1a. Objectives (from AD-416):
Characterize the spatial and temporal distribution and co-occurrence of Pseudo-nitzschia sp., domoic acid, urea, and other water quality parameters in relation to surrounding land use to identify probable terrestrial sources of urea in the Manokin River watershed; 2) Determine the effects of agricultural practices on the concentration and distribution of urea entering the surface waters of the Manokin River watershed; 3) Provide educational opportunities to undergraduate and graduate students.
1b. Approach (from AD-416):
Water samples for Pseudo-nitzschia, domoic acid, urea, and other water quality parameters will be collected from 25 selected sites throughout the Maryland Manokin River Watershed. Synoptic water sampling at these sites will be conducted to evaluate concentrations of these water quality parameters and correlations with land-use, time of year, and hydrology. In-stream processing of urea will be evaluated experimentally using standard solute injection techniques. In an exploratory study, we will work with the SPAtially-Referenced Regression on Watershed attributes (SPARROW) model to gain a better understanding of the importance of land-use and in-stream processing on urea export from the Manokin River watershed. Commercial fertilizer or poultry litter use will be documented and spatially characterized throughout the Manokin River watershed. Rainfall simulation studies will be conducted to assess interactions between soil, nitrogen source, and timing/sequence of runoff event on urea losses in runoff using an established indoor runoff box protocol. Column leaching studies will be conducted to assess interactions between soil, nitrogen source, and leaching of urea. Plot and field scale monitoring studies will evaluate fate and transport of urea from agricultural fields to drainage ditches. Graduate and undergraduate students will participate in all aspects of the research.
3. Progress Report:
This collaboratively developed Capacity Building Grant supports one UMES PhD student and one Penn State Master’s student studying urea fate and transport in the Manokin River. We continued sampling 16 sites (10 nontidal and 6 tidal) throughout the basin and sampled 8 sites on the main stem of the Manokin River. Efforts focused on collecting routine monthly water samples from all sites, as well as conducting targeted storm event sampling on selected sites. Results from the 2011 campaign were featured in several presentations at national meetings, including the American Geophysical Union Fall Meeting (2011) and Biogeomon (2012). These results are currently being summarized, and will be submitted to peer-reviewed journals for publication. Runoff boxes packed with soil collected from the University of Maryland Eastern Shore (UMES) Research and Teaching Farm and amended with seven N fertilizer and manure treatments were subjected to simulated rainfall. Data are currently being summarized by a PhD candidate at UMES. Nitrogen leaching losses from fertilizer treatments were measured in field lysimeters installed at UMES. Extremely dry weather conditions did not produce leachate. The plots were sprinkler irrigated following a split rate application of the nitrogen treatments in July, and leachate samples were collected. Following heavy rains after initial fertilization and planting, soil cores were collected from field plots under various nitrogen fertilizer source treatments. Urea was detected at depth, but variability in depth trends suggests urea movement through macropores.