THIS INTEGRATED RESEARCH AND EXTENSION PROJECT ADDRESSES STAKEHOLDER CONCERNS ABOUT SUBSURFACE PHOSPHORUS (P) ASSESSMENT. WE SEEK TO EVALUATE LARGE-SCALE GEOPHYSICS AS AN INNOVATIVE TOOL FOR PREDICTING SUBSOIL PROPERTIES THAT GIVE RISE TO CRITICAL SOURCE AREAS OF SUBSURFACE P LOSS. THE NEAR-TERM GOAL OF THE PROPOSED RESEARCH IS TO ADVANCE THE PRECISION OF SUBSURFACE P MANAGEMENT WITH P SITE ASSESSMENT TOOLS THROUGH THE USE OF PLOT- AND LARGE-SCALE GEOPHYSICAL SURVEYS THAT OFFER GREATER INSIGHT INTO THE SUBSURFACE TRANSPORT POTENTIAL OF ARTIFICIALLY-DRAINED AGRICULTURAL FIELDS. OUR LONG-TERM GOAL IS TO FOSTER A STAKEHOLDER-DRIVEN PROCESS THAT WILL ENABLE LARGE-GEOPHYSICAL SURVEYS TO NOT ONLY IMPROVE P USE EFFICIENCY, BUT ALSO ENHANCE WATER QUALITY AND INCREASE YIELDS ON THE DELMARVA PENINSULA AND SIMILAR AGROECOSYSTEMS WITH ARTIFICIAL DRAINAGE. THE RESEARCH WILL TAKE PLACE IN SELECTED AGRICULTURAL FIELDS ON THE DELMARVA PENINSULA, WHICH IS A REGION THAT BEST REPRESENTS THE CHALLENGES OF CONTROLLING P LOSSES IN AREA WHERE SUBSURFACE FLOWS DRIVE P TRANSFERS TO SURFACE WATERS. WE WILL: 1) CARRY OUT LARGE-SCALE GEOPHYSICAL SURVEYS OF TEN OR MORE REPRESENTATIVE FIELDS TO MAP THE STRUCTURAL PROPERTIES OF TOPSOILS AND DEEPER SOIL LAYERS AFFECTING SUBSURFACE TRANSPORT AND HYDROLOGIC CONNECTIVITY; 2) SELECT THREE TO FIVE FIELDS AND CONDUCT PLOT-SCALE SPRINKLING EXPERIMENTS WITH COUPLED ELECTRICAL/HYDROLOGICAL TRACER MONITORING STRATEGIES TO EVALUATE AND VERIFY CRITICAL SOURCE AREAS OF SUBSURFACE TRANSPORT MAPPED USING LARGE-SCALE GEOPHYSICAL SURVEYS; AND 3) CONDUCT EXTENSION PROGRAMS TO DEMONSTRATE THE VALUE OF USING LARGE-SCALE GEOPHYSICAL SURVEYS TO DRIVE SITE-SPECIFIC AGRONOMIC MANAGEMENT AND CONSERVATION.