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This thesis attempts to explain vertical market interaction within the food chain from a new perspective. It takes a two-stage game-theoretic framework from industrial organisation literature, and extrapolates this into the area of bargaining relationships. In turn, the inter-sectoral paradigm developed is applied to the specific area of agricultural marketing and the conventional wisdom of cooperatives is challenged. The resulting model allows new insights into such issues as countervailing market power, the dynamics of market structure and competition policy. Although the principles have been developed within the context of the U.K. food chain, they are of wider relevance. The conceptual framework developed underlines that in studying bargaining relationships and market structures the economic concept of equilibrium may be better replaced with a broader game-theoretic understanding of the market process.

The objective of this thesis was to gain more information about the post-harvest fungicide thiabendazole (TBZ), in terms of chemical residues in potatoes and in processed products and on factors affecting the storage quality of the crop. So that TBZ residues could be determined, a sensitive and accurate method for the extraction, clean-up and quantification of TBZ from potatoes, was derived. The recovery of the method was calculated at 93.8% 2.1%, and levels in the range of 0.004g TBZ could readily be detected. This method was then used to determine the distribution and penetration of TBZ in stored potatoes. The residue was found to associate with the skin of the potato, as its polarity hindered any further penetration of the chemical into the tuber. TBZ residue analysis was also carried out in processed potato products, including boiled potatoes, baked potatoes and crisps. As little work had been carried out in this area, these findings should provide the basis for future research, so that a complete picture can be built up with respect to residues in processed products. In general, cooking did not seem to affect either the chemical nature or the absolute residue value of TBZ in the product. The exception to this was the microwaved baked potatoes. In this sample, the residue had decreased after cooking. However, no decomposition products were detected and so the decrease in residue remains unaccounted for. Factors considered which affected the storage quality of the crop included i) the treatment of seed with TBZ to try to reduce the amount of chemical applied to the ware crop, while still maintaining the desired level of disease control, ii) the effect that TBZ and its formulations had on the wound healing capacity of potatoes and iii) the metabolism of TBZ by fungi and bacteria. The results of the seed treatment study were very disappointing. It was shown that a seed treatment of TBZ did not affect emergence or yield to any significant extent. The effects on disease control could not be studied satisfactorily though, because a particularly healthy crop was grown and no disease was in evidence (including the controls). The effect that TBZ had on wound healing was measured by following the development of resistance to water loss in cut potato discs. TBZ was found to promote the development of resistance to water loss in the early stages of wound healing, compared with the control, but after 21 days (the conclusion of each experiment) resistance to water loss was the same in TBZ treated discs, as in the controls. The initial increase in the development of resistance to water loss in TBZ treated discs may be sufficient to inhibit fungal and bacterial pathogens from entering the tubers. The formulation components of the TBZ also influenced the wound healing capacity of discs. Storite, a neutral suspension of TBZ, promoted wound healing to the same extent as TBZ in methanol. However, the acidic formulation of TBZ, Storite Clear, was found to inhibit wound healing and encourage bacterial rotting. The combined formulation of TBZ and 2-aminobutane, Storite Plus, had mixed effects and therefore no satisfactory conclusions could be made with respect to its effects on the wound healing process. TBZ was shown to have no significant, beneficial effects on curing in whole tubers. Therefore, although the chemical promotes wound healing, it does not necessarily follow that it will have the same beneficial effects on curing. It was important to study the metabolism of TBZ for three reasons:- i) to discover if loss of activity via metabolism was likely to be a problem, ii) to see if any metabolite formed was toxic and iii) to try to ascertain whether the development of resistance to TBZ was likely to become a problem. A number of fungal and bacterial cultures were set up, and resistant strains of the micro-organisms, if they developed, isolated. Of the micro-organisms subjected to TBZ, only soil bacteria, Erwinia carotovora, Phoma exigua and Phytopthora infestans developed resistance. From these isolates, P. exigua was the only micro-organism which metabolised TBZ. Very small amounts of TBZ (less than 0.08% of the TBZ initially administered) were metabolised to 5-hydroxy TBZ. These metabolism studies were carried out under optimum growing conditions for the bacteria and fungi, therefore the likelihood of P. exigua developing resistance to TBZ in a store is fairly low.

