Consumer demand for cleaned squid generates a substantial amount of waste that must be properly disposed of, creating an economic burden on processors. A potential solution to this problem involves converting squid byproducts into an organic fertilizer, for which there is growing consumer demand. Organic fertilizers are reputed to offer advantages that synthetic fertilizers cannot provide, such as increasing soil water- and nutrient-holding capacity and promoting the growth of beneficial soil organisms. To evaluate the effectiveness of hydrolyzed squid waste as an organic fertilizer, we quantified soil fertility and turfgrass quality on perennial ryegrass turf (Lolium perenne L.) amended with two types of fertilizer: squid-based (SQ) or synthetic (SY). Field plots were established on an Enfield silt loam in Kingston, RI, and liquid (L) or granular (G) fertilizer formulations of squid or synthetic fertilizers were applied at 0, 48, 146, and 292 kg nitrogen/ha/year. Soil physical, chemical, and biological properties were determined monthly and turfgrass quality was determined periodically during the growing season in 2008 and 2009. Squid hydrolysate applied as a liquid (SQL) and granular (SQG) fertilizer consistently provided high-quality, uniform turf when compared with synthetic fertilizer applied at the same rate. Soil concentrations of NO3, NH4, PO4, pH, moisture, soil organic matter, C:N ratio, and levels of trace metals were unaffected by fertilizer type, formulation, or rate throughout the two-year study. Both squid-based organic fertilizer formulations gave significantly higher microbial activity rates than their synthetic counterparts regardless of application rate. Conversion of squid processing byproducts into fertilizer has the potential to improve turfgrass quality while providing a sustainable solution to waste disposal problems in the seafood processing industry.