Crude extracts of the seed kernels of the neem tree (Azadirachta indica) are widely used as plant protection products. The active ingredient (a.i.) of these extracts is azadirachtin A (aza A). aza A is a phytochemical (botanical) complex secondary metabolite which, with it is multiple toxic effects on insects, protects the plant against predation. Aza A is present in only low concentration in neem oil, but makes up 20-50% in the NSKEs extracted by polar solvents from the kernels. However, when used as foliar sprays it is rapidly destroyed by sunlight, and might be more effective if it is used systemically. Therefore the aim of the project was to extend previous work and to prepare a pelleted version of the main commercially-available neem-seed kernel extract, NeemAzal®-Technical (NAT) produced by Trifolio GmbH, in preparation for the expected registration of the product in the UK in 2011. It was first necessary to purify a quantity of aza A for quantification of the a.i. pelleted material and in soil and plants in the rest of the project. In achieving high purity (over 98%) aza A, reverse phase chromatographic methods were used, and mass spectrometery was used to confirm purity and identification. A final quantity of 6.2 mg of azadirachtin A was obtained from 4 gm of NAT, a yield of 0.15%. If aza A and the other neem terpenoids are to be used to plant protection, they must have a low phytotoxicity. Effect of NAT on the germination and its ensuing seedling development of two commercially important crops, sugar beet and cabbage was examined. NAT did have an inhibitory effect on seedling growth at 10-3 M aza A. In order to explore the inhibitory affect of aza A, the second part of the chapter was to examine effect of aza A on mitosis of onion root tips. The limonoids in concentration of 10-3 M adversely affected the mitotic activity of onion root tip cells. This could be failure of microtubules polymerisation into microtubules, or some other biochemical effect. From the findings in this part of the project, it can be concluded that only at a concentration of 10-3 M is aza A toxic to plant young seedlings, but in practice this is unlikely to be a significant problem. The first part of Chapter 4 of the project was to lay the foundations for the behaviour of aza A in soil environment in both powder form and in 2 types of granular formulations. The half-life of azadirachtin in soil from this work was found to be 1.6 days which is consistent with the previous reports. This short half-life of aza A may be problematic in use as a PPP. The short persistence might be overcome by formulating neem materials in granules to achieve environmental stability and biological efficacy of application. The granular formulations used in the project showed controlled release characteristics. The release of azadirachtin into the soil water was in fact delayed by encapsulating it in pellets. Systemic uptake of aza A by roots and subsequent presence in the vascular system of plants was assessed. Aza A was transported and was more stable in the leaf areas of cabbage and sugar beet plants than in the soil, as the half-life was found to be 9 days. The concentration of aza A in the leaf-water was less than 10% of the solution bathing the roots. The final part of the project, the application of the pelleted NSKE to protect cabbage, in both glass house and field conditions, demonstrated that neem products in pelleted formulations could be used as effective, systemically applied PPP to control pests of cabbage. In the field tests, the protective effect of the neem extract could be shown over a period of at least 5 weeks after addition of the pellets to the soil. In conclusion, the short soil half-life of the neem a.i., aza A, in PPP could be overcome by a pelleted formulation, the composition of which can delay release of the a.i. The technology allows protection of crops from soil-borne, as well as foliar sucking and biting pest damage by controlled release into the soil to allow uptake into plant vascular system.

In the field crops are subject to a wide variety of biotic and abiotic stresses. In order to manage crop protection effectively it is important that we understand not only the way plants respond to these stresses, but the way in which these responses interact. High levels of fertilisers and pesticides are often applied to maintain soil nutritional status and prevent disease in modern intensive farming systems. Potassium (K) is an essential element for plant growth and development, and is required for a wide variety of processes within the plant. These processes can be broadly divided into biophysical processes such as stomatal opening and cell extension and biochemical processes such as protein synthesis and enzyme activation. K starvation has been shown to lead to increased levels of the stress hormone jasmonate (JA) and related compounds in Arabidopsis thaliana plants which in turn modulates the plant’s defence against herbivorous insects and probably other pests or pathogens (Armengaud et al., 2004; Troufflard et al., 2010). In order for these results to be applicable to agriculture it is important to assess whether crop plants respond to K in a similar manner as the model plant. In this project the effect of K-deficiency on growth, metabolite concentrations, transcript levels and pathogen susceptibility of barley were investigated. Plants were grown in full-nutrient (control) or K-free hydroponic culture. The physiological, biochemical and transcriptional effects of K-deprivation were accessed over a time course of 20 days. Roots and shoots from plants grown in K-free nutrient solution had significantly lower K concentration than those grown in the control solution after 3 and 6 days respectively. A significant reduction in growth was seen as early as 6 days after K withdrawal. K-starvation led to a slight decrease in nitrogen metabolism, while hexose sugars strongly accumulated. By day 9 a significant increase in the expression of JA marker genes was seen in plants grown in K-free nutrient solution. Thus, despite possible differences in downstream events an induction of JA biosynthesis in response to K-deficiency occurs in both Arabidopsis and barley. Detached leaf segments were used to assess the effect of K-deficiency on infection of barley by two fungal pathogens with different strategies for nutrient acquisition. K-deficient barley plants were less susceptible to the biotroph Blumeria graminis f. f. sp. hordei (powdery mildew) and more susceptible to the hemi-biotroph Rhynchosporium secalis. Treatment of detached leaves with methyl-jasmonate (Me-JA) also led to less B. graminis infection, but had no effect on the R. secalis infection, indicating that JA increase in response to K-deficiency influences B. graminis but not R. secalis infection. The study therefore provides strong evidence that the effect of K-deficiency on pathogen susceptibility is determined by the JA-sensitivity of the pathogen.

