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Title: Relating nutrient and herbicide fate with landscape features and characteristics of 15 subwatersheds in the Choptank River Watershed

Author
item Hively, Wells - Dean
item Hapeman, Cathleen
item FISHER, THOMAS - UNIV MD
item Rice, Clifford
item McCarty, Gregory
item McConnell, Laura
item Downey, Peter
item NINO DE GUZMAN, GABRIELA - UNIV MD
item Bialek Kalinski, Krystyna
item Lang, Megan

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2011
Publication Date: 8/1/2011
Citation: Hively, W.D., Hapeman, C.J., Fisher, T.R., Rice, C., Mccarty, G.W., Mcconnell, L.L., Downey, P.M., Nino De Guzman, G., Bialek Kalinski, K.M., Lang, M.W. 2011. Relating nutrient and herbicide fate with landscape features and characteristics of 15 subwatersheds in the Choptank River Watershed. Journal of Agriculture and Food Chemistry. 409:3866-3878.

Interpretive Summary: The Choptank River is an estuary and tributary on the eastern shore of the Chesapeake Bay; it drains portions of the Delmarva Peninsula, located within the Mid-Atlantic region of the United States. Its watershed is an ARS Benchmark Watershed in the Conservation Effects Assessment Project (CEAP). Samples were collected monthly from 15 subwatersheds in the northern part of the Choptank River and the concentrations were determined for nutrients, herbicides, and several degradation products. Digital imagery was used to quantify land uses within each subwatershed. Seasonal changes were observed for atrazine and metolachlor concentrations, while the nutrient and degradation product concentrations were more highly influenced by subwatershed itself. As expected, larger amounts of nutrients and herbicides were delivered from subwatersheds with the greatest amount of agricultural land use. The highest loading rates were found in subwatersheds where the percentage of forest and forested wetlands was low relative to the percentage of agricultural lands. These results will assist land managers with identifying areas where conservation practices are working and in targeting areas where changes in management practices will yield the most benefit.

Technical Abstract: The Choptank River is an estuary and tributary on the eastern shore of the Chesapeake Bay; it drains portions of the Delmarva Peninsula, located within the Mid-Atlantic region of the United States. Its watershed is an ARS Benchmark Watershed in the Conservation Effects Assessment Project (CEAP). Monthly base flow concentrations of 15 subwatersheds in the northern part of the Choptank River were determined for nitrate, orthophosphate, atrazine, CIAT, CEAT, metolachlor, and MESA. High resolution geospatial coverage of each subwatershed was characterized using National Aerial Photography Program digital orthophoto quad imagery. Seasonal changes were observed for atrazine and metolachlor concentrations, while the nutrient and degradation product concentrations were more highly influenced by subwatershed. As expected, larger annual loads were generally associated with greater hectares of agricultural land use within the subwatershed. However, the highest loading rates for nitrate and the herbicide degradation products were found in subwatersheds where the percentage of forest and forested wetlands was low relative to the percentage of agricultural lands. These results will assist land managers in targeting areas where changes in management practices will yield the most benefit.