Water Quality from Grass-Based Dairy Farm Tile Lines.
Lloyd Owens, USDA-ARS, PO Box 488, Coshocton, OH 43812
Subsurface water quality from agricultural systems varies with the type of system and management. Systems with high inputs from fertilizer and/or manure may have nutrient levels, e.g. NO3-N, in subsurface water. This study investigates the water quality from tile lines on grass-based dairy farms. Monthly samples have been collected and analyzed from 1 to 4 tile lines on 7 grass-based dairy farms in eastern Ohio for more than 1 year. A dry growing season in 2005 limited the number of available samples during that year. Detailed management records often are not available, but preliminary data indicate that NO3-N and PO4-P concentrations in shallow groundwater from grass-based dairy farms are usually at acceptable environmental levels. Nevertheless, if high rates of N fertilizer are applied, e.g. 280 kg ha-1 annually, NO3-N concentrations above 10 mg L-1 are measured. Longer periods of study and data from more farms are needed to confirm the hypothesis that grass-based dairy farms have environmentally sound impacts on groundwater quality.