Pesticides are used worldwide and exhibit a plethora of different modes of action against a wide spectrum of organisms. Therefore, before they can be marketed they have to be tested against certain standardised regulations. These include the Food and Environment Protection Act 1985 (FEPA), the Control of Pesticides Regulations 1986 (COPR), and more recently the European Council Directive 1991 91/414 and the Plant Protection Products Regulations 1991 (PPPR). However, the current tests used to determine pesticide impacts on microorganisms as detailed by the OECD focus on only broadscale analytical methods that may mask more subtle effects that may still be ecologically significant. Therefore, this project aimed to determine the effects of a widely-used model pesticide, azoxystrobin on both target and non-target microbial communities across different trophic levels. The techniques used to perform this included broad- (soil microbial biomass and soil dehydrogenase activity) and fine-scale (T-RFLP, cloning/sequencing, and qPCR) analytical methods. The results of these analyses showed that the application of azoxystrobin had a significant, concentration-dependent impact on soil dehydrogenase activity whilst biomass was unaffected. The molecular analyses showed that azoxystrobin significantly impacted fungal community structure, diversity and gene copy number. Additionally, pesticide application significantly altered nematode community structure and general eukaryotic diversity. Soil and liquid culture enrichments showed that azoxystrobin degradation can be enhanced following repeated applications and enabled the isolation of two degrader organisms with sequence homologies to a Cupriavidus sp. and a Rhodanobacter sp. Further work showed that sequential enrichments with azoxystrobin also conferred cross-enhanced degradative abilities for three other strobilurin fungicides: pyraclostrobin, kresoxim methyl and trifloxystrobin. The work performed in this thesis served to illustrate how the current OECD test procedures may benefit from the incorporation of finer-scale molecular methods into its tests, as well as how difficult the task can be to produce compounds that persist in the environment long enough to perform their required function, but do not have significant deleterious impacts on non-target organisms when present.

Upland heather moorland is often subjected to wildfires, particularly in drought years, which destroy all vegetation, seed bank and surface peat. Post-fire management of liming, fertilising and seeding with grass species and Calluna vulgaris (ling heather), in addition to natural regeneration, often fails to fully re-vegetate the bare burnt peat, leading to erosion and degraded sites. Here, two sites were under investigation: Darwen Moor that suffered a severe fire in 1995, and a moor overlooking Stalybridge, Tameside, burnt in 1980. Both burnt areas received similar post-fire management. After a full vegetation survey of Darwen Moor, with data analysed using Two-way species indicator analysis (Twinspan), permanent quadrats were established within representative areas of identified vegetation sub-communities. Twice yearly surveys (spring and autumn) were undertaken within areas defined by these quadrats. Results of vegetation survey showed regeneration of C. vulgaris on burnt sections of Darwen moor had increased from 18% to 38%, (2000-2005), and had become the dominant species, with only 3% of the burnt moor remaining unvegetated. Vegetation succession was not advancing unidirectionally with increasing variation between samples of the same sub-community. This was in contrast to the Stalybridge site that remained unvegetated (77%) twenty-five years after wildfire. Survey data were collected using both digital photography and point quadrat survey. Pre-monitoring investigation showed no significant difference between data collected by these techniques. Experiments were undertaken to assess aspects of C. vulgaris seed dispersal and viability. Seed-trap experiments using transplanted C. vulgaris suggested that few seeds are being dispersed into degraded sites, whilst datalogger evidence showed poor germination opportunity for C. vulgaris seeds on moorland post-wildfire. C. vulgaris seeds were shown to germinate and grow on moorland peat in controlled conditions, although they rapidly became unviable when exposed to drought conditions. Use of a polyacrylamide gel to enhance environmental conditions for sown grass species showed early increased ground cover but failed to show any significant increase after 14 months. Accepted upland moorland revegetation management post-wildfire is reviewed and from experimental results, additional management techniques are suggested.

