THIS REGIONAL PROJECT WILL ASSESS IMPROVED COVER CROP (CC) MANAGEMENT STRATEGIES TO MAXIMIZE CC YIELDS FOR BIOFUEL PRODUCTION ACROSS A PRECIPITATION GRADIENT. STUDIES EVALUATING CC BIOMASS YIELD AS BIOFUEL FEEDSTOCK ARE VERY LIMITED. THE FEW STUDIES SUGGEST THAT CC HAVE THE POTENTIAL TO PRODUCE SUFFICIENT BIOMASS FOR BIOFUEL, DEPENDING ON THE REGION. COVER CROPS MAY REDUCE PRIMARY CROP YIELDS IN SEMIARID LOCATIONS BECAUSE THEY USE WATER, RESULTING IN REDUCED YIELDS OF THE PRIMARY CROP. INNOVATIVE STRATEGIES SUCH AS CC PLANTING OR TERMINATION TIME OR IMPROVED ROTATIONS COULD ALLOW SUFFICIENT CC BIOMASS PRODUCTION WHILE MAINTAINING OR INCREASING PRIMARY CROP YIELD. THIS PROJECT WILL DETERMINE THE BEST MANAGEMENT PRACTICES FOR BALANCING CC BIOMASS YIELD PRODUCTION FOR BIOFUEL AS WELL AS THE SUSTAINABILITY OF THE PRIMARY CROP PRODUCTION. IT WILL ALSO ESTIMATE CC BIOMASS PRODUCTION ON A LARGE SCALE AND DETERMINE THE ECONOMIC AND SOCIAL FEASIBILITY OF CC USE FOR BIOFUEL ACROSS A PRECIPITATION GRADIENT.THIS PROJECT WILL BE CONDUCTED ACROSS A PRECIPITATION, SOIL TEXTURE, AND ELEVATION GRADIENT IN NEBRASKA. THIS PROJECT WILL BE CONDUCTED IN THREE PHASES. THE FIRST PHASE WILL ASSESS CC MANAGEMENT STRATEGIES THAT MAXIMIZE CC BIOMASS YIELD WITHOUT NEGATIVELY IMPACTING PRIMARY CROP YIELDS. THIS PHASE WILL BE ACCOMPLISHED BY ASSESSING THE INFLUENCE OF CC TERMINATION AND PLANTING DATE ON CC BIOMASS YIELD IN RAINFED VERSUS IRRIGATED SITES IN NEBRASKA. COVER CROP BIOMASS YIELD WILL ALSO BE ASSESSED FOLLOWING CORN SILAGE OR WHEAT ROTATIONS. THE FIRST PHASE WILL ASSESS BOTH CC BIOMASS YIELD AND THE IMPACTS OF THE CC MANAGEMENT STRATEGY ON THE YIELD AND QUALITY OF THE PRIMARY CROP. WE WILL ALSO ASSESS THE EFFECTS OF THE CC MANAGEMENT STRATEGIES ON SOIL WATER CONTENT AND SOIL FERTILITY IN SOIL SAMPLES COLLECTED AT THE TIME OF CC TERMINATION. THE SECOND PHASE WILL CALIBRATE AND VALIDATE A CROP MODEL TO ESTIMATE THE POTENTIAL CC BIOMASS PRODUCTION ON A REGIONAL SCALE USING VARIOUS CROPPING SYSTEMS. WITHIN THIS PHASE, WE WILL ALSO DETERMINE THE MINIMUM CUMULATIVE RAINFALL REQUIRED TO GROW SUFFICIENT CC FOR BOTH RAINFED AND IRRIGATED LOCATIONS. THE THIRD PHASE WILL ASSESS THE ECONOMIC FEASIBILITY AND SOCIAL ASPECTS OF GROWING CC FOR BIOFUEL ACROSS VARYING PRECIPITATION REGIMES. BALANCE BETWEEN COSTS AND GROSS PROFIT WILL BE ASSESSED TO DETERMINE THE ECONOMIC FEASIBILITY. PRODUCERS WILL COMPLETE A SURVEY ABOUT THEIR PERCEPTIONS OF CC USE FOR BIOFUEL AND HOW THEY MAY USE THE STRATEGIES FROM THIS PROJECT ON THEIR FARM.THE ULTIMATE GOAL OF THIS PROJECT IS TO DEVELOP CC MANAGEMENT STRATEGIES FOR BIOFUEL THAT PROMOTE AGRONOMICALLY FEASIBLE, ECONOMICALLY SOUND, AND ENVIRONMENTALLY VIABLE AGRICULTURAL SYSTEMS. FARMERS, EXTENSION AGENTS, AND OTHERS WILL HAVE DATA AVAILABLE TO FACILITATE THE DECISION-MAKING PROCESS ABOUT HOW TO BEST INCORPORATE CC INTO THEIR MANAGEMENT UNDER DIFFERENT SOIL TYPES, CROPPING SYSTEMS, AND PRECIPITATION ZONES. CONFERENCES AND FIELD DAYS WILL ALLOW DIRECT CONTACT WITH PRODUCERS AND PRACTITIONERS TO DISCUSS THE ECONOMIC, ENVIRONMENTAL, AND PRACTICAL ASPECTS OF INCLUDING CC FOR BIOFUEL IN THEIR CROPPING SYSTEMS. SUCCESSFUL IMPLEMENTATION OF STRATEGIES FOR MANAGING CC BIOMASS WILL RESULT IN GREATER QUANTITIES OF FEEDSTOCKS FOR BIOFUEL PRODUCTION, THEREBY REDUCING DEPENDENCE ON FOSSIL FUELS. FURTHER, BECAUSE CC GENERALLY HAVE POSITIVE EFFECTS ON SOIL PROPERTIES, THE VALUE-ADDED BENEFITS OF ENHANCED SOIL NUTRIENT CYCLING, IMPROVED SOIL STRUCTURE, PREVENTION OF SOIL EROSION, AND CARBON SEQUESTRATION ARE EXPECTED AS SOCIETAL BENEFITS.