AGRICULTURAL SOILS IN THE SOUTHEASTERN U.S., MARKED BY HIGH RAINFALL AND WARM TEMPERATURES, ARE OFTEN CHARACTERIZED WITH LOW ORGANIC C AND SOIL PH (I.E., ACIDIC SOIL). ORGANIC FARMING RELIES ON ORGANIC INPUTS AND FUNDAMENTALLY ALTERS THE SOURCES AND FORMS OF REACTIVE CARBON (C) AND NITROGEN (N) INPUTS. IT ALSO INDUCES CHANGES IN SOIL PHYSICAL AND GEOCHEMICAL PROPERTIES THAT MAY PROFOUNDLY AFFECT THE ABUNDANCES, COMPOSITION AND ACTIVITIES OF SOIL MICROBES, INCLUDING NITRIFIERS (I.E., AMMONIA-OXIDIZING BACTERIA AND ARCHAEA) AND DIVERSE TYPES OF DENITRIFIERS. HOWEVER, THERE IS STILL A LACK OF A HOLISTIC PICTURE OF ORGANIC FARMING EFFECTS ON N-CYCLING MICROBES AND THEIR ACTIVITIES. WE HYPOTHESIZE THAT ORGANIC FARMING, IF PROPERLY ADOPTED, MAY INDUCE CONSISTENT AND PREDICTABLE CHANGES TO FOSTER THE DEVELOPMENT OF MICROBIAL COMMUNITIES FOR N RETENTION AND MITIGATION OF EMISSIONS OF TRACE GAS, N2O. WE PLAN TO TEST OUR THREE SPECIFIC HYPOTHESES ON LONG-TERM (19-YR) CROPPING SYSTEMS AT THE CENTER FOR ENVIRONMENTAL FARMING SYSTEMS (GOLDSBORO, NC) AS WELL AS ON MULTIPLE ORGANIC FARMS ACROSS NORTH CAROLINA. THREE MAJOR QUESTIONS WILL GUIDE OUR PROPOSED RESEARCH: 1) DOES LONG-TERM ORGANIC FARMING CAUSE CONSISTENT, PREDICTABLE SHIFTS IN N-CYCLING MICROBES ACROSS DIFFERENT SOILS? 2) WHAT ARE THE PRIMARY DRIVERS AND/OR ENVIRONMENTAL FACTORS THAT AFFECT THE COMPOSITION AND ACTIVITIES OF N-CYCLING MICROBES? 3) TO WHAT EXTENT DO CHANGES IN N-CYCLING MICROBES ALTER N RETENTION IN PLANT-SOIL SYSTEMS AND N2O EMISSIONS? ANSWERING THESE QUESTIONS WILL ADVANCE UNDERSTANDING OF N TRANSFORMATIONS IN ORGANIC SYSTEMS AND FACILITATE DEVELOPMENT OF MANAGEMENT REGIMES THAT ENHANCE N USE EFFICIENCY AND ECOSYSTEM N RETENTION, WHILE REDUCING N2O EMISSIONS.