Supplemental Nickel Applications and Foliar Urea Fertility On Two Warm Season Turfgrasses Under Salinity Stress.

The relationship of urea and urease activity remains unclear for warm-season turfgrass nitrogen metabolism with urea as a major foliar applied nitrogen source under stressful conditions.  Therefore, a study examining the nitrogen metabolism of two warm season turfgrasses was conducted from May – August 2011 and repeated July -October 2011 in the greenhouse facilities at Clemson University.  ‘Diamond’ zoysiagrass  (Zoysia matrella (L.) Merr.) and ‘TifEagle’ bermudagrass (Cynodon dactylon (L.) Pers. X C. transvaalensis Burtt-Davy) were established for five weeks in hydroponic culture from plugs harvested at the university research turfgrass plots.  Nitrogen was removed from the hydroponic solution during the eight week study.  Treatments consisted of two salinity levels (0 and 5,000 ppm NaCl) and three nickel levels (Control, 200 µg Ni/L, and 400 μg Ni/L) to determine the effects of salinity stress and supplemental nickel applications on nitrogen metabolism following foliar applications of urea nitrogen at 9.8 kg ha^-1 weekly. Parameters measured included: urease activity, total amino acid content, and tissue nutrient content.   Preliminary results indicate that urease levels were increased with supplemental levels of nickel.   Both 200 μg Ni/L and 400 μg Ni/L (supplied as NiCl₂) significantly increased urease levels within leaf tissue over the control treatment.  Secondly, ‘Diamond’ exhibited significantly higher urease levels than ‘TifEagle’.  These finding suggest that foliar applications of urea nitrogen could benefit from supplemental applications of nickel by stimulating urease activity leading to enhanced nitrogen metabolism.   Further observations will be made at the conclusion of the study.