Foliar applied urea nitrogen metabolism in warm-season turfgrass under salinity stress

The first study examined the effect of urea fertilization method (root vs. foliar) under salinity stress of five warm-season turfgrasses. We hypothesized that urea delivery method will influence N uptake under salinity stress and the turfgrasses will perform similarly under salinity stress. Treatments included two fertility delivery methods, two salinity levels, and five warm season turfgrass genotypes. Results revealed no difference between root and foliar applications of urea N under salinity stress. Findings from this study suggest that foliar applications of urea N provide an alternative to traditional granular fertilization when root zone salinity is elevated.;The second study examined urea N metabolism and the effect of Ni 2+ supplementation on foliar uptake of urea. We hypothesized that Ni2+ supplementation will enhance urea N metabolism and foliar uptake by stimulating urease activity and increasing total amino acid pools in turfgrass leaf tissue. Treatments included two salinity levels, two turfgrass species and three Ni2+ levels. Results from this study revealed an apparent stimulation of N metabolism under foliar urea nutrition with Ni 2+ supplementation.;The third study further examined Ni2+ toxicity of two common warm-season turfgrasses under urea N fertility. We hypothesized that Ni2+ supplementation will stimulate urease activity and increase amino acid pools as recorded in the previous study. Secondly, as Ni 2+ concentration in leaf tissue increases, toxicity will cause decreases in turf quality, growth, and fluctuations in micronutrient concentration. Treatments included two turfgrass species, and four Ni2+ levels. Results revealed a stimulation of urease activity and increases in the total amino acid pool with Ni2+ supplementation.;An additional fertility delivery method experiment was conducted to examine recovery of 15N following root and foliar applications of urea. We hypothesized that total plant recovery of 15N derived from fertilizer would be different between delivery methods and that overall recovery would be greater in foliar applied treatments. Results revealed that total plant recovery of 15N labeled urea derived from fertilizer was not significantly different in either fertility regime or species tested. Although not statistically different, root applications of urea N resulted in 10% higher total 15N recovery than foliar treatments at 8 hours after application.;Lastly, a field study was conducted to investigate the effects of N fertility levels and plant growth regulator applications on the performance of Diamond zoysiagrass as a putting green surface in the transition zone. We hypothesized that N fertility level and plant growth regulator applications would significantly influence Diamond zoysiagrass putting green performance. Results of this study revealed that Diamond zoysiagrass has the ability to become another warm-season turfgrass option for putting greens in the southern transition zone. Based on finding of this project, N fertilization of Diamond zoysiagrass in putting green scenarios should begin with 147 kg-1 N ha-1 or less over the growing season. Additional quick release N sources should be used following cultivation events to promote growth and recovery. (Abstract shortened by UMI.).