Agricultural nutrient management continues to be an important area of research and policy due to concerns of phosphorus (P) loss in runoff and water quality degradation. Surface manure application to fields without incorporation can be a significant source of P loss (Daniel et al., 1998). In many northern states, winter manure application without incorporation is common (Srinivasan et al., 2006). This fact, combined with frequent snowmelt runoff, has prompted some states to restrict winter manure spreading. However, restrictions are based more on commonly held perceptions than on research. Studies of winter manure P loss are limited, and most have been observational with mixed results (Kongoli and Bland, 2002). P transport from winter‐applied manure varies due to infiltration, runoff, erosion, and nutrient cycling processes, all of which are sensitive to air and soil temperatures. Manure P loss also varies with spreading practices, especially relative to manure placement beneath or on top of snow and the effect of manure on rates of snow melt (Williams et al., 2011). Overall, good understanding of P cycling and transport associated with winter manure application is still lacking.
Soil Science Extension
University of Wisconsin Madison