Effects of Winter Manure Application in Ohio On the Quality of Surface Runoff.

Six continuous corn, instrumented watersheds (approximately 1 ha each) at the USDA-ARS North Appalachian Experimental Watershed research station near Coshocton, Ohio were used to evaluate environmental impacts of applying manure to frozen soil.  For 3 years on frozen, sometimes snow-covered, ground in January or February, two watersheds received turkey litter; two watersheds received liquid swine manure; and two watersheds were controls (received N fertilizer at planting, not manure).  Manure was applied at an N rate for corn; the target level was 180 kg N ha^-1.  There was a 33m setback from the area of application to the bottom of each watershed.  In addition, four grassed plots (61 x 12m) were used for beef slurry applications (9.1 Mg ha^-1 wet weight); 2 plots had 61 x 12m grassed filter areas below them; 2 plots had 31 x 12m filter areas.  There were 2 control plots, one for each of the 2 filter sizes.  Ohio NRCS recommends a 61m buffer area for winter manure applications along with slope and vegetative cover recommendations.  “Dustpan” runoff samplers were placed at the lower edge of each plot application area and 11m downslope; runoff was collected at the base of each filter area.  Although nutrient and pathogen (E. coli and enterococci) concentrations in runoff were measured, only nutrient results are reported here.  Nutrient concentrations can be high, especially in runoff soon after application.  However, most events with high concentrations occurred with low flow volumes, and therefore transport was minimal.  There were greater potential detrimental environmental impacts with P than with N.  Filter strips reduced nutrient concentrations and transport, but the data were too limited to compare the effectiveness of the 31m and 61m filter strips.  Winter application of manure is not ideal, but by following prescribed guidelines, detrimental environmental impacts can be reduced.