Die-off of Escherichia coli in intact and disrupted cowpats

摘要

Diffuse pollution from grazed pastures is recognised as an important source of faecal microbial contamination of surface waters, and farmers urgently require mitigation options to reduce this impact of their farming activities. An obvious mitigation strategy is to reduce the size of the reservoir of faecal material in pastures during critical periods when overland flow is most likely. This work tested the hypothesis that smearing fresh cowpats to increase their surface area would increase exposure to solar radiation and increase desiccation, which in turn would accelerate the die-off of Escherichia coli in the faecal material. The total solids content and E. coli concentration in intact and disrupted cowpats were monitored during the four seasons. The total solids content was significantly (P < 0.001) higher in the disrupted cowpats compared to the intact cowpats. This indicates that increased desiccation of the faecal material was successful. However, there was no significant difference (P > 0.05) in E. coli concentrations in the disrupted and intact cowpats. The physical disruption of cowpats did not therefore accelerate the die-off of E. coli in the faecal material. The disrupted cowpats did appear to decompose faster than the intact cowpats. Mitigation options to reduce faecal micro-organism losses in overland flow from grazed pastures will now need to focus on other methods to reduce the build up of reservoirs of faecal material on farm.