Monday, November 13, 2006

Ammonia and Nitrous Oxide Emissions from Surface Applied Poultry Litter under Conservation Tillage Management Practices.

Glenn Johnson1, Harry Schomberg2, Dinku Endale2, and Mike Jenkins2. (1) Mother Earth Agronomy Inc., 2623 2nd Ave., Scottsbluff, NE 69361, (2) USDA-ARS, 1420 Experiment Stn Rd., Watkinsville, GA 30677

 SEQ CHAPTER \h \r 1Land application of poultry litter provides essential nutrients for crop production, but nitrogen (N) losses to the atmosphere can be detrimental to the environment.  A multi-season study was conducted to quantify ammonia (NH3) and nitrous oxide (N2O) volatilization rates from surface applied poultry litter under no-till (NT) and paraplowed (PP) conservation tillage managements.  Litter was applied in the winter and summer at rates of  100 and 200 kg N ha-1, respectively.  Evaluation of volatilization rates were determined using gas concentrations and the flux-gradient gas transport technique and the momentum balance transport coefficient.  Nitrous oxide fluxes ranged from 4.4 to 7.6% of total N applied.  Total N2O losses were about 22% larger during the summer than winter study but a larger percentage of applied N was lost during the winter.  Nitrous oxide losses during the winter were 8.1 and 7.2 kg ha-1 for the NT and PP treatments, respectively.  Total losses during the summer were 11.2 and 7.4 kg N2O ha-1 for the NT and PP treatments, respectively.  The relatively large losses during the winter indicate the importance of year-round measurements for accurate N2O emission estimates.  The losses found in this study were substantially greater than the 1.25% emission factor used by the Intergovernmental Panel on Climate Change to estimate global emissions and may have been related to the reduced tillage management practices used in these studies.  Ammonia fluxes ranged from 3.3 to 24% of the total N applied during the winter and summer, respectively.  Ammonia  volatilization was rapid immediately after litter application and stopped within 7 to 8 days.  Precipitation of 17 mm essentially halted volatilization, probably by transporting litter N into the soil matrix.  There was no differences in total NH3 volatilization between no-till and paraplowed treatments.