2008 Joint Annual Meeting (5-9 Oct. 2008): The Effect of New Nitrogen Fertilizer Formulations on the Yield and Nitrogen Use Efficiency of Bermudagrass.

Several new nitrogen fertilizer formulations have been developed to increase nitrogen use efficiency (NUE) and reduce potential environmental losses. The objectives of this research were to compare the yields and N recovery in bermudagrass hay of Environmentally Smart Nitrogen^® (ESN) or Nutrisphere-N™ (NSN) treated urea to conventional applications of urea and ammonium nitrate (AN).  Plots (2.1 x 3.7 m) were delineated within a previously established stand of bermudagrass (cv. ‘Russell’) at UGA Agricultural Experiment Station facilities near Calhoun and Eatonton, GA. Soil types were a silt loam and loam, respectively. The experiment was a randomized complete block design with four replicates. The 17 treatment combinations included two rates (168 or 336 kg actual N ha^-1 yr^-1) of ESN, NSN, or urea applied once or twice during the season; urea or AN split equally across regrowth periods; and a 0 N control. Rainfall during the growing season (Mar-Sept) was at historic lows during 2007 (353 and 511 mm at Calhoun and Eatonton, respectively) and resulted in merely 1/3 of normal seasonal yield totals. At both locations, there was a significant cutting date x treatment interaction. During the extremely dry first growth period, yields of the ESN treatments (512 kg DM ha^-1) were significantly less than NSN, urea, and AN treatments (1255 kg DM ha^-1), but not the check plots (570 kg DM ha^-1). However, N formulation did not have a consistently significant effect on yield in subsequent harvests In Calhoun, N application rate significantly affected NUE (57.5 and 35.4 kg DM kg actual N ha^-1 yr^-1 for 168 or 336 kg actual N ha^-1 yr^-1, respectively). However, NUE was not affected by treatments in Eatonton. Additional research is needed during normal and wet years to assess the effect of N fertilizer formulation, rate, and timing on yield and NUE in bermudagrass.