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Title: Evaluating Ditch Drainage Control Structure for Mitigating Export of Nitrogen from Agricultural Fields in the Choptank River Watershed

Author
item McCarty, Gregory
item Hively, Wells - Dean
item Sadeghi, Ali
item JORDAN, T - SMITHSONIAN ENV RSCH CTR
item FISHER, T - HORN POINT MARINE LAB

Submitted to: Soil and Water Conservation Society
Publication Type: Abstract Only
Publication Acceptance Date: 7/15/2007
Publication Date: 7/15/2007
Citation: McCarty, G.W., Hively, W.D., Sadeghi, A., Jordan T., Fisher, T. 2007. Evaluating ditch drainage control structures for mitigating export of nitrogen from agricultural fields in the Choptank River Watershed [abstract]. Soil and Water Conservation Society. p. 46.

Interpretive Summary:

Technical Abstract: The Choptank River watershed has an extensive network of agricultural drainage ditches that are significant pathways of nitrogen export from production fields and negatively impact water quality in the Chesapeake Bay. The use of controlled drainage structures on ditches to regulate water flow has been identified as a useful BMP to minimize agricultural nitrogen movement from fields and promote denitrification by increasing the interaction of groundwater nitrate with carbon-enriched ecosystems of the rooting zone. This study involves comparison of ditch sites under existing drainage control with baseline unmanaged ditch sites. Ditches are also being monitored pre- and post- installation of controlled drainage structures to remove inter-site effects. Flux of water and nutrients are being monitored by use automated sampling at weir structures. Measurement of denitrification at the landscape scale involves measurement of dissolved gas in groundwater to detect excess nitrogen gas generated by denitrification as well as N and O isotope composition of remaining nitrate. This is expected to generate a relationship between denitrification and isotope composition. Subsequent measurement of the isotope composition of nitrate in ditch water can provide a landscape scale assessment of nitrate removal by controlled drainage of ditches. Initial results from these studies will be presented.