Bermudagrass Forage Yield and Ammonia Volatilization as Affected by Nitrogen Fertilization

Abstract

Forage fertilization practices are changing because of poultry litter use restrictions and reduced NH4NO3 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 NH3 volatilization. Four N sources, pelleted poultry litter (PPL), NH4NO3, 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 NH3 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 NH4NO3 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 NH4NO3 Cumulative NH3–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 NH4NO3 Given the limited availability of NH4NO3, restrictions on poultry litter use, and concerns about air quality, urea amended with NBPT is a suitable N source for bermudagrass.