The study seeks to develop a field water management system for agriculture in peat soils in Malaysia, with an overall approach of integrating the engineering and agronomic aspects associated with crop production in deep peat areas. This includes the determination of soil physical parameters essential for field drainage design. The main experiments were carried out on a 10.9 hectare plot of land, initially drained 15 years earlier. The results were compared with data collected from a newly opened area and an area drained 40 years earlier.

The understanding of the mechanical behaviour of natural turf pitches is limited, owed in part to the deficiencies in current testing devices and methodologies. This research aimed to advance the understanding of surface mechanical behaviour through in-situ and laboratory experiments, and via the development of new testing devices. An impact testing device, the Dynamic Surface Tester (DST) was developed, with impacts replicating the magnitude of stress applied by athletes onto turfed surfaces during running. Developmental experiments indicated that the device was sensitive to changes in soil condition due to variations (P<0.05) in impact data.

Many hydrophobic pollutants can be emitted to agricultural soils if sewage sludge is used as a fertiliser. The fate and effects of pollutants in such receiving environments are relatively poorly understood compared with our knowledge of chemical behaviour and impact in surface waters. One chemical of particular concern is triclosan because it has antimicrobial properties which could affect important soil functions. Triclosan is hydrophobic, which means it will sorb appreciably to organic solids and is not readily biodegradable. It is also used extensively in personal care products. These factors have prompted considerable attention in the literature with respect to its environmental profile. In recent years, this attention has shifted away from the water environment to terrestrial systems. This thesis bridges some of the knowledge gaps considering the fate (specifically mineralisation, primary degradation and the formation of bound residues) and the effects (to the soil function and phenotype) of triclosan in soils amended with biosolids. Cont/d.

Bacteriohopanepolyols (BHPs) are a group of membrane lipids produced by a wide range of bacteria which have a high degree of structural specificity relative to bacterial source. This is the widest study to date into the BHP content of soils from around the world and investigates their use as biomarkers in modern soils and modern and ancient sediments using reversed phase HPLC-MSn. A total of 46 different BHP structures were observed during the study including the tentative identification of 11 novel BHP structures. Analysis of the BHP content in a series of soils from North East England, South West England, Canada, Sweden, Vietnam and Southern Spain has shown that soil BHP distributions are dominated by up to 5 different BHPs: bacteriohopane-32,33,34,35-tetrol (BHT), 35-aminobacteriohopane – 32,33,34-triol (aminotriol), 30-(5’-adenosyl)hopane (adenosylhopane), bacteriohopanetetrol carbopseudopentose ether (BHT cyclitol ether) and, less frequently, adenosylhopane type-1, although generally more than 20 different BHPs are identified in each soil sample. Soil bacterial population dynamics were investigated using existing knowledge of the relationship between BHPs and their specific bacterial sources and has demonstrated, for example, a decrease in the concentration of cyanobacteria related BHPs with soil depth in pasture (Palace Leas) and woodland (Hack Hall farm) environments confirming the validity of these BHP – bacteria relationships to infer BHP producing bacterial activity. Principle Component Analysis of the different bacterial types, identified by source BHPs, in the different soils can clearly identify variations between the soils with, for example, the influence of methanotroph and cyanobacteria derived BHPs having significant and opposite effects on the separation of the soils. This potentially enables BHPs to be used to identify source locations or environments. Investigation of seasonal variations at two sites in NE England (Palace Leas and Hack Hall Farm) has shown that soil BHP concentrations increase during the summer months and decline during winter with no net accumulation indicating that the aerobic conditions observed in near surface soils result in the rapid diagenesis or metabolism of BHPs. An investigation of estuary sediments from the Congo Fan, River Rhone and 7 arctic rivers has shown that this rapid degradation of these highly functionalized structures does not occur in anaerobic marine sediments with the aerobic methane oxidizing bacteria biomarker, 35- aminobacteriohopane-30,31,32,33,34-pentol (aminopentol) and other complex BHPs being identified in Congo Fan sediments up to 1 million years old (100 metres below sea floor), thus enabling BHPs to be used as biomarkers in palaeo-environments. The estuary and fan sediments also contained a suite of BHPs that are ubiquitous in soil but absent in many lacustrine and open marine environments where their concentration decreases proportionally with distance from land. These BHPs; adenosylhopane, adenosylhopane type- 1 and their C-2 methylated homologues can therefore be used as markers for the transport of soil derived organic material (SOM) from terrestrial to marine environments. These results have opened up a wide range of opportunities for BHPs to be used as bacterial proxies in a variety of environments and ages, accessing a wide range of different proxies for different bacterial populations and processes from a single analysis.

