This legislation, titled the Plant Biostimulant Act of 2025, aims to amend the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) by providing a consistent definition for plant biostimulants . It specifically excludes these substances from the existing definitions of "plant regulator" and "pesticide" under FIFRA, clarifying their regulatory status. The bill defines a plant biostimulant as a substance or mixture that supports a plant's natural processes independently of its nutrient content, thereby improving nutrient availability, stress tolerance, and overall growth or yield. It also introduces definitions for "nutritional chemical" and "vitamin hormone product." The Environmental Protection Agency Administrator is required to revise relevant regulations within 120 days of enactment to incorporate these new definitions. Beyond definitional changes, the bill mandates the Secretary of Agriculture to conduct a comprehensive study on plant biostimulants. This study will assess practices that effectively increase soil organic matter, reduce atmospheric volatilization, promote nutrient management, and limit runoff or leaching of nutrients. Furthermore, it will examine how biostimulants can restore beneficial soil bioactivity, aid in carbon sequestration, improve nutrient use efficiency, and support innovative approaches to agricultural sustainability. The Secretary must make a public report detailing the study's findings and submit it to Congress within two years of receiving funds for the study.