2009 Annual Report
1a.Objectives (from AD-416)
Our overall goals are 1. to understand better the survival kinetics and hydrologic transport characteristics of manure pathogens and their associated fecal indicator bacteria in agricultural watersheds, and 2. to improve our understanding of the emissions of ammonia and greenhouse gases from manures and manure applications. To accomplish goal 1., we propose three interrelated objectives: A) develop a method detection limit for Salmonella in environmental soil, poultry litter, and water samples with quantitative, real-time polymerase chain reaction (qPCR); B) determine inactivation or die off rates of Salmonella and the fecal indicator bacteria Escherichia coli and fecal Enterococcus spp. In field soils under controlled and field conditions; and C: determine the hydrologic transport characteristics of manure pathogens and fecal indicator bacteria at the field plot and small zero-order watershed scales. To accomplish goal 2., we propose to pursue the following two objectives: D) to measure ammonia and global-change trace gas emissions from land application of poultry litter under different tillage management, and E) from wetlands receiving nitrogen inputs from pastures.
1b.Approach (from AD-416)
Goal 1.: A real-time, quantitative polymerase chain reaction (qPCR) method will be developed to quantity the concentrations of Salmonella in poultry litter, and in environmental soil and water samples exposed to field applied poultry litter. With sentinel chambers, the aforementioned qPCR method, and defined cultural methods inactivation rates of Salmonella, and fecal indicator bacteria in agricultural soils will be determined under laboratory and field conditions. In collaboration with the Poultry Microbiological Safety Unit at the Russell Research Center, Athens,GA, and Southeast Watershed Research Laboratory, Tifton, GA overland transport of manure pathogens and fecal indicator bacteria from field applied poultry litter will be characterized at the field-plot level under various slope and aspect and under conditions of simulated rain, and at the small watershed-scale level that will depend on natural weather conditions. Goal 2.: Soil chambers will be used to measure gaseous emissions from poultry litter after soil application. Emissions will be evaluated under different tillage management systems. Small riparian/wetland areas will be studied to determine the proportion of hydrologic input nitrogen is transformed into gaseous nitrogenous emissions.
Recently published methods that combine culture-based most probable number methodology with a real-time polymerase chain reaction (PCR) confirmation step for enumerating Salmonella and E. coli 0157:H7 in environmental water and soil samples have superseded the non-culture-based real-time, quantitative PCR method originally proposed for this project. These two methods have reestablished a limit of detection for Salmonella and E. coli 0157:H7 in environmental water. With modifications of these new methods of enumerating Salmonella and E. coli 0157:H7 combined with sentinel chamber technology experiments, we have compared the die-off rates of the pathogen E. coli 0157:H7 with die-off rates of fecal indicator bacteria, generic E. coli and fecal enterococci. In anticipation of rain events with runoff, loads of fecal of indicator bacteria have been determined for the four cropped and instrumented watersheds that receive poultry litter and periodic cattle grazing.
The thirteen million metric tons of poultry litter that is produced annually in the U.S. has become a public health concern. One particular concern is that poultry litter contains the reproductive hormones estradiol and testosterone. These are endocrine disruptors that have been detected in surface waters worldwide. The objective of this study was to evaluate the potential impact of poultry litter applications on estradiol and testosterone concentrations in subsurface drainage and surface runoff in irrigated crop land under no-till and conventional-till management. Results of two irrigation studies, one in fall and one in spring, demonstrated that concentrations of the two hormones measured in drainage, runoff, and soil from litter applications did not add to background concentrations of either hormone. Significant differences were, however, observed between tillage management practices: concentrations of estradiol were greater for no-till than conventional-till management for the spring irrigation; but total quantities of both estradiol and testosterone in runoff were less from no-till than conventional-till fields for the fall irrigation. The differences between no-till and conventional-tillage appeared to be related to variation in hydrologic transport for the two tillage systems. Although differences were observed between tillage practices, the application of poultry litter at rates set by the nutritional requirements of the crop appears to have little potential of contaminating surface and subsurface waters with these hormones. This is important information for the poultry industry and environmental protection agencies because surface waters contaminated with hormones from poultry litter are likely an indication of inappropriate or mismanagement of litter applications.
Fecal contamination of recreational, drinking and fishing waters is a major global problem. Detecting and ranking the sources of fecal pollution is challenging as common methods used cannot discriminate among the sources. Microbial source tracking (MST) tested in this project utilized four genetic markers specific for ruminants to identify the animal source and origin of fecal pollution. Identifying sources of fecal contamination is important because it is the first step in stopping the source. This project investigated two watersheds with different management histories. In the watershed impacted by cattle the four genetic markers specific for cattle were detected in 32 to 65% of the DNA extracted from water and sediment samples. In contrast, at the site not impacted directly by cattle, in only 6% of the water samples assayed were the genetic markers detected. The detection of the genetic markers was correlated to the abundance of the fecal indicator bacteria fecal enterococci. This emerging MST approach removes subjectivity, and offers potential for identifying, tracking, and characterizing fecal sources and reservoirs and provide a tool for remediation and enforcement.
Watersheds with animal agriculture have the potential to adversely impact recreational waters and threaten public health by contaminating surface waters with fecal pathogens such as E. coli 0157:H7. To understand and manage the fate and transport of E. coli 0157:H7 in agricultural watersheds we developed a method of detecting and quantifying dilute concentrations of E. coli 0157:H7 in environmental surface waters. This method has determined the concentration of E. coli 0157:H7 in 20-liter samples taken from the inflow and outflow streams of a pond in an agricultural watershed as low as 0.1 E. coli 0157:H7 cells/liter and identified substantial fluxes of E. coli 0157:H7 when the fecal indicator bacterium E. coli was not detected. The sensitivity of this method will improve our understanding of the fate and transport of E. coli 0157:H7 in agricultural watersheds. The methodology will enhance our ability to assess this pathogen’s risk to public health and be helpful in identifying the actual sources of this pathogen because this method offers the potential for developing culture collections of E. coli 0157:H7.
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Jenkins, M., Endale, D.M., Schomberg, H.H., Hartel, P., Cabrera, M. 2009. 17B-Estradiol and testosterone in drainage and runoff from poultry litter applications to tilled and no-till crop land under irrigation. Journal of Environmental Management. 90:2659-2664.
Lee, Y., Marirosa, M., Santo Domingo, J.W., Cyterski, M., Endale, D.M., Shanks, O.C. 2008. A temporal assessment of cattle fecal pollution in the watersheds using 16S rRNA gene-based and metagenome-based assays. Applied and Environmental Microbiology. CDROM.