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United States Department of Agriculture

Agricultural Research Service

Title: An Innovative Approach for Locating and Evaluating Subsurface Losses of Nitrogen

Authors
item Walthall, Charles
item Kung, K.J. - UNIVERSITY OF WI
item Mcarty, G. - USDA-ARS
item Timlin, D. - USDA-ARS ALTERNATIVE CROP
item Angier, J. - USDA-ARS
item Buss, P. - USDA-ARS

Submitted to: Nitrogen Environment and People Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 14, 2001
Publication Date: N/A

Interpretive Summary: Fundamental watershed-scale processes governing chemical flux to neighbori ecosystems are so poorly understood that effective strategies for mitigatin chemical contamination cannot be formulated. Characterization of evapotranspiration, surface runoff, plant uptake, subsurface preferential flow, behavior of the chemicals in neighboring ecosystems and an understanding of how crop management practices influence the processes are needed. Adequate characterization of subsurface flow has been especially difficult because conventional sampling methods are ineffective for measuri preferential flow of water and solutes. A sampling strategy based on ground penetrating radar mapping of subsurface structures coupled with near-real time soil moisture data, surface topography, remotely sensed imagery and a geographic information system appear to offer a means of accurately identifying subsurface preferential flow pathways. Four small adjacent watersheds draining into a riparian wetland and first order stream at the USDA-ARS Beltsville Agricultural Research Center, Beltsville, Maryland are being studied with this protocol. The spatial location of some of the preferential flow pathways for chemicals exiting these agricultural watersheds to the neighboring ecosystems have been identified. These result will be presented with a description of the broader objectives of the experiments at the site.

Technical Abstract: Fundamental watershed-scale processes governing chemical flux to neighbori ecosystems are so poorly understood that effective strategies for mitigatin chemical contamination cannot be formulated. Characterization of evapotranspiration, surface runoff, plant uptake, subsurface preferential flow, behavior of the chemicals in neighboring ecosystems and an understanding of how crop management practices influence the processes are needed. Adequate characterization of subsurface flow has been especially difficult because conventional sampling methods are ineffective for measuri preferential flow of water and solutes. A sampling strategy based on ground penetrating radar mapping of subsurface structures coupled with near-real time soil moisture data, surface topography, remotely sensed imagery and a geographic information system appear to offer a means of accurately identifying subsurface preferential flow pathways. Four small adjacent watersheds draining into a riparian wetland and first order stream at the USDA-ARS Beltsville Agricultural Research Center, Beltsville, Maryland are being studied with this protocol. The spatial location of some of the preferential flow pathways for chemicals exiting these agricultural watersheds to the neighboring ecosystems have been identified. These result will be presented with a description of the broader objectives of the experiments at the site.

Last Modified: 4/20/2014