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Title: PHOSPHORUS CONCENTRATION IN RUNOFF FROM DIVERSE LOCATIONS ON A NEW YORK DAIRY FARM

Author
item Hively, Wells - Dean
item Bryant, Ray
item FAHEY, TIMOTHY - CORNELL UNIVERSITY

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2005
Publication Date: 6/7/2005
Citation: Hively, W.D., Bryant, R.B., Fahey, T.J. 2005. Phosphorus concentration in runoff from diverse locations on a New York dairy farm. Journal of Environmental Quality. 34:1224-1233.

Interpretive Summary: Most water quality studies concerned with nutrient losses from agricultural non-point sources have focused on land use and management practices that are broadly representative of the farm landscape. In this study, simulated rainfall was used to quantify time to runoff, volume and phosphorus (P) concentrations from nine locations representing both spatially extensive field conditions and non-field conditions that are of limited spatial extent on a dairy farm in Delaware County, NY. Runoff from deciduous forest, extensively managed pasture, and two hillside seeps, exhibited low concentrations of total dissolved phosphorus (TDP). Runoff from intensively managed pastures, a hayfield, and a cow path yielded moderate TDP concentrations. A barnyard site with fresh manure deposits produced runoff with extremely high TDP concentrations. Concentrations of suspended solids were relatively low in runoff from vegetated sites, but were higher from sites with little groundcover (barnyard, cow path, plowed maize field). Under dry conditions, as simulated in mid-Summer on day one, time to runoff was shorter (< 23 minutes) for non-field areas (seep areas, barnyard, cow path) than for field areas (27 to 93 minutes). In contrast, under moist conditions, as simulated on day two, time to runoff was <23 minutes for all areas. These results suggest that during the dry summer months, which are characterized by brief, intense thunderstorms, non-field areas of minor spatial extent but with high P concentrations at the soil surface, such as cow paths and barnyards, appear to control TDP loading in streams during runoff events, and this explains the in-stream TDP concentrations that are typically higher by a factor of 3 or 4. Under wet winter and spring conditions, runoff from the extensive field areas dilutes runoff from these high P source non-field areas, resulting in relatively lower TDP concentrations in streams during runoff events. Comprehensive P loss management should address the minor landscape components, such as cow paths and barnyards, in addition to the crop lands and pastures.

Technical Abstract: The National Phosphorus (P) Project rainfall simulator was used to quantify runoff production and P loading at nine locations on a Catskills dairy farm. Observed concentrations of total dissolved phosphorus (TDP) were low (0.007 to 0.12 mg L-1) in runoff from deciduous forest, extensively managed pasture, and two hillside seeps; moderate (0.18 to 0.64 mg L-1) in runoff from intensively managed pastures, a hayfield, and a cow path; and extremely high (11.6 mg L-1) in runoff from a manured barnyard. Concentrations of TDP at sites without fresh manure could be predicted from Morgan’s soil test phosphorus [TDP (mg L-1) = 0.0056 + 0.0180 * STP (mg kg-1); adjusted R2 = 84%]. Observed concentrations of suspended solids were low (16 to 137 mg L-1) in runoff from vegetated sites, but were higher (375 to 615 mg L-1) in runoff from sites with little groundcover (barnyard, cow path, plowed field). Under dry summer conditions time to runoff was shorter (< 18 minutes) for non-field areas (seeps, barnyard, cow path) than for field and forest areas (27 to 93 minutes), but under moist soil conditions time to runoff was uniformly less than 23 minutes. During the dry summer months, non-field areas of minor spatial extent but with high P concentrations at the soil surface (e.g., cow paths and barnyards) appear to control runoff-based TDP loading. During the wet winter months, runoff from fields and forested areas appears to dilute runoff from non-field concentrated sources, resulting in overall lower streamwater TDP concentrations.