Previous work at IGER has revealed that soil structural differentiation under white clover is phenomenally rapid and enhanced when compared with ryegrass. White clover is one of the most nutritious and widely distributed forage legumes. Its use is advocated in sustainable systems of livestock production because of its ability to acquire atmospheric N through biological fixation in the root nodules. It thus provides an economically viable alternative to the N-demanding conventional system, and a possible solution to reduce the environmental impacts of nitrate leaching from agricultural land. There are, however, potentially negative impacts associated with improving soil aggregation through the use of clover that need further investigation. It appears that legume-based systems are not environmentally benign: similar amounts of N and P are leached from beneath grass-clover swards as those leached from beneath fertilised grass operating at the same level of production. In some circumstances, clover rich swards can give rise to very high levels of nitrate leaching. Thus, this observation of clover induced soil aggregation has important implications for the pollutant transport qualities of soils and for the organic/conventional agriculture debate. Re-packed soil columns of four soil series and 0.5 m intact monoliths of the Crediton series were planted with white clover, perennial ryegrass and a mixture of the two species, and managed according to an organic and conventional farming regime. Visual observations revealed a rapid enhancement in soil structure beneath white clover compared to ryegrass and unplanted soil. A novel technique to determine oxygen diffusion as an indicator of soil porosity, gave a diffusion rate that was nearly nine times greater than that of the grass treatments and fifteen times greater than the unplanted control soil, with intermediate values for the mixed treatment Thus enhanced structural differentiation beneath white clover was supported by greater permeability to air and freer drainage to water. Structural stability tests suggested that white clover improved the ability of the soil to maintain its structure under the action of water, and was estimated to be three times more stable than ryegrass. There was also evidence which implied improved shear strength and resistance to mechanical forces. Differences in soil structure were verified with water retention measurements, which showed a greater proportion of macropores. The void structure was simulated with the 30 Pore-Cor network model, which also suggested a number of larger pores and a saturated hydraulic conductivity which was four times greater than ryegrass. This also highlighted inadequacies in the current standard ISO protocol for water retention. The solute transport studies showed elevated levels of nitrate and phosphate leaching. Concomitant transport of bromide inferred structural differentiation and changes in leaching dynamics. In addition, white clover allowed the passage of greater volumes of water. Most importantly, this was manifested at the soil profile scale and therefore likely to be of consequence in the field. The implications of the research are that enhanced soil structure beneath white clover alters the transport of gases, water, nutrients and other dissolved substances. Further understanding of these soil processes are needed before advocating the use of forage rich legumes in sustainable systems, and for the development of management strategies.

The environmental risk assessment of GM plants is a fast moving area of science. Much research has focused on developing methods to evaluate potential effects on a range of organisms. Microorganisms play an essential role in many soil processes, with the rhizosphere as the prominent site of microbial activity. There is a general need for protocols to assess the effect of anthropogenic influences, the use of different crops and crop rotation an.d as well as GM plants, on the microbial community within the soil. The rhizosp~eres of three crop plants Brassica napus (Oilseed rape), Triticum aestivum (Wheat) and Solanum tuberosum (Potato) were compared using both genetic and functional diversity methods. The rhizospheres of four cultivars of potato were compared; GM potato (variety Kardal) modified with an anti-fungal transgene, GM potato (variety Kardal) with no transgene inserted (empty vector), parental .- line of potato (variety Kardal) and a different cultivar (variety Russet-Burbank). Genetic diversity of bacterial populations isolated from the rhizosphere were compared using PCR amplified DNA of 168 rRNA with denaturing gradient gel electrophoresis (DGGE) to obtain community fingerprints. Activity of the microbial populations was assessed using Biolog G.N MicroPlate™ community substrate utilisation and enzyme activity using a microplate method based on substrates linked to the fluorescent compounds methylumbelliferone (MUB) and 7-amino-4-methyl coumarin (AMC). By comparing the ~M plants to non-GM plants and other crops, observed differences are placed in context. This work shows that the GM line examined.appears to have little effect on soil microbial populations. Detected effects of1he GM potato line were minor compared with other sources of variation observed between plants cultivar or crop species, management practices and sampling time. To date, there has been little evidence that cultivation of GM plants leads to significant changes in microbial popUlations.

