Abstract
Agricultural intensification can lead to high volumes of livestock faeces being applied to land, either as solid or liquid manures or via direct defecation, and can result in reservoirs of faecal indicator organisms (FIOs) persisting within farmland. Understanding the survival of FIOs, e.g. E. coli, in agricultural environments, and in particular within different livestock faeces, is key to developing catchment management practices for the protection of ecosystem services provided by clean water. Frequently, controlled laboratory studies, under constant temperature regimes, are used to determine the impact of environmental factors on E. coli persistence in livestock faeces; however, such studies oversimplify the diurnal variations and interactions of real world conditions. The aim of this study was to investigate the survival of E. coli using a controlled environment facility, which simulated diurnal variation of temperatures typically experienced during a British spring and summer. The approach provided a comparison of E. coli persistence profiles within faeces of sheep, beef cattle and dairy cattle to allow novel interpretations of E. coli regrowth patterns in contrasting livestock faeces in the period immediately post-defecation. Thus, the coupling of a tightly controlled environment facility with high resolution monitoring enabled the development of a new non-linear, asymptotic description of E. coli proliferation in livestock faeces, with increased potential for E. coli growth observed during warmer temperatures for all livestock types. While this study focused on temperatures typical of the UK, the occurrence of a phase of E. coli regrowth has implications for microbial water quality management worldwide.
Highlights
Increased demand for food production has led to approaches that aim to deliver sustainable intensification in agricultural systems (Rockström et al, 2017)
A linear approach to modelling faecal indicator organisms (FIOs) survival is likely to underestimate the burden of E. coli in fresh livestock deposits because it does not account for E. coli proliferation, under favourable conditions, as observed in field studies, and captured within a controlled environment facility (CEF) mimicking fluctuating environmental conditions
The model developed as part of the current study provides a critical preliminary step towards a framework of accounting for seasonal variations in E. coli growth associated with livestock faeces at the catchment scale
Summary
Increased demand for food production has led to approaches that aim to deliver sustainable intensification in agricultural systems (Rockström et al, 2017). Despite best efforts to promote sustainable intensification, the need to feed a growing population can still lead to poor management of livestock, and the unsustainable use of agricultural land and (in)organic fertilisers, with the potential to impact negatively on wider environmental quality (Yang et al, 2016). Increased livestock numbers on-farm could lead to higher volumes of livestock faeces being applied to land, either as manure, slurry or via direct defecation, introducing large quantities of faecal indicator organisms (FIOs) to agricultural landscapes. A important source of E. coli in agricultural landscapes is freshly excreted livestock faeces which, unlike most slurry and farmyard manure, does not undergo any storage or treatment prior to land application and often contains a higher concentration of FIOs (Vinten et al, 2004)
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