Chris J. Hodgson

Spatial organization of the glucosinolate–myrosinase system in brassica specialist aphids is similar to that of the host plant

Secondary metabolites are important in plant defence against pests and diseases. Similarly, insects can use plant secondary metabolites in defence and, in some cases, synthesize their own products. The paper describes how two specialist brassica feeders, Brevicoryne brassicae (cabbage aphid) and Lipaphis erysimi (turnip aphid) can sequester glucosinolates (thioglucosides) from their host plants, yet avoid the generation of toxic degradation products by compartmentalizing myrosinase (thioglucosidase) into crystalline microbodies. We propose that death, or damage, to the insect by predators or disease causes disruption of compartmentalized myrosinase, which results in the release of isothiocyanate that acts as a synergist for the alarm pheromone E–β–farnesene.

Valuing local knowledge as a source of expert data: Farmer engagement and the design of decision support systems

Engagement with farmers and landowners is often undertaken by the research community to obtain information relating to typical land, livestock and enterprise management and generally centres on responses to questionnaire surveys. Farmers and land managers are constituted as expert observers of ground-level processes and provide diverse information on farming practices, enterprise economics and underpinning attitudes towards risk. Research projects designed to inform policy and practice may rely on such data to understand better on-the-ground decisions that can impact on environmental quality and the rural economy. Such approaches to eliciting local-level expert knowledge can generate large quantities of data from which to formulate rules relating to farm enterprise types. In turn, this can help to inform the structure of Decision Support Systems (DSS) and risk-based tools to determine farming practices likely to impact on environmental quality. However, in this paper we advocate the need for integrated farmer participation throughout the whole research process - from project inception through to community qualitative validation and legitimation - and thus not just for the elicitation of questionnaire responses. With farm questionnaire surveys being adopted widely by the research community, it is an opportune time to highlight a recent case study of the Taw catchment, Devon, UK. This serves as an example of co-construction of a DSS via a co-ordinated and integrated approach to expert elicitation with a farmer questionnaire survey as a central methodology. The aim of the paper is to detail the core aspects of an iterative cycle of participatory environmental management and DSS development for water quality protection and consider the multiple benefits of co-ordinated programmes of engagement with the farming community in this process.

Interactions among agricultural production and other ecosystem services delivered from European temperate grassland systems.

Global demand for food is increasing as is the recognition that this must be achieved with minimal negative impacts on the environment or other ecosystem services (ESs). Here we develop an understanding of the relationships among ESs delivered within temperate agricultural grassland systems in lowland Europe. We reviewed the refereed literature on pair-wise interactions between nine different ESs. These were agricultural production, climate regulation, air quality regulation, water quality regulation, hydrological regulation, soil erosion regulation, nutrient cycling, biodiversity conservation, and landscape quality. For each pair, we sought information on how each ES responds to changes in the other. Each interaction was assigned to one of five categories: (i) no direct relationship between the driving ES on the responding ES, (ii) the driving ES has a negative impact on the responding ES, (iii) the driving ES has a positive impact on the responding ES, (iv) the evidence of direction of effect is inconclusive, because of either inadequate information or contradictions in the literature, and (v) there is no current evidence in the current literature for a relationship. Negative relationships resulted only from the effects of increasing the intensity of agricultural production on other ESs. Available evidence infers that erosion regulation and good nutrient cycling were the only two driving ESs shown to enhance agricultural production implying that their protection will enhance our ability to meet future food needs. In order for agriculture to become more sustainable, we need to develop agricultural methods that can minimize the negative impacts of these win–lose relationships.

Scale appropriate modelling of diffuse microbial pollution from agriculture

The prediction of microbial concentrations and loads in receiving waters is a key requirement for informing policy decisions in order to safeguard human health. However, modelling the fate and transfer dynamics of faecally derived microorganisms at different spatial scales poses a considerable challenge to the research and policy community. The objective of this paper is to critically evaluate the complexities and associated uncertainties attributed to the development of models for assessing agriculturally derived microbial pollution of watercourses. A series of key issues with respect to scale appropriate modelling of diffuse microbial pollution from agriculture is presented, and these include: (1) appreciating inadequacies in baseline sampling to underpin model development; (2) uncertainty in the magnitudes of microbial pollutants attributed to different faecal sources; (3) continued development of the empirical evidence base in line with other agricultural pollutants; (4) acknowledging the value of interdisciplinary working; and (5) beginning to account for economics in model development. It is argued that uncertainty in model predictions produces a space for meaningful scrutiny of the nature of evidence and assumptions underpinning model applications around which pathways towards more effective model development may ultimately emerge.

