TURFGRASS RESPONSE TO NITROGEN SOURCES WITH VARYING NITROGEN RELEASE RATES

There is an interest in lowering turfgrass labor costs by reducing the number of fertilizer applications without negatively affecting turfgrass performance. Many slow or controlled-release nitrogen (N) sources are available, with different N release mechanisms. The objective of this study was to determine if turfgrass quality and clipping production could be maintained while reducing the number of applications with N sources of different release mechanisms. The sites for this field study were a golf course fairway, an unirrigated home lawn, and an irrigated athletic field (no traffic). These sites had different grass species, soil types, and amount of irrigation. The treatments consisted of several slow or controlled-release N sources (polymer coated urea, sulfur coated urea, urea formaldehyde reaction products, and isobutylidene diurea), urea, and an unfertilized control. Slow release fertilizer sources were applied once at the beginning of the year at each of the sites, while urea was applied at the same annual rate, but in 4 to 6 separate applications. Total N applied was 146 kg N ha^-1 yr^-1 for the golf course fairway and home lawn, and 195 kg N ha^-1 yr^-1 for the athletic field. Visual turfgrass quality rankings of slow-release N sources were similar to the urea treatments at all sites. Few differences in visual quality among slow-release sources were detected. Clipping yields closely followed the trends seen in visual quality. These results indicate that several slow-release fertilizers with varying release mechanisms can be used to reduce labor associated with making multiple fertilizer applications.