TY - JOUR

T1 - Seasonal persistence of faecal indicator organisms in soil following dairy slurry application to land by surface broadcasting and shallow injection

AU - Hodgson, Christopher J.

AU - Oliver, David Michael

AU - Fish, Robert D.

AU - Bulmer, Nicholas M.

AU - Heathwaite, Ann Louise

AU - Winter, Michael

AU - Chadwick, David R.

PY - 2016/12/1

Y1 - 2016/12/1

N2 - 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.

AB - 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.

KW - Diffuse microbial pollution

KW - E. coli die-off

KW - Manure management

KW - Survival curves

KW - Organic fertiliser

KW - Pathogen risk

U2 - 10.1016/j.jenvman.2016.08.047

DO - 10.1016/j.jenvman.2016.08.047

M3 - Journal article

VL - 183

SP - 325

EP - 332

JO - Journal of Environmental Management

JF - Journal of Environmental Management

SN - 0301-4797

IS - Part 1

ER -