Setbacks: According to the GAAMPs, manure should not be applied within 150 feet of any surface water unless incorporated within 48 hours of application, which is not practical on frozen, snow covered fields. Catch basins, grass waterways and any area water collects and flows toward surface water are also high risk areas. Maintain the 150 foot setback from those areas as well. Preferably the setback should be growing established vegetation or covered with undisturbed crop residue.
Weather forecast: Research has shown that nutrient loss increases if manure is winter applied 5 to 7 days prior to a runoff event. Monitor weather forecasts and avoid manure applications if a warm up in temperature or rain is predicted for the immediate future. Nutrient losses are reduced by a larger window of time between the application of manure to snow covered, frozen fields and a snow melt, winter runoff event.
Timing of manure application: Apply manure early in the winter. Avoid spreading in late February early March when there are greater odds of a large sudden snowmelt and/or rainfall event. Or, if manure must be spread throughout the winter, choose fields with a higher degree of risk early in the winter saving low risk fields for later in the winter and early spring.
Application rate: Follow the normal farm manure application rates based on the nutrients in the manure and the needs of the crop to be grown. Do not exceed the nitrogen (N) needs of the intended crop.
There are legitimate reasons for winter manure application. From delayed field work in the fall resulting in farmers needing to empty manure storages in the winter to farms with bedded housing and depending on daily hauling, there will be times when manure must be applied in winter months. Livestock farmers should recognize the associated environmental risks with winter spreading. Individually evaluating each field and utilizing the practices listed above helps reduce those risks.