Using the ARM Weather Map
The ARM Weather Map is your first line of defense against having a runoff event. It’s primarily purpose is to identify those conditions that could lead to a runoff event. These conditions are geographical location and projected/forecasted precipitation amount.
Prior to applying manure it is recommended that you look at the ARM Weather Map for the current and three day spreading risk rating. To do this, click on your geographical location on the map. A window will pop that shows the risk rating for each of three days. Use this to choose the most appropriate day to apply manure to. This helps you plan ahead. Remember: if the risk is high, don’t apply.
If the risk is low today, but high tomorrow, consider waiting until conditions are more favorable. This would be a day that has a low risk for application followed by two days of medium or lower risk. In general, you want a few days in which the manure can be taken up by your soil. This consideration will vary throughout the year and is much more important in the high risk wet seasons when soil saturation and large rain events are possible. Both of these things can readily move nutrients, pathogens, and sediment from your field.
If the risk is low and you plan on applying manure, apply the seasonal manure setback distance to all areas adjacent to a waterbody or conduit to a waterbody.
About the Forecast
The forecast used for the ARM Weather Map comes from model precipitation prediction data by NOAA. This data is updated at least once daily.
Link to read more about how NOAA derives and assesses precipitation data: https://water.weather.gov/precip/about.php
NOAA disclaimer on use of forecast data: https://www.weather.gov/disclaimer
Field Risk Type Definition
A high risk field is one that is likely to have a runoff event and/or impact an adjacent waterbody. High risk fields are saturated (over 90% moisture = you could not drive a tractor on it, water appears under your footprint, a handful of soil would produce moisture on your hand), has a water table within 24 inches of the surface and/or flowing tiles, is frozen more than one inch down, has thin vegetation (<70% density), and/or has high risk areas. High risk areas are swales, trenches, ditches, ponded areas, or other conduits that would channel water from the field to adjacent water way. Do not apply to high risk fields! Wait for them to become more suitable before applying.
A low risk field is one that has a low chance for a runoff event. Characteristics include, well drained, sandy soil; low soil moisture; no adjacent waterways or a upslope or burm that prevents water from entering waterway; no swales that lead to a critical area; adequate vegetation cover if surface applying; and no ponding or water table within two feet of the surface. If you can drive a tractor on your field without causing mud or ruts, it is likely at a low risk state.