Bermudagrass Forage Yield and Ammonia Volatilization as Affected by Nitrogen Fertilization

Forage fertilization practices are changing because of poultry litter use restrictions and reduced NH 4 NO 3 availability. Our objectives were to compare bermudagrass [ Cynodon dactylon (L.) Pers.] yield and N uptake among N sources and rates and evaluate the influence of N‐fertilizer source on NH 3 volatilization. Four N sources, pelleted poultry litter (PPL), NH 4 NO 3 , urea, and urea + N ‐(n‐butyl) thiophosphoric triamide (NBPT) were applied at rates of 0 to 500 kg N ha −1 yr −1 to common bermudagrass from 2006 to 2008. Measurements included dry matter yield and total N uptake from each N source applied at 400 kg N ha −1 yr −1 A semi‐open static chamber method was used to measure NH 3 volatilization for 15 d from each N source applied at 400 kg N ha −1 yr −1 in three split applications. Dry matter increased linearly in 2006 and curvilinearly in 2007 and 2008 as N rate increased, with maximum yields of 9910 to 14,328 kg ha −1 Forage fertilized with ≤300 kg PPL‐N ha −1 yr −1 produced 78 to 96% of the dry matter as the same rates of NH 4 NO 3 The addition of NBPT to urea showed no consistent benefit to yield or N uptake compared with urea alone. Urea‐based fertilizers produced similar to slightly lower yields and N uptakes than NH 4 NO 3 Cumulative NH 3 –N loss was greatest for urea (10.4–18.7% of applied N), intermediate for urea + NBPT (2.0–3.9%), and <1.5% for PPL and NH 4 NO 3 Given the limited availability of NH 4 NO 3 , restrictions on poultry litter use, and concerns about air quality, urea amended with NBPT is a suitable N source for bermudagrass.