Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/22/2004
Publication Date: 3/7/2005
Citation: Miller, D.N., Berry, E.D. 2005. Cattle feedlot soil moisture and manure content: I. Impacts on greenhouse gases, odor compounds, nitrogen losses, and dust. Journal of Environmental Quality. 34:644-655. Interpretive Summary: Feedlot surfaces experience a wide range of manure and moisture contents, which affect the emissions of odor compounds, NH3, greenhouse gases, and dust. Potential dust production was directly attributable to moisture and manure content, whereas other emissions were the product of, or affected by, microbial metabolism. The range of moisture and manure contents tested produced three general microbial metabolisms, no activity, aerobic activity, and fermentative activity. Microbial metabolism was fueled by glucose and starch and affected emissions by changing the pH, producing malodorous fermentation end products and greenhouse gases, and consuming free NH3. Minimizing environmentally important emissions requires understanding the context of emissions, the underlying mechanisms, and the relationships between emissions.
Technical Abstract: Beef cattle feedlots face serious environmental challenges associated with manure management, including greenhouse gas, odor, NH3, and dust emissions. Conditions affecting emissions are poorly characterized, but likely related to the variability of feedlot surface moisture and manure, which affect microbial processes. We examined the effect of six moisture (0.1 to 1.5 g H2O g-1 DM) and three manure contents (50, 250, and 750 g manure kg-1 total DM) on greenhouse gases, odor compounds, nitrogen losses, and dust potential from feedlot soils over a two-week period. Moisture addition produced three microbial conditions: no activity, aerobic, and anaerobic (fermentative) activity at low, moderate, and high moisture, respectively. Manure content acted to modulate the effect of moisture and enhance some microbial processes. Greenhouse gas (CO2, N2O, and CH4) emissions were dynamic at moderate to high moisture. Malodorous VFA compounds did not accumulate in any treatments, but their persistence and volatility varied depending upon acid accumulation (increased volatility) and aerobic metabolism (VFA loss). Starch was the dominant substrate fueling both aerobic and fermentative metabolism. Ammonia- and urea-N losses were observed in all treatments where microbial activity was observed, however, there was evidence for microbial nitrogen uptake. Finally, potential dust production was observed below defined moisture thresholds, which were related to manure matter content. Managing feedlot surface moisture within a narrow range (0.2 to 0.4 g H2O g-1 DM) and limiting manure content in the soil to <500 g organic matter kg-1 DM should minimize negative environmental effects.