** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** PLASTIC WASTE HAS INUNDATED ECOSYSTEMS AROUND THE WORLD, AND SOILS ARE PARTICULARLY THREATENED BY THIS SEEMINGLY UBIQUITOUS POLLUTION. PLASTIC FILM MULCHES USED IN MANY CROPPING SYSTEMS ARE CONTRIBUTING TO SOIL PLASTIC POLLUTION: MOST ARE MADE OF POLYETHYLENE (PE), WHICH IS POORLY DEGRADABLE, AND LEAVES FRAGMENTS IN SOILS FOR LONG PERIODS. BIODEGRADABLE PLASTIC MULCH FILMS (BDMS) ARE AN ALTERNATIVE, MEANT TO BE TILLED INTO SOIL AFTER USE AND DEGRADED BY MICROORGANISMS. PLASTIC FILM REMNANTS BREAK DOWN INTO MICROSCOPIC PIECES, OR MICROPLASTICS, WHICH ARE ACCUMULATING IN AGRICULTURAL SOILS. EVIDENCE CONTINUES TO BUILD THAT SOIL BIOTA INTERACT WITH MICROPLASTICS WITH DETRIMENTAL EFFECTS. HOWEVER, THE LIMITED RESEARCH TO DATE HAS FOCUSED ON CONVENTIONAL (I.E. NON-BIODEGRADABLE) PLASTICS; IMPACTS OF BIODEGRADABLE MICROPLASTICS ARE UNKNOWN. ALTHOUGH MICROPLASTICS DERIVED FROM BIODEGRADABLE PLASTIC FILMS WILL ULTIMATELY MINERALIZE, THEY STILL RESIDE IN SOIL FOR SEVERAL WEEKS TO MONTHS. THUS,SOIL BIOTA ARE EXPOSED TO BIODEGRADABLE MICROPLASTICS IN POTENTIALLY HIGH CONCENTRATIONS, ESPECIALLY FOLLOWING TILL-DOWN OF BDMS. OUR OVERARCHING GOAL IS TO REVEAL IMPACTS OF BOTH CONVENTIONAL AND BIODEGRADABLE MICROPLASTICS AND NANOPLASTICS ON SOIL BIOTA AND THEIR FUNCTIONS TO BETTER ASSESS HOW PLASTIC POLLUTION AFFECTS SOIL HEALTH. OUR DRIVING QUESTIONS ARE: 1) HOW DO MICROPLASTICS AFFECT MICROBIAL AND MICROFAUNAL COMMUNITIES AND THEIR FUNCTIONALITY?; AND 2) DO THESE IMPACTS DIFFER BETWEEN CONVENTIONAL PE FILMS AND BIODEGRADABLE PLASTIC FILMS? OUR PROPOSED RESEARCH WILL USE AGRICULTURALLY-RELEVANT MICROPLASTIC FRAGMENTS TO INVESTIGATE EFFECTS OF PE AND BDM MICROPLASTICS ON SOIL ORGANISMS, POPULATIONS AND COMMUNITIES IN TERMS OF PHYSIOLOGY, DIVERSITY, STRUCTURE, AND THEIR CONTRIBUTIONS TO CRITICAL SOIL FUNCTIONS.