Evaluation of organic fertilizer sources for south-eastern (USA) turfgrass maintenance

Although organic fertilizer sources are widely marketed for application to turfgrasses, there is limited research that examines their effect on turfgrass performance in the humid south-eastern United States. For this work, ‘organic’ refers to commercial fertilizers manufactured from wastes such as sewage sludge (biosolid), poultry byproducts (manure, litter, feather meal), or other byproducts (whey, meals, oils). Organic fertilizers can behave as a slow-release N fertilizer, with a delayed greening response, low burn potential, and varying N release rates in different environments. Three separate 3-month long studies (one creeping bentgrass, two hybrid bermudagrass) evaluated the effects of organic fertilizers on various turfgrass and soil parameters. The objectives of this research were to evaluate turfgrass response to organic fertilizers in the field by measuring turf colour, quality, clipping yield, N uptake, total soil microbial biomass, soil inorganic (NO₃-N, NH₄-N), and organic N and carbon content. Organic N sources included materials made from dehydrated biosolids, turkey litter, and meat, bone, blood and feather meal. These sources were compared with hybrid bermudagrass and bentgrass fertilized with urea or a commercial urea/methylene urea fertilizer. All N sources were applied one time each year at a rate of 4.9 g N m⁻². Plots were moved to a new location in each year of the study. In general, application of sources with large portions (or 100%) of soluble N (urea and a urea/methylene urea blend) produced turf with a darker green colour, higher N content, and greater clipping yield than plots fertilized with materials containing organic N. Urea provided consistent high quality colour for the same 10–12 week period as the organic sources, and no organic source provided acceptable colour for any longer period than soluble N sources. There were few differences in soil N, C, or microbial biomass due to N source.