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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 9/10/2005 Publication Date: 11/7/2005 Citation: Hively, W.D. 2005. Characterization of phosphorus loading source areas in a monitored dairy farm landscape, five years after implementation of best management practices [abstract]. American Water Resources Association International Annual Conference. 2005 CDROM. Interpretive Summary: Technical Abstract: Two years of field data collection, along with ongoing site records, provided the basis for characterization of phosphorus (P) loading source areas throughout a 160-ha monitored dairy farm watershed located in the headwaters of Cannonsville Reservoir, a New York City (NYC) drinking water supply. Best management practices (BMPs) that were implemented on the farm using the NYC Watershed Agricultural Program’s Whole Farm Planning process resulted in a 43% reduction in watershed TDP loading over a four-year monitoring period (1), but at the time of sampling it was evident that several P loading problem areas remained. A program of soil and water sampling was therefore employed to characterize P loading sources and processes throughout the landscape. Grabsamples (n=75) of surface runoff and stream flow were collected at various locations throughout the farm during baseflow, rainfall, and snowmelt. Observed runoff concentrations of total dissolved phosphorus (TDP) were elevated at near-barn locations, roadways, and tile drains; were moderate at intensively managed field locations; and were low at extensively managed and forested upper-watershed locations. Soil samples (n=78) were collected throughout the watershed at field and non-field locations. Soil test phosphorus (STP), which rainfall simulation had shown to correlate with TDP concentrations in surface runoff (2), generally increased with proximity to the barn and with frequency of manure application. Only near-barnyard soils exhibited excessive levels of STP. Stream sediment samples (n=41) exhibited low STP in upper stream reaches, with increasing P enrichment in the lower watershed and downstream from the barnyard. Sample results assisted in the development of P extraction coefficients for landscape types throughout the farm watershed that were used for hydrological modeling of TDP loading processes (3,4). Additionally, field observations were used to characterize the magnitude of P load contributions from ten specific source areas including roadways, barnyards, barnyard filter areas, stream crossings, wetlands, and forests. A second round of BMPs, implemented in 2002-2003, have since corrected many of the identified P loading problem areas. |
