|Line, John - Eric|
|Franklin, Dorcas - Dory|
Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2008
Publication Date: 7/29/2008
Citation: Jenkins, M., Truman, C.C., Siragusa, G.R., Line, J.E., Bailey, J.S., Frye, J.G., Endale, D.M., Franklin, D.H., Schomberg, H.H., Fisher, D.S., Sharpe, R.R. 2008. Rainfall and tillage effects on transport of fecal bacteria and sex hormones 17ß-estradiol and testosterone from broiler litter applications to a Georgia Piedmont Ultisol. Science of the Total Environment. 403(1-3):154-163.
Interpretive Summary: The poultry industry generates millions of tons of poultry litter annually. A major fraction of this litter is applied to pastures and cropped fields as fertilizer. Fecal bacteria, and the potent gender regulating hormones, estradiol and testosterone, are natural components of litter. In addition, sub-therapeutic levels of antibiotics are added to chicken feed and antibiotic residues can also be in poultry litter. Scientists, policy-makers, and the poultry industry require information to determine if these components of litter pose a risk to public health when litter is applied to agricultural fields. Scientists at the USDA-ARS J. Phil Campbell Sr. Natural Resource Conservation Center in Watkinsville, GA, USDA-ARS Southeast Watershed Research, Tifton, GA, and USDA-ARS Russell Research Center, Athens, GA performed two controlled rainfall simulations on long-term no-till and conventional tillage fields to determine whether fecal bacteria (E. coli, Salmonella, Campylobacter, and Clostridium perfringens), sex hormones, and antibiotic residues were transported with runoff from rainfall simulations, and whether tillage practice had an effect on how much of these potential contaminants. Two kinds of rainfall simulations were undertaken; one at a constant intensity, and another at a variable intensity that mimicked a storm event. The scientists found that more runoff resulted from the variable simulation, and attributed this increase to the peak rainfall intensity that was substantially greater than the intensity of the constant simulation. In both cases, runoff volumes were greater for the conventionally tilled plots than the no-till plots. They did not detect Salmonella, Campylobacter, or antibiotic residues in any litter, soil, or runoff samples. They observed that the litter application enhanced the soil E. coli population, and testosterone runoff concentrations above background levels. The concentrations of testosterone, however, were not so great above its detection limit to warrant a concern. Otherwise the poultry litter application at rates commensurate for corn production did not enhance levels of other fecal bacteria, or the hormone estradiol above background. The scientists cautioned, however, that other researchers have reported higher levels of sex hormones in litter than found in the litter used in this study. They, therefore, cannot conclusively say that applying litter at agronomic rates will not increase estradiol and testosterone in the environment such that they become an environmental concern. The scientists recommended that further research is needed to determine the range of hormone concentrations likely to be found in litter and to identify management practices that minimize hormones that may be released to the environment. This information can be used by the poultry industry and environmental agencies to ensure safe application of the million of tons of poultry litter generated annually in the USA.
Technical Abstract: Poultry litter provides plant nutrients for crop and pasture production. Fecal bacteria, sex hormones (17ß-estradiol and testosterone) and antibiotic residues are litter components, however, that may contaminate surface waters and become a public health risk. Our objective was to quantify transport of fecal bacteria, estradiol, testosterone and antibiotic residues from a Cecil sandy loam under long-term no-till (NT) and conventional tillage (CT) to which either poultry litter (PL) or conventional fertilizer (CF) was applied based on the nitrogen needs of corn (Zea mays L) in the Southern Piedmont of NE Georgia. Each 2 by 3-m simulation plot within each of three replicated plots received one hour of simulated rainfall either at a constant rate of 55 mm h-1 in spring of 2004, or variable rainfall intensity in spring of 2005 for a total of 55 mm. Soil was sampled before and after rainfall simulation. Neither Salmonella, nor Campylobacter, nor antimicrobial residues were detected in litter, soil, or runoff samples. Differences in soil concentrations of fecal bacteria before and after rainfall simulations were observed only for Escherichia coli in the Ic experiment. Differences in flow-weighted concentrations were observed only for testosterone in both constant intensity and variable intensity rainfall experiments and were greatest for treatments that received poultry litter regardless of tillage system. In contrast to flow-weighted concentrations, total loads of E. coli, fecal enterococci, and testosterone were largest for the conventional tillage treatments receiving poultry litter indicating the effect of total runoff volume as a factor in total loads of microbial and hormonal contaminants. Poultry litter application rates commensurate for corn appeared to enhance only soil concentrations of E. coli, and runoff concentrations of testosterone above background levels but these effects do not appear to be a threat to public health.