Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/15/2011
Publication Date: 7/1/2011
Citation: McLaughlin, M.R., Brooks, J.P., Adeli, A., Tewolde, H. 2011. Nutrients and bacteria in common contiguous Mississippi soils with and without broiler litter fertilization. Journal of Environmental Quality. 40:1322-1331. Interpretive Summary: This study documented the amounts of selected nutrients, fecal bacteria and bacterial pathogens in soils after land applications of broiler litter in Mississippi. This is the first report to document levels of fecal and pathogenic bacteria in these litter-fertilized soils. The findings suggest that litter management plans in the state have been effective and appropriate. Levels of potential enteric bacterial pathogen, Listeria spp., did not differ from background levels found outside the litter-fertilized fields. Furthermore, the enteric pathogens, Campylobacter spp. and Salmonella spp., could not be cultured from any soil samples. We conclude from the present and earlier work that the enteric bacterial pathogen load transported to field soils during land application was relatively low, declined by natural die off and reached background levels. Results of the present study showed no evidence of cumulative buildup of enteric bacterial pathogens in litter-fertilized field soils. Risk assessment models for bacterial pathogen contamination from land application of litter have not been developed and although results found in the present study are encouraging, more research on temporal distribution of pathogens and new models are needed to fully assess potential risks.
Technical Abstract: In Mississippi, poultry litter is used to fertilize hay, pasture, small grain, and row crops. Levels of nutrients and bacteria in litter, and nutrients in litter-fertilized (L+) soil were known, but less was known of bacterial levels. This study examined contiguous L+ and non-litter-fertilized (L–) soils comprising 15 soil types. Soil surface cores (0-5 and 5-10 cm for bacterial tests and 0-15 cm for nutrient tests) were collected on five farms in Mar-May 2009. Soil pH, NO3--N, and both Mehlich-3-extractable (M3) and water-extractable (WE) P, Ca, K, and Cu were higher in L+ than L– soil. Total C, total N, NH4+-N, and both M3- and WE- Na, Fe, and Zn did not differ in L+ than L– soil. Bacteria levels were higher in 0-5 cm than in 5-10 cm cores. Levels were higher in L+ than L– soil for culturally determined heterotrophic plate counts and Staphylococcus spp., and lower for total bacteria estimated by quantitative PCR (qPCR) of 16S rDNA, but cultural levels of thermotolerant coliforms, Escherichia coli, Clostridium perfringens, and Enterococcus spp. were not different. Cultural presence/absence (PA) tests and qPCR for Listeria spp., Campylobacter spp., and Salmonella spp. detected only Listeria spp., which did not differ in L+ (PA=77% positive samples, mean qPCR = 0.65 log10 gu g-1) and L– (PA=70% positive samples, mean qPCR = 0 log10 gu g-1) soils. Higher pH, P, and Cu in L+ samples were consistent with litter applications, while levels of enteric bacterial pathogens did not differ. Litter did not affect pathogen loads in soils of this study.