Two golf course putting green turfgrass responses to urea nitrogen and nickel

Abstract

Urea is a popular foliar nitrogen (N) source in turfgrass (TG) management. Before urea can be assimilated, it must be hydrolyzed by urease, a nickel (Ni) dependent metalloenzyme, into ammonium and carbon dioxide. Due to the prevalence of urea use in TG management and the low use efficiency associated with N fertility, more research is necessary to improve efficiency of foliar applied N. Two experiments were conducted to examine N metabolism under foliar urea fertility and Ni application of two warm‐season TG species. TifEagle ultradwarf bermudagrass [Cynodon dactylon (L) Pers. × C. transvaalensis Burtt‐Davy] and Diamond zoysiagrass [Zoysia matrella (L.) Merr.] were established in solution culture containing three Ni concentrations [Control (tap water), 200, and 400 µg Ni L−1]. Urease activity and amino acid pools were increased under Ni applications, however, an overall decrease in N concentration in leaf tissue was observed over the course of the study. In the second study, TifEagle and Diamond received four Ni concentrations (Control, 400, 800, and 1600 µM supplied as NiCl2) with irrigation to replace evapotranspiration (ET) every 48 h for 6 weeks. The Control turfgrass not receiving Ni had 3 mg kg−1 Ni concentrations in leaf tissue and no toxicity symptoms. Visual toxicity symptoms and growth reductions were observed in TG receiving 400, 800, and 1600 µM Ni regimes which resulted in leaf tissue Ni concentrations of 101, 227, and 420, respectively. There was a reduction in clipping yields from Diamond and TifEagle receiving 1600 µM Ni compared to Control (24.1% and 32.5%, respectively, p < 0.0001 for both), and a significant linear relationship (p = 0.004, R2 = 0.34 and (p < 0.0001, R2 = 0.47, respectively) between Ni concentration and clipping yield. Growth and quality of Diamond and TifEagle declined as leaf tissue Ni concentration surpassed 3 mg kg−1.