As of 2012, there were more than 143,000 animal units in Dane County. Eighty percent, or 63,000 animal units, reside in the Upper Yahara sub-watersheds located within Dane County. The high animal density in the Upper Yahara sub-watersheds leads to manure phosphorus applications that are greater than the phosphorus removed through crop uptake, leading to increased phosphorus concentrations in soils. Unfortunately, this increase in soil phosphorus concentration leads to greater edge-of-field phosphorus loss in runoff events. To reduce these losses, the amount of phosphorus applied should be balanced with phosphorus crop uptake to avoid soil phosphorus buildup. In fields where phosphorus buildup has already occurred, phosphorus applications must be less than phosphorus crop uptake to reduce soil phosphorus concentrations. Better understanding the impact of livestock manure on water quality can inform clear, long-term manure management goals for the Yahara Watershed to reduce phosphorus loading from livestock manure.

Published by University of Wisconsin-Extension and UW-Madison College of Agricultural and Life Sciences, Biological Systems Engineering