Mitigation and Current Management Attempts to Limit Pathogen Survival and Movement Within Farmed Grassland

Abstract

To successfully curb microbial contamination of surface waters we need to understand, and holistically evaluate, the range of mitigation strategies that have been designed to protect watercourses from non-point agricultural sources, so as to use them to best effect. A cost-effective and pragmatic approach is to improve knowledge of farm management operations capable of (i) reducing potential pathogen numbers in livestock manures and (ii) reducing subsequent transfer (through the environment) of fecal microorganisms derived from livestock manures that are recycled to land. This will prove important for supporting farmer decision making, devising policy and implementing mitigation practices to limit fecal microorganism delivery from land to water. In this chapter, we consider a diverse suite of manure, animal and land management options that range from simple manure composting techniques and the use of slurry additives, through to land mana gement engineering approaches and the design of constructed wetlands to protect watercourses from microbial contamination. The choice as to which strategy to use, if any, is ultimately made by the farmer and is likely to be influenced by a complex range of factors which may include, for example, tradition, convenience and farm economics. We conclude that the inherent complexity associated with heterogeneous landscapes confounds the likelihood that a single management strategy will provide complete protection of receiving waters from microbial contamination. Instead, the coupling of different strategies alongside improved education and considerable vigilance by farmers and landowners is needed for a more sustainable approach to limiting diffuse microbial (and, crucially, other contaminant) pollution from agriculture.

A cross-disciplinary toolkit to assess the risk of faecal indicator loss from grassland farm systems to surface waters

“…This toolkit attempts to prioritise targeting of mitigation efforts within source, transfer, infrastructure or management related areas. Consequently, mitigation does not necessarily only need to take the form of physical changes in infrastructure or landscape, but instead can be instigated through programmes of debt management or accreditation in training to complement more traditional mitigation approaches such as those outlined in Oliver et al (2007). Thus, the four axis approach suggests that, if a given farm had a large E. coli burden but the landscape features translated to minimal transfer potential then minimal risk would transpire.…”

Animal Waste, Water Quality and Human Health

“…As noted above, ponds provide ideal conditions for microbial attenuation. However, they can also be a source of infection where livestock and/or birds have access (Jones 2005, Oliver 2007. Since the 1970s, two-stage waste stabilisation ponds (WSPs), comprising an anaerobic pond (AP) and a facultative pond (FP), have been widely used to treat dirty water on dairy farms in New Zealand.…”

“…Kivaisi 2001, Song 2005, Vymazal 2006) and represent a sustainable, low-energy/maintenance form of treatment, particularly suited to rural areas (Kadlec & Knight 1996). Essentially, their design spectrum ranges from free water surface (FWS) systems that are either free of, or have different proportions of, emergent macrophytes (typically reeds) to subsurface flow (SSF) systems which act as a percolating filter, with wastewater being applied intermittently and seeping down through, or horizontally past, the plant rhizosphere and supporting media, such as gravel and sand (Oliver 2007). Components range from a simple pond to an engineered horizontal-flow reedbed.…”

Catchments, sub-catchments and private spaces: Scale and process in managing microbial pollution from source to sea

“…Yet if we were to investigate uptake of measures on a farm-byfarm basis then such assumptions are likely to be inconsistent with the ground-truthing of data simply because a diverse subset of socio-economic factors are likely to dictate farmer decision making and uptake at the local level. In turn, it becomes difficult to guarantee that within a catchment, neighbouring farms will not jeopardize microbial water quality at the expense of the effort of others (Oliver et al, 2007). We therefore need to know the spatial pattern of uptake but the catchment scale may be too coarse to represent these patterns in a meaningful way.…”