Land application is the most common method of animal waste management in Wisconsin. A significant risk of land spreading manure is its entry into streams, lakes and groundwater. Oxygen demanding organic matter, bacteria, pathogens and nutrients from manure can be transported into surface and groundwater posing significant public health and environmental risks. The most common and readily apparent transport pathway for surface-applied liquid manure into surface waters is via surface runoff. To reduce odors and runoff risk and to capture maximum fertilizer value, many producers inject liquid manure directly into field soils. For nontiled fields surface application and injection are appropriate methods of manure application when soil conditions (moisture, slope, frost, etc.) are right and when done at application rates appropriate for soil assimilation. The existence of tile drains may, however, render surface application and injection inappropriate by providing direct transport pathways for liquid manure to surface waters. Manure can enter tile drains via surface inlets, open cavities created by tile blow-outs and via soil macro-pores (earthworm holes, soil structural cracks and former root channels).
Soil Science Extension
University of Wisconsin Madison