Phosphorus Concentrations in Overland Flow from Diverse Locations on a New York Dairy Farm
- W. Dean Hively *a,
- Ray B. Bryantb and
- Timothy J. Faheya
The National Phosphorus Project rainfall simulator was used to quantify overland flow and P transport from nine sites distributed throughout the watershed of a New York City Watershed Agriculture Program collaborating dairy farm. Observed concentrations of total dissolved phosphorus (TDP) were low (0.007–0.12 mg L−1) in flow from deciduous forest, extensively managed pasture, and hillside seeps; moderate (0.18–0.64 mg L−1) in flow from intensively managed pastures, a hayfield, and a cow path; and extremely high (11.6 mg L−1) in flow from a manured barnyard. Concentrations of TDP from sites without fresh manure were strongly correlated with soil test P (TDP [mg L−1] = 0.0056 + 0.0180 × Morgan's soil test phosphorus [STP, mg kg−1]; R 2 = 84%). Observed concentrations of suspended solids were low (16–137 mg L−1) in flow from vegetated sites, but were higher (375–615 mg L−1) in flow from sites with little ground cover (barnyard, cow path, plowed field). Under dry summer conditions the time to observed overland flow was shorter (<18 min) for nonfield areas (seeps, barnyard, cow path) than for field and forest areas (27–93 min), indicating that hydrologically active nonfield areas of minor spatial extent but with high soil P (e.g., cow paths and barnyards) can play a significant role in summertime P loading. When soils started from field capacity (second-day) time to overland flow was uniformly less than 23 min, indicating that under wet watershed conditions low-P source areas can dilute overland flow from concentrated sources.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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