The approach used in this study tested the application of an isotope dilution technique (ID) as a means of measuring the labile U(VI) and Th pools in soils. Uranium and Th lability and solubility were investigated for two sets of soils. The first set (Field soils) consisted of thirty seven soil samples representing five contrasting local ecosystems; the second dataset (BGSc) included 40 soils sub-sampled from the British Geological Survey (BGS) archive. Field soil pore water samples were taken from soil columns held at close to field capacity to measure U and Th solubility and speciation; the effects of time, temperature and reducing conditions on Th and U speciation were investigated. Soils were extracted with foursingle extractants: CH3COONH4, EDTA, 0.43 M HNO3 and TMAH to determine their ability to solubilize labile U and Th. Solubility of Th and U varied with soil characteristics, influenced by pH, DOC, DIC and phosphate concentrations. The Kd values for Th and U varied by 4 and 3 orders of magnitude respectively over the range of soils studied. The formation of soluble uranyl carbonate complexes give rise to a strong positive correlation between U and DIC concentrations in soil solutions. This was particularly clear under anaerobic conditions and also at high temperatures which encouraged microbial activity and high CO2partial pressures. Isotopically exchangeable 238U(VI) (the ‘E-value’, UE) in the soils studied varied from 2.7 to 39.1% of the total soil U content. On average, over all groups of soils, CH3COONH4, EDTA and TMAH underestimated E-value by factors of 13.7, 9.5 and 1.6, respectively, while extraction with 0.43M HNO3 overestimated E-value by only a factor of 1.04. Thus, on average across a range of soils, dilute nitric acid gave the best estimate of E-value compared to other extractants. Generally, E-values for U(VI) did not correspond consistently with any single chemical extraction procedure although the degree of correspondence was soil-dependent. Using UEand ThTMAH as input parameters in the geochemical speciation model WHAM-VII improved the prediction of U and Th solubility compared to using the total metal content orthe pools extractable by (other) single extraction methods. Finally, preliminary experiments confirmed the validity of ID for measuring labile soil Th without disturbance of soil-solution equilibrium.

