Supplemental Nickel Applications and Foliar Urea Fertility On Two Warm-Season Turfgrass Species Under Salinity Stress.

Urea is a popular foliar nitrogen (N) fertilizer in turfgrass management. Before urea can be incorporated into organic N compounds it must be hydrolyzed by urease, a Nickel (Ni) dependent metalloenzyme, into ammonium and carbon dioxide.   Due to the prevalence of foliar urea use in turfgrass management a nine week study repeated twice was conducted at the Clemson University greenhouse facility to examine N metabolism under foliar urea applications and Ni supplementation of two warm-season turfgrass species.  ‘Tif-Eagle’ ultradwarf bermudagrass [Cynondon dactylon (L) Pers. X C. transvaalensis Burtt- Davy] and ‘Diamond’ zoysiagrass [Zoysia matrella (L.) Merr.] were established in solution culture consisting of two levels of salinity (0 and 5,000 ppm NaCl) and three levels of Ni as control, 200, and 400 μg Ni L^-1.  To examine N metabolism and the influence of Ni supplementation on foliar urea fertilization, turfgrass clippings were harvested three times throughout the study to measure urease activity, total amino acid content, tissue nutrient concentration, root mass and clipping yield.  Supplemental Ni applications increased overall urease activity which resulted in elevated amino acid contents in leaf tissue. Although apparent increases in N metabolism and growth were exhibited under Ni supplementation, N concentration in both species decreased over the course of the study.  This is the first research project examining Ni supplementation in turfgrass management.  Further research is needed to further understand the influence of supplemental Ni applications on foliar urea N fertility, micronutrient interactions, and N metabolism.