Firstly, increasing true stem RN capacity as means to increase the maximum rate of N uptake (kg N per day) during stem elongation may be feasible through optimisation of traits such as stem length and wall thickness. Secondly, modifying true stem RN unloading by increasing storage N in relation to accumulation N may offer a realistic mechanism for improving crop BPE and thus UTE. Such an increase in true stem NRE might be achieved through manipulation of key N assimilation enzymes. Thirdly, it may be possible to select for ‘stay-green’ traits associated with lower leaf lamina NRE and lower grain N% to boost UTE. However, in each case further phenotyping studies are required to characterise genetic variability, identify the most appropriate germplasm resources for genetic studies, and to identify appropriate genetic sources of variation for breeding.

Soil is one of the most complex ecosystems in the environment and changes to microbial diversity are thought to affect the physical structure (and vice versa). A fundamental question addressed in this research, is how microbial communities influence the functioning of soil, particularly with respect to the development and maintenance of a soil’s physical structure. Using micro- and macrocosms of sieved (and therefore structureless) soil, the effects of time, soil texture, manipulated background microbial diversity, and Plantago lanceolata (± mycorrhizal fungi) on the development of soil structure were determined. Background microbial diversity was manipulated using the dilution technique to give a low (101) dilution or a high (106) dilution of the original soil. This resulted in greater bacterial diversity in the lower (101) dilution than in the higher (106) dilution when in the presence of mycorrhizal plants. However, background diversity was the same irrespective of dilution in soils with non-mycorrhizal plants (and reversed within the bare soil). Micro- and macrocosms were continually assessed during controlled incubation periods ranging from 7 weeks to 15 months. Of the soil textures analysed (clay loam, loamy sand and sandy loam), loamy sand displayed the highest overall porosity as well as a noteworthy development in porosity throughout the incubation period. Mycorrhizal and nonmycorrhizal plants increased the speed of soil structural development by 5 months relative to unplanted soils. Although mycorrhizal fungi stunted root growth initially, aggregates within mycorrhizal planted treatments were smaller but nonetheless more stable than those in bare soil. Increasing mycorrhizal fungal species richness enhanced root and shoot biomass and reduced aggregate size and total porosity. There was a positive relationship between total porosity and numbers of culturable bacteria and fungi. In soils containing a lower microbial diversity, an increase in porosity, mean pore size, aggregate size and pore perimeter was observed. Results obtained were dependent on incubation conditions, planting regime and mycorrhizal status. Therefore, the effects of reducing microbial species diversity on soil structure parameters are idiosyncratic, with the presence of plant roots acting as a key factor.

A key aspect of the condition of soil as a medium for growing plants is the soil physical environment under which germination, growth and establishment occur. Crucially this affects factors such as water content, oxygen availability and soil strength. The dynamics of soil physical properties, and in particular soil structure, of a range of soils and how they relate to plant establishment are considered in this thesis. By engineering a variety of seedbeds and contrasting soil structures using different cultivation techniques, from intensive (plough) to reduced (disc) strategies, significant differences in the physical properties of the soils in terms of volumetric water content, soil strength and bulk density and interactions with plant establishment were identified. A model for Soil Quality of Establishment (SQE) was developed to predict plant establishment based upon soil bulk density and cultivation practices which significantly accounted for c. 50% of the variation occurring across contrasting soil types and environmental conditions. It was hypothesized from this that the precise porous architecture (i.e. soil structure) plays a crucial role in plant establishment given soil bulk density was a significant factor in the SQE model. Utilizing X-ray Computed Tomography (CT) both at a macro (c.300μm) and meso (c.65μm) scale soil structure (in terms of: porosity, pore area and perimeter, elongation, nearest neighbour distance, ECD and pore distribution) were determined in a quantitative manner. Results showed significant decreases in plant populations with associated increases in the soil porosity, with strong links to the pore size, roughness and spatial distribution (accounting for soil-seed contact, water storage / flow and ease of plant / root movement within the soil). Preferred porosity conditions for establishment and yield occurred between 12 - 20 % porosity (at the meso scale). SQE prediction was significantly improved with the addition of structural properties accounting for c. 70 % variation in crop establishment across soil texture and seasonal variation. The further 30 % variation in crop establishment may be explained by unforeseen circumstances such as disease and weather but equally this may also be related to crop genetics, soil chemistry and or the biological activities within the soil.