Peak Nitrate-Nitrogen Values in Surface Runoff from Fertilized Pastures1
- L. B. Owens,
- W. M. Edwards and
- R. W. Van Keuren2
Pastured watersheds on hill slopes in eastern Ohio were fertilized with ammonium nitrate (NH4NO3) at two different levels for 5 years. The pastures were rotationally grazed during either the growing season (May–October) or the dormant season (November–April). Nitrate-N concentrations were measured in surface runoff events > 0.1 mm from nine watersheds. During the 5-year period, there were 890 runoff events. Sixty-four of these events (7%) had NO3−-N concentrations > 10 mg/L, and 48 of the 64 events occurred within a 30-d period following fertilizer application. Ten events, < 2% of all of the runoff events, exceeded 30 mg/L NO3−-N, and all of these were within 17 d of fertilization. Although all surface runoff events which closely followed fertilizer applications did not have high NO3−-N concentrations, all surface runoff with high NO3−-N was shortly preceded with a fertilizer application. The closeness of the high NO3−-N concentration and fertilizations suggested that fertilizer was the major contributor to high NO3−-N in runoff as opposed to animal waste.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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