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

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 micro-organisms 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 micro-organism 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 management 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 land-owners is needed for a more sustainable approach to limiting diffuse microbial (and, crucially, other contaminant) pollution from agriculture.

Establishing relative release kinetics of faecal indicator organisms from different faecal matrices

Aims:  A laboratory assay for comparative characterization of various faecal matrices with respect to faecal indicator organism (FIO) release using, artificial rain water.

Development and testing of a risk indexing framework to determine field-scale critical source areas of faecal bacteria on grassland

This paper draws on lessons from a UK case study in the management of diffuse microbial pollution from grassland farm systems in the Taw catchment, southwest England. We report on the development and preliminary testing of a field-scale faecal indicator organism risk indexing tool (FIORIT). This tool aims to prioritise those fields most vulnerable in terms of their risk of contributing FIOs to water. FIORIT risk indices were related to recorded microbial water quality parameters (faecal coliforms [FC] and intestinal enterococci [IE]) to provide a concurrent on-farm evaluation of the tool. There was a significant upward trend in Log[FC] and Log[IE] values with FIORIT risk score classification (r^2 = 0.87 and 0.70, respectively and P < 0.01 for both FIOs). The FIORIT was then applied to 162 representative grassland fields through different seasons for ten farms in the case study catchment to determine the distribution of on-farm spatial and temporal risk. The high risk fields made up only a small proportion (1%, 2%, 2% and 3% for winter, spring, summer and autumn, respectively) of the total number of fields assessed (and less than 10% of the total area), but the likelihood of the hydrological connection of high FIO source areas to receiving watercourses makes them a priority for mitigation efforts. The FIORIT provides a preliminary and evolving mechanism through which we can combine risk assessment with risk communication to end-users and provides a framework for prioritising future empirical research. Continued testing of FIORIT across different geographical areas under both low and high flow conditions is now needed to initiate its long-term development into a robust indexing tool.

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.

The stable oxygen isotope ratio of resin extractable phosphate derived from fresh cattle faeces.

Rationale Phosphorus losses from agriculture pose an environmental threat to watercourses. A new approach using the stable oxygen isotope ratio of oxygen in phosphate (δ18OPO4 value) may help elucidate some phosphorus sources and cycling. Accurately determined and isotopically distinct source values are essential for this process. The δ18OPO4 values of animal wastes have, up to now, received little attention. Methods Phosphate (PO4) was extracted from cattle faeces using anion resins and the contribution of microbial PO4 was assessed. The δ18OPO4 value of the extracted PO4 was measured by precipitating silver phosphate and subsequent analysis on a thermal conversion elemental analyser at 1400°C, with the resultant carbon monoxide being mixed with a helium carrier gas passed through a gas chromatography (GC) column into a mass spectrometer. Faecal water oxygen isotope ratios (δ18OH2O values) were determined on a dual‐inlet mass spectrometer through a process of headspace carbon dioxide equilibration with water samples. Results Microbiological results indicated that much of the extracted PO4 was not derived directly from the gut fauna lysed during the extraction of PO4 from the faeces. Assuming that the faecal δ18OH2O values represented cattle body water, the predicted pyrophosphatase equilibrium δ18OPO4 (Eδ18OPO4) values ranged between +17.9 and +19.9‰, while using groundwater δ18OH2O values gave a range of +13.1 to +14.0‰. The faecal δ18OPO4 values ranged between +13.2 and +15.3‰. Conclusions The fresh faecal δ18OPO4 values were equivalent to those reported elsewhere for agricultural animal slurry. However, they were different from the Eδ18OPO4 value calculated from the faecal δ18OH2O value. Our results indicate that slurry PO4 is, in the main, derived from animal faeces although an explanation for the observed value range could not be determined.