No description available.

No description available.

As the UK’s largest non-government land-owner, the National Trust is committed to reducing its impact on climate change, recognising the importance of soil organic carbon (SOC), and its need for preservation. To establish if land-management could be optimised to increase carbon storage, ‘The Wallington Carbon Footprint Project’ was implemented. This study aimed to measure the Wallington Estate’s carbon stock, establish what controls SOC, identify carbon under-saturated soils, and make land-management change to increase SOC. To achieve these objectives a soil sampling campaign and land-use survey were undertaken at Wallington, with further sampling at a verification site in Cambridgeshire. Land-use intervention trials measuring carbon fluxes and SOC change were combined with computer modelling and questionnaires, to assess the impacts of land-use and management change on SOC. A land carbon stock of 845 Kt (60 Kt within biomass, and 785 Kt within soils) was estimated for Wallington, with the greatest control on SOC identified as grassland landmanagement. Other controls on SOC were: land-use, soil series, altitude, soil pH and landuse history, indicating that these should be used in all estimates of SOC distribution and stock. A possible link between phosphate fertilisation and SOC accumulation under grassland was identified; however this was not confirmed in a year long field trial. Incorporation of charcoal into soils was identified as a method of carbon sequestration, with a simultaneous reduction in nitrate loss from soil. Surface application to grasslands revealed no detrimental effects on soils, grassland productivity or water quality. Further trials investigated the impacts of arable conversion to short rotation coppice willow, and of peatland afforestation, both indentifying losses of SOC following the land-use change. Measurement of biomass carbon gains, full life cycle assessment of the each landuse, and the impacts of varying types of biochar are required before firm conclusions regarding land-use change and carbon sequestration can be made.

The development of high throughput sequencing techniques has allowed for greater investigations into environmental microbial communities in this thesis. Using the Illumina Solexa sequencing technology we investigated prokaryote communities in replicate soil samples from four soil types: both the organic and mineral layers of two UK forest sites, an oak stand and a Corsican pine stand. Prokaryote diversity was assessed using the 16S SSU rRNA encoding genes from DNA and rRNA (reverse transcribed to cDNA) extracted simultaneously from the same sample. From a total of > 4.5 million sequence reads, only 0.6 % of the reads overlapped between RNA and DNA samples. Marked differences were seen between the distribution of Phyla from RNA and DNA. The community structure showed a small number of Operational Taxonomic Units (OTUs) having high relative abundance and many OTUs being detected in low or single numbers, representing a ‘rare biosphere’ community composition. Taxonomy of RNA was further described at phylum and family level. Only 30 % of OTUs could be assigned taxonomy at phylum level and, of those, only 46 % at family or genus level (bootstrap support >70). At phylum level, the RNA samples were homogeneous across all soil types, dominated by β/γ-Proteobacteria, α-Proteobacteria and Acidobacteria. 7 phyla were detected in all samples and rarely detected phyla showed high diversity between samples. At family level the samples were much more heterogeneous, different phyla showed different family taxonomic distribution patterns, with Firmicutes and Actinobacteria the most diverse. We used principal component analysis comparing 27 environmental variables against the Shannon-Weaver diversity index of each soil sample. Each soil type was seen to have its own unique fingerprint of diversity. pH was observed as the most influential parameter to diversity, and C:N ratio, zirconium and zinc levels also considered important. 24 of the 27 parameters explained the majority of the variation in the diversity of the soil samples, concluding that prokaryote diversity in these soils is determined by complex interactions between a wide range of environmental conditions. Together this demonstrates that the prokaryote soil community are extremely diverse and dynamic.