Tryptophan is one of the 22 essential amino acids and serves as a building block for protein synthesis. Tryptophan also is a known precursor for auxin in plants. Previous research has shown that applying fertilizers amended with auxin coming from tryptophan may enhance plant defense chemical responses during limited soil moisture conditions. This occurs through increases in root production, as well as changes in endogenous hormone levels, resulting in plant growth regulating activity. Tryptophan is produced industrially through fermentation, and following that process, a byproduct remains. Tryptophan byproduct (TRP-B) is currently considered a waste product. However, the trace amounts of tryptophan and nitrogen containing compounds remaining in the byproduct following fermentation make it an intriguing subject for use as a growth promoter for turfgrasses. The objective of this research was to determine whether applications of TRP-B improve Penn A-4 creeping bentgrass (Agrostis stolonifera L.) performance more than applications of pure tryptophan and/or urea.