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Quantifying Diffuse Agricultural Phosphorus Transfers along Hydrological Pathways from Field Scale Studies

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Pp. 169-172 in Preferential Flow, Water Movement and Chemical Transport in the Environment, Proc. 2nd Int. Symp. (3-5 January 2001, Honolulu, Hawaii, USA), eds. D. D. Bosch and K. W. King. St. Joseph, Michigan: ASAE  701P0006.(doi:10.13031/2013.2099)
Authors:   A.I. Fraser, T.R. Harrod and P.M. Haygarth
Keywords:   Phosphorus transfer, agriculture, pathways, eutrophication, diffuse pollution

The control of diffuse phosphorus (P) transfer (PT) from agricultural soils is important in reducing the proliferation of algal scums and other aquatic weeds. This study focused on quantifying the temporal variation in PT from grassland soils along a number of hydrological pathways during winter rainfall. Discharges along hydrological pathways from grassland lysimeters were monitored during the 1996/7 and 1997/8 winters. Greater concentrations were observed in composite flow (overland flow + interflow to 30 cm) and exclusive overland flow discharges, from both the drained and undrained grassland. Total P loads were greater in high intensity rainfall, but low intensity rain (<2 mm hr-1) produced environmentally significant P loads from all pathways. Total P loads were greatest in composite flow and OF from the undrained plot, reaching 1.5 and 4.0 g ha-1 hr-1 respectively. The findings indicate that total water flux along the pathways, rather than TP concentration in discharges, is the primary factor determining the magnitude of PT.

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