** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** CROP ROTATION IS ONE OF THE FEW SUSTAINABLE AGRICULTURAL PRACTICES THAT CAN MAINTAIN LONG-TERM CROP YIELDS. HOWEVER, THERE IS NO SYSTEMATIC METHODOLOGY TO OPTIMIZE CROP ROTATION SEQUENCES FOR BOTH YIELDS AND SUSTAINABILITY GOALS. WE PROPOSE TO TEST A NOVEL APPROACH TO DETERMINE OPTIMAL CROP ROTATION SEQUENCES BY INCORPORATING PLANT-SOIL FEEDBACK (PSF), A MAJOR ECOLOGICAL PROCESS DEFINED AS THE EFFECT OF A PRECEDING CROP ON THE PRODUCTIVITY OF A SUBSEQUENT CROP RESULTING FROM SOIL BIOTIC AND ABIOTIC LEGACIES. THE MAJOR FACTORS DRIVING PSF INCLUDE PATHOGENS, MUTUALISTS, NUTRIENTS, AND DEPOSITION OF SECONDARY CHEMICALS. GIVEN THE CURRENT MAJOR EMPHASIS ON DEVELOPING AGRONOMIC PRACTICES THAT REDUCE INPUTS AND MAINTAIN SOIL HEALTH, THIS RESEARCH PROPOSAL IS AN OPPORTUNITY TO APPLY THE PSF FRAMEWORK TO AGRICULTURAL CROP PRODUCTION. OUR PROPOSAL HAS THREE COMPONENTS: 1) A GREENHOUSE POT EXPERIMENT TO INVESTIGATE EFFECTS OF PSF ON CROP BIOMASS USING FOUR GLOBALLY SIGNIFICANT CASH CROPS (CANOLA, MAIZE, SOYBEAN AND WHEAT), 2) A FIELD EXPERIMENT TO VERIFY THE RESULTS FROM THE GREENHOUSE EXPERIMENT, AND 3) EXPLORING MECHANISMS OF PSF EFFECTS ON CROP GROWTH USING STRUCTURAL EQUATION MODELING. BOTH EXPERIMENTS CONSIST OF A TRAINING PHASE AND TWO FEEDBACK PHASES. MEASUREMENTS INCLUDE PLANT BIOMASS, CROP YIELDS, FOLIAR NUTRIENTS, SOIL AND ROOT MICROBIOMES, SOIL MICROBIAL HEALTH INDICES AND SOIL AGGREGATE STABILITY. WE AIM TO DETERMINE 1) HOW CROP DIVERSIFICATION AND SEQUENCE IN ROTATIONS AFFECT CROP YIELDS AND SOIL HEALTH, AND 2) THE ROLES OF SOIL MICROBIAL COMMUNITIES ON CROP ROTATION PERFORMANCE, THE TWO MAJOR GOALS OF FOUNDATIONAL KNOWLEDGE OF AGRICULTURAL PRODUCTION SYSTEMS.