Measuring biomass in grassland ecosystems may be difficult, labor intensive and unreliable due to spatial variability and pasture size. Normalized difference vegetative index(NDVI) determined by a satellite, aircraft or ground based sensors may offer a quick and reliable way to determine biomass in grasslands. Five rates of aqueous nitrogen (28% w/w) were applied to an endophyte-free tall fescue (Festuca arundiacea cv Select) sward in a randomized complete block design to determine the relationship between NDVI and herbage biomass.