SOIL ORGANIC MATTER REPRESENTS A MAJOR SOURCE AND SINK OF GREENHOUSE GASES AND PLAYS A KEY ROLE IN SOIL HEALTH. BECAUSE SOIL ORGANIC MATTER CONTENT IS POSITIVELY ASSOCIATED WITH CROP YIELD AND YIELD STABILITY, INCREASING SOIL ORGANIC MATTER CAN BENEFIT FARMER INCOME, FOOD SECURITY, AND RESOURCE USE EFFICIENCY WHILE PROVIDING ECOSYSTEM SERVICES LIKE CARBON SEQUESTRATION. THE UNDERSTANDING THAT MOST OF THE ORGANIC MATTER IN SOIL COMES FROM ROOT INPUTS RATHER THAN ABOVEGROUND RESIDUE HAS GENERATED INTEREST IN BREEDING CROPS FOR ORGANIC MATTER-BUILDING ROOT TRAITS. HOWEVER, VARIATION IN THE QUANTITY, CHEMICAL COMPOSITION, AND DISTRIBUTION OF ROOT INPUTS HAS SCARCELY BEEN EVALUATED FOR MAJOR CROP SPECIES AND THE IMPACT OF THESE ROOT TRAITS ON THE FORMATION AND LONG-TERM STABILITY OF SOIL ORGANIC MATTER IS UNCLEAR. THIS INFORMATION IS NEEDED TO DETERMINE THE POTENTIAL FOR, AND PATHWAY TOWARD, ENHANCED ROOT SYSTEMS FOR SOIL HEALTH.THIS PROPOSAL WILL ADVANCE OUR UNDERSTANDING OF HOW ROOT SYSTEM TRAITS IMPACT SOIL ORGNIC MATTER. USING A DIVERSE PANEL OF MAIZE CULTIVARS GROWN IN THE GREENHOUSE, WE PROPOSE TO MEASURE CHANGES IN ROOT TRAITS DUE TO BREEDING OVER THE LAST ~100 YEARS. WE WILL SELECT FOUR CULTIVARS WITH DISTINCT ROOT SYSTEMS FROM THIS PANEL FOR A FIELD STUDY THAT WILL TEST THE EFFECTS OF CULTIVAR, MANAGEMENT, AND ABOVEGROUND RESIDUE REMOVAL ON SOIL ORGANIC MATTER FORMATION. LASTLY, WE WILL INVESTIGATE THE EFFECTS OF ROOT CHEMICAL COMPOSITION ON SOIL ORGANIC MATTER FORMATION IN DIFFERENT SOIL TYPES USING A LABORATORY INCUBATION STUDY. WE WILL COMMUNICATE OUR FINDINGS TO RESEARCHERS, PRODUCERS, STUDENTS, AND THE GENERAL PUBLIC THROUGH PEER-REVIEWED PUBLICATIONS AND POPULAR PRESS ARTICLES AS WELL AS PRESENTATIONS AT SCIENTIFIC MEETINGS, PRODUCER MEETINGS, AND IN THE CLASSROOM. THROUGH THIS RESEARCH, WE EXPECT TO IDENTIFY ROOT TRAITS THAT ENHANCE THE FORMATION AND STABILITY OF SOIL ORGANIC MATTER. THIS OUTCOME IS PROJECTED TO HAVE A POSITIVE IMPACT BY ENABLING PLANT BREEDERS AND AGRONOMISTS TO INTEGRATE ORGANIC MATTER-BUILDING ROOT TRAITS INTO U.S. CROPPING SYSTEMS, ULTIMATELY LEADING TO INCREASED SOIL HEALTH, AGRICULTURAL RESILIENCE, AND AGRICULTURAL SUSTAINABILITY.