Submitted to: American Society for Microbiology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/21/2003
Publication Date: 5/20/2003
Citation: MILLER, D.N., BERRY, E.D. EFFECT OF MOISTURE AND MANURE CONTENT ON MICROBIAL PROCESSES IN CATTLE FEEDLOT SOILS: GREENHOUSE GASES, NUTRIENT LOSSES, AND ODORS. AMERICAN SOCIETY OF MICROBIOLOGY MEETING. 2003. Abstract p. 547. Interpretive Summary:
Technical Abstract: Microorganisms play a central role in environmental challenges facing animal agriculture. Aerobic and anaerobic processes in the manure affect greenhouse gas emissions, odors, and nutrient losses, but the controls on these processes are not well understood. Cattle feedlot surface moisture and manure content vary both spatially and temporally and are likely to be important controlling factors. This study examined the effect of six moistures (10% to 60%) and three manure/soil mixes (5%, 25%, and 75% manure) on greenhouse gases, nutrient losses, and odor compounds over a two-week period. Manure content most directly affected moisture-holding capacity in the manure mix, i.e., more moisture was needed to produce anaerobic conditions in the 75% manure mix compared to the 5% and 25% manure mixes. Moisture addition produced three conditions: no microbial activity at the lowest moistures, aerobic activity at moderate moistures, and anaerobic activity at the highest moistures. The primary greenhouse gas emitted from all but the driest soils was CO2 and was proportional to manure content. Minor trace gases (N2O and CH4) were also detected, but were important and comprised up to 98% of emitted CO2-equivalents. Urea hydrolysis to NH3 followed by its volatilization is a major route of nutrient loss from cattle feedlots. Urea in this study was rapidly converted to NH3, which was subsequently lost in all but the driest conditions. Odor compounds did not accumulate to high levels in any of the treatments. However, there were marked differences in the persistence of odor compounds originally present in the manure; odor compounds were rapidly lost under aerobic conditions, but persisted longer under anaerobic conditions. Anaerobic conditions also indirectly enhanced the volatility of odorous VFA due to acid accumulation. We conclude that moisture had the greatest effect on greenhouse gases, nutrient losses, and odor production. Manure content acted to modulate the effect of moisture.