ASA Southern Branch 2008 Annual Meeting
February 3-5, 2008
Dallas, TX

Monday, February 4, 2008 - 8:30 AM

Bermudagrass Forage Yield and Ammonia Volatilization as Affected by Nitrogen Fertilization.

Colin G. Massey, Nathan A. Slaton, Russell E. DeLong, Bobby L. Golden, Elliot T. Maschmann, and Trent L. Roberts. Crop, Soil, and Environmental Sciences, University of Arkansas, 1366 West Altheimer Drive, Fayetteville, AR 72704

Nutrient management for hay production is changing due to poultry litter use restrictions, decreased NH4NO3 availability, and increasing fertilizer costs which demand evaluation of fertilization strategies that maintain soil productivity and minimize N losses. Our research objectives were to i) compare yields of common bermudagrass [Cynodon dactylon] receiving a range of N rates from four N sources and ii) measure potential NH3-N losses. Experiments were conducted in 2006 and 2007 on a Captina silt loam. Pelleted poultry litter (PPL), NH4NO3, urea, and urea plus Agrotain (urease inhibitor) were applied at 0, 100, 200, 300, 400, and 500 kg N/ha/year in split applications. Ammonia volatilization was measured using a semi-closed chamber method in which NH3-N is trapped by sorbers that were changed 3, 6, 9, 12, and 15 d after fertilization. Bermudagrass receiving no N produced yields of 3,987 and 5,169 kg/ha in 2006 and 2007, respectively. In 2006, yields, averaged across N sources, increased as rate increased and were greatest (8600 kg/ha) with 500 kg N/ha/year. When averaged across rates yields were similar among inorganic-N fertilizers and 12% greater than forage receiving PPL. In 2007, the N rate by source interaction was significant showing a general trend for yields to i) increase as N rate increased and ii) vary among N sources in the order of NH4NO3 > urea = urea+Agrotain > PPL. Cumulative NH3-N losses by 15 d averaged 14% of applied N for urea, declined to 3% for urea+Agrotain, and were <1% of N applied as NH4NO3 and PPL. Urea produced similar to slightly lower forage yields as NH4NO3 and volatile losses of urea-N can be reduced by using Agrotain. Pelleted litter produced 87% of the yield as inorganic-N fertilizers and surprisingly had very low NH3 losses suggesting that pelletizing may enhance poultry litter’s N-fertilizer value.