Nutrient and Bacterial Levels in Common Contiguous Soils with and without Poultry Litter Fertilization.

In the Mid-South US, poultry litter is a valuable resource traditionally used to fertilize hay fields and pastures, but also used for small grains and row crops.  Levels of nutrients and bacteria in litter, and nutrients in litter-fertilized (LF) soil, are well documented, but less is known of litter bacterial levels in soil.  This study examined bacteria and nutrients in LF and non-LF (NLF) soils of the same soil types in adjacent formations.  Samples were collected Mar-May 2009 from soils spanning adjacent LF and NLF areas.  Paired cores for nutrient and bacterial tests, respectively, were collected within 10 cm of each other.  Cores were collected at 15-m intervals along transects in LF and NLF areas of each soil type.  Five nutrient cores (0-15 cm) and five bacterial cores (0-5 and 5-10 cm) were collected and combined, respectively, per sample.  Eight LF and eight NLF samples were collected on each of five farms.  Analyses across soils showed higher pH, NO₃^--N, Mehlich-3-extractable (M3) nutrients (P, Ca, K, and Cu), and water-extractable (WE) nutrients (P, Ca, Mg, K, Cu, and Mn) in LF than NLF soil, while total C, total N, NH₄⁺-N, M3-nutrients (Mg, Na, Fe, Mn, and Zn), and WE-nutrients (Na, Fe, and Zn) did not differ.  Bacterial levels were higher in LF than NLF soil for culturally determined heterotrophic plate counts and Staphylococcus spp., and for total bacteria estimated by quantitative PCR (qPCR) of 16S ribososomal DNA, but cultural levels of thermotolerant coliforms, Escherichia coli, Clostridium perfringens, and Enterococcus spp. were not different.  Cultural presence/absence (CPA) tests and qPCR for Listeria spp., Campylobacter spp., and Salmonella spp. detected only Listeria spp., which did not differ in LF (CPA=77% +samples, mean qPCR = 0.65 log₁₀ gu g^-1) and NLF (CPA=70% +samples, mean qPCR = 0 log₁₀ gu g^-1) soils.  Results indicate no differential incidence of Campylobacter spp., Listeria spp., or Salmonella spp. in LF soils.