’s weather and soil conditions. The forecast for today is looking ahead to the next 3 days to see if runoff triggering events are going to occur. Why? Because manure applied today could easily runoff with tomorrow’s rains!

Therefore, avoiding spreading manure/fertilizers on days of highest risk is always the safest option to help avoid potential runoff issues. However, this is not always possible given the wide variety of farming operations and management across the state. Use the following advice on high-risk days:

  1. Assess the risk for each field before a fertilizer/manure application

    The RRAF maps are based on a National Weather Service flood forecasting model. Cropped fields are typically much smaller than the 2km x 2km (approx. 1.25 x 1.25 sq. mi.) grids used in the model and can vary considerably within each grid. Local landscape/terrain characteristics can significantly affect the model’s applicability to a specific field. Always apply your own knowledge of the landscape and current field conditions when assessing the risk of runoff for your fields. Things to consider include:
    • Risk increases as soil moisture increases
      The model considers area-wide average conditions for soil moisture. If you know that your fields are particularly wet (for example, you experienced a recent rainfall event that was greater than other areas nearby) you should know that the risk of runoff from your fields will be higher than what is shown on the risk map.
    • Even if the map shows low runoff risk, your fields may not be dry enough to spread
      Applying liquid manure to wet fields can lead to direct manure runoff, even if the field is otherwise a low risk site. Make sure your fields are dry enough to accept additional moisture. If liquid manure should runoff or pond in a field or discharge into tile lines, application must be stopped until the runoff can be contained.
    • Liquid manure applications increase soil moisture
      An application of 27,000 gallons per acre of liquid manure is the equivalent of adding approximately 1 inch of water to your fields. A liquid manure application effectively increases your soil moisture, and therefore the risk of runoff from fields receiving liquid manure will be higher than what is shown on the risk map.
    • Snow-covered and frozen fields are high risk
      The model considers area-wide average conditions for snow cover. If you have snow in your fields but the map does not show winter conditions, you should know that the risk of runoff from your fields will be higher than what is shown on the risk map. The opposite may hold true if the model shows snow across the area, but there is none in your fields.
    • Some fields are always higher risk
      These are areas of concern on your farm and might include fields with higher slopes, tighter soils, poor drainage, or fields close to sensitive features such as ponds, streams, lakes, wetlands, sinkholes, etc. You should always use caution and follow all appropriate setback distances when applying manure or any agrichemical products in these areas, regardless of what the risk map indicates.
  2. If you must haul manure during high runoff risk times:

    Avoid field spreading manure by:
  3. If field spreading of manure is necessary:

    Identify lower risk fields for spreading or stacking manure
    • Apply to your driest fields
    • Use the SnapMaps 590 and NR 243 Restriction Maps ( in your Nutrient Management or Conservation Plan to find fields with:
      • Low slope
      • Low erosion, and
      • Low delivery potential
    • Apply to flatter fields without channelized flow or gullies
    • Apply to fields farthest from surface water
    • Avoid fields with conduits to groundwater
    • Avoid fields with areas of concentrated flow
    • Follow all other nutrient application restriction guidelines detailed in the NRCS Field Office Technical Guide standard 590, Nutrient Management.