Seasonal persistence of faecal indicator organisms in soil following dairy slurry application to land by surface broadcasting and shallow injection.
Dairy farming generates large volumes of liquid manure (slurry), which is ultimately recycled to agricultural land as a valuable source of plant nutrients. Different methods of slurry application to land exist; some spread the slurry to the sward surface whereas others deliver the slurry under the sward and into the soil, thus helping to reduce greenhouse gas (GHG) emissions from agriculture. The aim of this study was to investigate the impact of two slurry application methods (surface broadcast versus shallow injection) on the survival of faecal indicator organisms (FIOs) delivered via dairy slurry to replicated grassland plots across contrasting seasons. A significant increase in FIO persistence (measured by the half-life of E. coli and intestinal enterococci) was observed when slurry was applied to grassland via shallow injection, and FIO decay rates were significantly higher for FIOs applied to grassland in spring relative to summer and autumn. Significant differences in the behaviour of E. coli and intestinal enterococci over time were also observed, with E. coli half-lives influenced more strongly by season of application relative to the intestinal enterococci population. While shallow injection of slurry can reduce agricultural GHG emissions to air it can also prolong the persistence of FIOs in soil, potentially increasing the risk of their subsequent transfer to water. Awareness of (and evidence for) the potential for 'pollution-swapping' is critical in order to guard against unintended environmental impacts of agricultural management decisions.
Rothamsted Research, North Wyke, Okehampton, Devon, EX20 2SB, UK. Electronic address: chris.hodgson@rothamsted.ac.uk.
Christopher J
CJ
Hodgson
Biological & Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK.
David M
DM
Oliver
School of Anthropology & Conservation, University of Kent, Canterbury, Kent, CT2 7NR, UK.
Robert D
RD
Fish
Rothamsted Research, North Wyke, Okehampton, Devon, EX20 2SB, UK.
Nicholas M
NM
Bulmer
The Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK.
A Louise
AL
Heathwaite
Department of Politics, Amory Building, Rennes Drive, Exeter, Devon EX4 4RJ, UK.
Michael
M
Winter
School of Environment, Natural Resources and Geography, Bangor University, Bangor, Gwynedd, LL57 2UW, UK.
David R
DR
Chadwick
D000818:Animals; D003611:Dairy Products / Q000032:analysis* / Q000382:microbiology; D003612:Dairying / Q000379:methods*; D016983:Enterococcus / Q000302:isolation & purification; D004784:Environmental Monitoring / Q000379:methods; D004787:Environmental Pollution / Q000032:analysis; D004926:Escherichia coli / Q000302:isolation & purification; D005243:Feces / Q000737:chemistry* / Q000382:microbiology*; D065948:Grassland; D006207:Half-Life; D008372:Manure / Q000032:analysis / Q000382:microbiology; D012621:Seasons; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
D008372:Manure; D012987:Soil
Diffuse microbial pollution; E. coli die-off; Manure management; Organic fertiliser; Pathogen risk; Survival curves