Find in Library

Beef feedyards produce nitrous oxide (N₂O), a potent greenhouse gas. Limited research has evaluated the processes that produce feedyard N₂O, and how rainfall and temperature impact N₂O losses. Manure in feedyard pens develops into a complex ecosystem of microbes, extracellular enzymes, feces, and urine, with varying H₂O content. This study aimed to improve understanding of feedyard N cycling under differing environmental conditions by incubation of manure in simulated feedyard pens using large chambers under laboratory conditions. We hypothesized that nitrification was the primary source of feedyard N₂O, with interactions among temperature, H₂O content, and manure properties. Emissions of N₂O were monitored with a real–time N₂O analyzer. Manure samples were taken at intervals for analyses of physicochemical properties, denitrification enzyme activity (DEA), and nitrification activity (NA). Due to equipment limitations, there was only one chamber per temperature tested. Correlation was poor among N₂O emissions and rates of DEA and NA. However, significant relationships were found among key manure characteristics, such as ammonia/ammonium and nitrate/nitrite concentrations, manure dry matter, redox status, and temperature. These data suggest that most N₂O was derived from denitrification in the top 5 cm of the manure pack. Further study is warranted to identify the processes involved in flushes of N₂O emitted immediately after rainfall, possibly due to abiotic chemical reactions that release N₂O sequestered in manure pores.