This regulation establishes a tolerance for residues of prohexadione calcium (calcium 3-oxido-5-oxo-4-propionylcyclohex-3- enecarboxylate) in or on grass forage, grass hay, grass straw and grass seed screenings. K-I Chemical U.S.A. Inc. requested these tolerances under the Federal Food, Drug, and Cosmetic Act, as amended by the Food Quality Protection Act of 1996.