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Nutrient Transport in an Agricultural Watershed as Affected By Hydrology

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

Citation:  Paper number  032161,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.13789) @2003
Authors:   J.L. Baker, M.M. Agua, P.A. Lawlor, S.W. Melvin
Keywords:   nitrogen, phosphours, nonpoint pollution, leaching, runoff

Physical and chemical properties of nutrients combined with hydrological factors can dramatically affect nitrogen (N) and phosphorus (P) concentrations in and losses with streamflow from agricultural watersheds. In particular, adsorption and/or solubility of the different nutrient forms affect concentrations in subsurface drainage water, surface runoff water, and sediment in surface runoff. These concentrations, combined with the volumes or masses of subsurface drainage, surface runoff, and sediment, then determine nutrient losses. Data from a watershed study in northeast Iowa illustrate that the soluble, non-adsorbed nature of the nitrate anion results in nitrogen losses being dominated by this form in watersheds where soils and hydrologic conditions result in a significant proportion of streamflow being subsurface drainage. Inorganic P in the way of orthophosphate (PO4), because of its tendency to be adsorbed or precipitated from solution, usually has low concentrations in subsurface drainage and higher concentrations in sediment relative to concentrations in surface runoff water. Therefore watersheds with lower relief and more subsurface drainage generally have lower phosphorus losses than watersheds with steeper more erosive soils and more surface runoff water.

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