** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** INCREASING PRESSURE OVER WATER RESOURCES IN THE WESTERN U.S. IS FORCING MANY FARMERS IN THIS REGION TO IRRIGATE CROPS WITHOUT MEETING THEIR FULL EVAPOTRANSPIRATION DEMANDS. THIS PRACTICE, KNOWN AS DEFICIT IRRIGATION (DI), CAN LEAD TO SIGNIFICANT YIELD LOSSES UNLESS CROP WATER STRESS LEVELS ARE MAINTAINED WITHIN ACCEPTABLE LEVELS. THE LONG-TERM GOAL OF THIS RESEARCH PROJECT IS TO HELP FARMERS IN THE WESTERN U.S. TO AMELIORATE THE ECONOMIC IMPACT OF PRODUCING CROPS WITH A LIMITED WATER SUPPLY BY IMPROVING A SITE-SPECIFIC IRRIGATION MANAGEMENT DECISION SUPPORT SYSTEM (DSS) THAT CAN BE USED TO ACHIEVE AN EFFECTIVE APPLICATION OF DI LEVELS ESTABLISHED FOR EACH IRRIGATION MANAGEMENT ZONE IN A FIELD. THIS DSS WILL PROVIDE A MUCH-NEEDED ALTERNATIVE TO AVAILABLE COMMERCIAL SOFTWARE DEVELOPED BY IRRIGATION COMPANIES TO GENERATE SITE-SPECIFIC IRRIGATION PRESCRIPTION MAPS. THE INTRINSIC COMPETITIVE NATURE OF SOFTWARE DEVELOPED BY SUCH COMPANIES INFLUENCES THEIR DEVELOPMENT AS 'BLACK-BOXES', WHICH IN TURN PREVENTS THE RIGOROUS ANALYSIS OF THEIR UNDERLYING METHODS AND RESTRICTS THE EVALUATION OF NEW SITE-SPECIFIC IRRIGATION MANAGEMENT STRATEGIES USING COMMERCIAL SOFTWARE.IMPROVEMENTS TO THE DSS TO BE DEVELOPED BY THIS PROJECT CONSIST OF MAKING IT COMPATIBLE WITH ANY TYPE OR BRAND OF CENTER PIVOT OR LINEAR MOVE IRRIGATION SYSTEM WITH VARIABLE RATE IRRIGATION CAPABILITIES AND INCORPORATING INTO ITS SOFTWARE AN INTERFACE TO A CROP WATER USE AND YIELD MODEL. THE RESULTING DSS WILL BE A COMPUTER PROGRAM THAT THE COMMUNITY OF AGRICULTURAL RESEARCHERS, EXTENSIONISTS AND CONSULTANTS CAN USE AS AN OPEN PLATFORM UPON WHICH NOVEL SITE-SPECIFIC IRRIGATION MANAGEMENT STRATEGIES BASED ON SOUND SCIENTIFIC PRINCIPLES CAN BE IMPLEMENTED AND EVALUATED. THE DSS WILL BE EVALUATED WITH ALFALFA, CORN, AND COTTON EXPERIMENTS THAT WILL BE CONDUCTED IN RENO, NV, BUSHLAND, TX, AND DAVIS, CA, RESPECTIVELY. WE'LL RELEASE TO THE PUBLIC THE COMPUTER CODE OF THE DSS SO THAT IT CAN BE IMPROVED OR MODIFIED BY OTHER AGRICULTURAL RESEARCHERS, EXTENSIONISTS AND CONSULTANTS. TRAINING WORKSHOPS WILL BE CONDUCTED TO TEACH THE OPERATION OF THE DSS AND HOW TO MODIFY ITS SOURCE CODE. RESULTS FROM THIS PROJECT WILL BE COMMUNICATED TO STAKEHOLDERS DURING FIELD DAYS ORGANIZED BY PIS AT EACH COLLABORATING LOCATION (RENO, NV, BUSHLAND, TX, AND DAVIS, CA).