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Title:   Author  item
                                            Gish, Timothyitem
                                            PACHEPSKY, Y - ENVIRONMENTAL MICROBIALitem
                                            McCarty, Gregoryitem
                                            NICHOLSON, T - US-NRCitem
                                            CADY, R - US-NRCitem
                                            GUBER, A - UNIVERSITY OF CALIFORNIA
  Submitted to: Geological Society of America Meeting
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 8/15/2006
                                    Publication  Date: 9/15/2006
                                    Citation: Gish, T.J., Pachepsky, Y.A., McCarty, G.W., Nicholson, T.J., Cady, R.E., Guber, A.K. 2006. Quantifying subsurface hydrology with ground penetration radar and agricultural monitoring data [abstract]. Geological Society of America. p. 197.Interpretive Summary:
                                Technical Abstract: Hydrology, especially subsurface-water flow can influence crop growth patterns within a production field as well as the fate of surface-applied fertilizers and pesticides migrating thru agricultural land.  Ground-penetrating radar (GPR) and digital elevation maps (DEM) were used to locate and quantify subsurface flow where water appears to have converged into discrete subsurface pathways.  Yield and soil moisture observations in a 3.2 ha field and water and chemical flows in a neighboring stream into which the field drains were used to confirm the existence of these subsurface flow pathways.  Results showed that corn grain yields during a drought year decreased with increasing distance from the GPR-identified subsurface-flow pathways.  Soil-water contents for three consecutive growing seasons demonstrated a consistent decrease in soil-water content with increasing distance from the GPR-identified subsurface-flow pathway. In addition, the movement of agricultural chemicals in discrete subsurface channels through the riparian area is supported by the observed nitrate concentrations and nitrate fluxes in the which increased with increasing base-flows.  This research suggests that subsurface flow pathways exist, and can have a dramatic impact on production, as well as the quality of water exiting land with this climate and type of soil morphology.


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