2007 Annual Report 1a.Objectives (from AD-416) To determine, in cooperation with scientists from TAES, WTAMU, and TAMU, atmospheric ammonia concentrations and emissions at commercial beef cattle feedyards. Additionally, to determine the effects of environmental and management factors on ammonia concentrations and emissions. 1b.Approach (from AD-416) Ammonia emissions from three commercial beef cattle feedyards in Texas with differing management and nutritional regimens will be measured semi-continuously for approximately one year using open path lasers and a backlard Lagrangian stochastic model. Effects of environmental conditions on ammonia emissions will be determined. Nitrogen balance will be determined at the same feedyards based on chemical composition of rations, fresh feces, aged manure, and compost in order to support or refute the validity of the ammonia emissions obtained. These data can potentially serve as important components of a computer model to predict ammonia emissions from feedyards and to estimate the quantity and quality of manure removed from the feedyard. To study potential methods to decrease ammonia emissions from feedlot pen surfaces, a static chamber will be used in short intervals to measure the effects of pen surface treatments (urease inhibitors, alum, fat, zeolite, etc.) and environmental factors on ammonia emissions from urine spots. Ammonia emissions will be compared and correlated to chemical changes on the pen surface. 3.Progress Report This report serves to document research conducted under a reimbursable cooperative agreement between ARS and the Texas A&M University/Agricultural Experiment Station, College Station, Texas. Additional details of the research and publications can be found in the report for the parent project 6209-31630-002-00D, Minimizing the Environmental Impact of Livestock Manures Using Integrated Management Regimens. Ammonia sampling systems have been established at two commercial feedyards in the Texas Panhandle. The systems consist of open path ammonia lasers, weather stations, and sonic anemometers. Ammonia emissions are estimated using a backward Lagrangian stochastic model. Almost continuous data has been collected since October 2006. At monthly intervals samples of feed ingredients, pen surface manure, and fresh feces are collected and analyzed for dry matter, nitrogen, phosphorus, acid insoluble ash, pH and electrical conductivity in order to estimate nitrogen excretion and total nitrogen volatilization losses. Retention pond samples are also collected and analyzed for pH, temperature, and total ammonium nitrogen in order to estimate ammonia emissions from the retention pond using a mechanistic model. Tentative initial data agrees with data obtained from another feedyard, suggesting that on average 40 to 55% of nitrogen fed is subsequently lost as ammonia and that winter losses are about 50% of summer losses. The ADODR and TAES lead investigator are in regular contact via e-mail, phone, and face-to-face conversations.