Farm management was no-till corn or soybeans on 4-6 % slope silt loam soil with terraces and grassed waterways in place.  Livestock manure was applied at typical rates in either the fall or late winter just before snowmelt, such that both application time periods were monitored each year.    

Through the study, 50 – 100 % of surface-water runoff occurred when ground was frozen.  The remaining runoff occurred in spring when vegetative cover was minimal and soils were wet.

Suspended sediment loss ranged from 5 – 20 lbs/ac each year.  Most of total P lost was dissolved; not associated with sediment loss.

Each basin with manure applied shortly preceding snowmelt had wintertime total P losses (1.6 – 3.4 lbs/ac) three times higher than basins with fall applied manure (0.3 – 1.4 lbs/ac).

Similarly, basins with manure applied shortly preceding snowmelt had wintertime total N losses (5.0 – 7.8 lbs/ac) more than two times higher than basins with fall applied manure (0.6 – 2.8 lbs/ac).  In all cases, total N loss where manure was applied just before snowmelt was primarily in organic and ammonium forms.

Livestock manure applied to snow covered and frozen ground shortly before and during periods of surface runoff caused a substantial increase in total P and N losses from these fields. The fact that these nutrients are mostly dissolved P and organic / ammonium N suggests their origination is from the manure.  Livestock manure applications in late fall, even at higher rates, had a minimal impact on P and N loss in snowmelt runoff.