Determining the total concentration of elements in soils seldom provides sufficient insight into trace metal bioavailability. However, measurement of ‘isotopically exchangeable’ metal can provide a better evaluation of metal reactivity and potential toxicity. Traditionally this requires the use of problematic radio-isotopes (e.g. 109Cd (γ)). Fortunately, increasing access to Inductively Coupled Plasma Mass Spectrometry (ICP-MS) in recent years has led to greater use of enriched stable isotopes of trace metals. The lability of heavy metals has been determined through a variety of approaches, including single and sequential extraction or predicted by geochemical models. In the present work, multi-element stable isotopes methods were developed for simultaneously determination of the labile pool of Fe, Zn, Cd and Pb using isotopic exchange principles. This included experimental and instrumental development for an accurate and precise determination of labile metal pool in soils. This approach was then validated by quantifying Zn, Cd and Pb in contaminated soils (Derbyshire; n = 8 and Weardale catchment; n = 246) and comparing the outcome results with common traditional extraction procedures. The variation of metal lability with soil characteristics was used to predict metal lability from the simple soil measurements using a multiple regression approach. In addition, E-values of Fe, Zn, Cd and Pb was used as input to WHAM(VI) (Windermere Humic-Aqueous Model) to predict metal solubility, emphasising in the role of Fe under reducing conditions in this regard. The results showed that isotopic dilution is a robust mechanistic method for assessing the ‘reactive’ pool of multiple trace metals over a wide range of soil characteristics. The results showed a very wide range of metal reactivities (almost 1%-100%) for Zn, Cd and Pb that were consistent over a range of spike concentrations. Sub-micron forms of non labile metal are perhaps most likely to occur in suspension either strongly bonded to humic/fulvic acids or occluded within CaCO3 particles. It appears that E values have no consistent correspondence to any chemical extraction procedure. Nevertheless, the use of 0.43 M HNO3 to extract labile metal in organic soils at pH < 6 appears justifiable - especially where humus is likely to be the principal adsorption surface. It is also important to acknowledge that extractions are not necessarily intended to estimate the entire reactive fraction. Thus, DTPA has been successfully applied as an empirical prediction of plant uptake but its extraction capacity is particularly limited in calcareous systems where it substantially underestimates the isotopically exchangeable metal pool. Speciation calculations showed that prediction of metal solubility was much better when the isotopically reactive metal pools were used as input to WHAM(VI). The soil samples that fitted best had pH values less than 4.0 and high organic matter contents reflecting the strength of the humic binding component of WHAM(VI) particularly in the case of Zn. The changes in metal solubility and lability under reducing conditions were mainly affected by pH. Moreover, the measurement of Fe2+ in the solution phase was considerably lower than that of the isotopically labile Fe2+ which calls into question the dependence on soluble Fe2+ to predict reductive dissolution of Fe-oxides. In addition, under reducing conditions the variables input of Fe to WHAM(VI) showed greatest effects on predicting metal solubility. It was found that Zn and Cd were affected only by Fe2+ competition for adsorption sites while predicted Pb solubility was more affected by loss of oxides than competition processes. The fractionation results, output from WHAM(VI), showed that a significant proportion of Pb was associated with Mn-oxides. Therefore, the calculation of loss of the adsorption site of Mn-oxides depending on Mn2+ measured in the solution phase did not improve the predicted Pb solubility where the model underestimate the adsorbed labile Mn as inference from Fe results.

This thesis is an attempt to estimate the regional and national economic consequences of a wholesale move to sustainable agricultural systems in the UK. The study reviews definitions of agricultural sustainability, and draws a distinction between sustainable and organic farming systems. Farm-level definitions of sustainability are developed for all the main farm types encountered in the UK, and key indicators with targets are developed to assess and monitor any move towards sustainability. Linear Programming models are constructed, for 23 representative UK farm types under conventional and sustainable farming scenarios, to estimate the farm-level impacts of the adoption of sustainable farming at some point in the future. The farm-level models are aggregated to regional and national levels to estimate the likely changes in UK agricultural production of a more widespread adoption of sustainable farming practices. The wider economic effects of these changes at the regional and national levels are then examined by the use of output, income and employment multipliers. The study found that the biggest financial losses were predicted to be on intensive livestock farms, and in the more productive agricultural regions in the East and the South. Losses in net farm income were greatest on pig and poultry farms on which incomes fell to 33% of the conventional incomes, specialist dairy incomes fell to 47%, and on mainly dairy farms they fell to 58%. Average incomes on cropping and large LFA farms fell only slightly to 97% of the conventional scenario, whilst incomes on small LFA farms rose slightly to 102% an on mixed lowland farms they increased to 119% of the conventional scenario. The aggregated results project a fall in total net farm income for the UK to 85% of that under conventional farming. However, the total net farm income for Scotland would rise, whilst the biggest losses would be projected for Wales and Northern Ireland. Agricultural output was projected to fall by £2.42 billion, leading to an indirect fall of £1.58 billion in the farm supply industries, and a further induced fall of £1.68 billion in household spending, totalling a net loss of output of £5.66 billion. There would be a negative direct effect on household incomes however of £167 million, with indirect losses of £84 million and induced losses of £565 million. Direct employment in agriculture was also projected to fall by 28,830 FTEs, which would lead to an indirect loss of 31,740 FTEs in industries supplying farming, and induced losses of 30,292 FTEs in the wider economy leading to an overall loss of 90,862 FTEs. Gains in direct agricultural employment were however projected for the South East of England, and the West of Scotland. The North West of Scotland being the only region, where there would be a net overall increase in employment. Nationally sustainable agriculture would lead to a significant fall in the total income from farming, yet there would be substantial variations around the country, and between farm sectors. Indirect effects on the farm supply industries, and induced effects on households spending would lead to substantial losses, which would need to be offset against the environmental gains. The implications of these results for agricultural policy are discussed.

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.