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No description available.

The discrimination of crops, weeds and soil by optical reflectance was tested for broccoli, cabbage and leek crops from several different farms. The effects of crop varieties (in particular cabbage), weed population and type of soil did not affect the discrimination accuracies. No effects on crop/weed/soil discrimination were noted from the analysis of stressed crop samples (nitrogen concentration and water stress). Crop growth stage also had no influence on crop/weed/soil discrimination. Crop/weed/soil segregation into their respective groups required the use of classifiers. Two sets of spectral measurements, each comprising three wavelengths, were selected from all the data analyses providing the best overall accuracies. Discriminant analysis provided classification functions which differed greatly between farms. Neural networks provided the final algorithm relating the wavelength sets obtained by discriminant analysis. The use of broadband spectral range for discriminating between crop, weed and soil was also considered. This algorithm based on the discriminant integration index, also uses the discriminant analysis results to obtain the spectral range, but requires only one filter for accurate plant recognition. High discrimination accuracies are achieved with both algorithms and the broadband filter system shows potential for simplication without loss of performance in distinguishing between crops, weeds and soil.

This interdisciplinary research combines ecology with social anthropology and uses a case study of a Romanian mountain village to investigate the role of pastoralists in conserving agricultural biodiversity. More specifically, the aim of the ecological aspect of the research is to analyse the relationship between land management practices and the butterfly fauna of hay meadows. Butterflies were chosen as the focus of the ecological component of this work in light of their ability to act as indicators of the state of semi-natural habitats. The results indicate that the current spectrum of hay meadow management intensities conserves a range of butterfly species associated with semi-natural grassland habitats. The number of species declines as management intensity increases and this trend indicates that intensification in management beyond current levels would lead to a comparatively depauperate butterfly fauna. However, the cessation of hay production in the village, which in the long term also causes a decline in the number of butterfly species, is a more probable scenario, taking into account the constraints of the natural environment and the likely decrease in the need for smallholdings to act as a livelihood ‘safety net’. A more pressing social factor that threatens the functioning of the livestock production cycle is the rejection of shepherding as a livelihood. The development of measures aimed at conserving semi-natural grasslands and their associated species needs to take a holistic approach to supporting the functioning of the livestock production systems that sustain these habitats. The social factors that act as a constraint on the functioning of the systems must be addressed but it is also important to capitalise on the cultural elements of pastoralism that may slow the trend of abandonment and may potentially increase the uptake of voluntary conservation schemes.

Methods for examining how the errors of agricultural field plot experiments are related to the distances between plots are developed for a two-dimensional layout. Knowledge of the errors is useful for investigating the suitability of experimental designs and methods of analysis for various field situations. The methods of postblocking and pairblocking are extended to two dimensions to allow the calculation of error laws for the semi-variance of the difference in yields of plots <i>p</i> rows and <i>q</i> columns apart. The techniques are applied to results of past variety trials. The two dimensional version is applied to two UK trials series, while the one-dimensional version is applied to a tropical series of trials. The error laws derived, the exponential variance error laws, are used to improve recommendations for design and analysis of future trials. The classical method of analysis of the variety trials used is also described in this work and the efficiency of such analysis assessed. In particular, for row and column designs that have the property of adjusted orthogonality, the estimate of the ratio of the row stratum variance to the row x column stratum variance can be expressed as a function of the error mean squares from the analysis of the incomplete block column component design and row and column design. Similarly, the estimate of the ratio of the column stratum variance to the row x column stratum variance can also be expressed as a function of the error mean squares from the analysis of the incomplete block row component design and row and column design. Knowledge of the error variance law can be used to derive spatial methods of analysis for individual trials. The simplest first difference neighbour analysis, derived from the linear variance rule has row and column analysis without recovery of information as its simplest case when no trend effect is present.

A set of equations suitable for describing the dynamics of a liquid droplet - gas mixture (spray) have been developed. The equations are arrived at by considering the spray as a multiphase continuum within which the gas and droplets of different sizes constitute individual phases. By ignoring droplet-droplet interactions and considering the gas phase as an inviscid fluid a simplified form of the equations of motion has been arrived at. The equations are considered in one dimension and used to describe the dynamics of the interior of spray produced by a large or medium scale irrigation sprinkler. When combined with data representing the distribution of droplet diameters within the spray this model can be used to predict the water application produced by a sprinkler operating in windy conditions. Such simulations have been undertaken to predict the water application from static sprinklers and the results validated by comparison with data obtained experimentally. A simulation methodology is used to determine the uniformity of water application produced by a travelling sprinkler. By considering the results of large number of simulations produced using meteorological data spanning several years the manner in which the simulation can be used for determining optimum irrigation practice is demonstrated. A simple model has been developed for predicting the water application from a travelling sprinkler operating in still air. The model can be used for obtaining first approximations to optimum operating conditions and provides a means for easily quantifying the performance of a given sprinkler. Further use of the model may be made for aiding in the design and control of irrigation sprinklers.

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The overall aim of this thesis was to develop a better understanding of the role of prescribed burning in moorland management within the Peak District National Park. These moorlands are dominated by heather (Calluna vulgaris (L.) Hull). Prescribed burning is a management tool that used routinely to manage moorland vegetation for grouse and sheep production. The aim is to remove the above-ground foliage and allow the Calluna to resprout from the burned stems. Normally such prescribed burning is done on a rotational matrix, and the aim is to provide a continual supply of moorland vegetation in different stages. This thesis attempted to answer the following questions: (a)How degraded are the moorlands in the Peak District, and does prescribed burning affect species density and restoration potential? (b) What are the environmental factors that influence the response of the plant communities, and how do the constituent species respond after prescribed fire?) (c) Does prescribed burning affect soil chemical properties? (d) What factors affect biomass reduction in prescribed fires on upland moorland? (e) What changes in above-ground biomass, carbon and nitrogen occur during this burning The context for this work is that British moors are high-priority habitats for conservation and it is increasingly recognized that they provide important ecosystem services (carbon accounting, water provision). A combination of field survey and experiments was used. A chronosequence study carried out on five replicate moors showed the vegetation was severely depauperate relative to the species that might be expected in pristine moorland vegetation. Moreover, the seed bank was also depauperate and propagules must be added to restore them. There was an increase in species richness immediately following prescribed burning with a subsequent decline with time. Multivariate analysis produced two gradients, a continuum from relatively lichen-rich vegetation to a graminoid-dominated one, and (b) a post-fire growth response of the Calluna. Calluna was the only species to show increasing growth after burning; all other species were reduced in the oldest vegetation. A similar study of soil properties showed that prescribed burning had a limited effect; some chemical properties changed with the burn-recovery cycle. In order to develop an improved method of prescribed burning the relationship between fire severity and both fire characteristics and environmental variables was assessed experimentally. The results were inconclusive but suggest that the burns with the highest temperatures were flash fires whereas the burns with the lower residence times were smouldering fires that probably converted more biomass to charcoal). A study of prescribed burns showed that the loss of biomass during prescribed burning was very variable and this almost certainly reflected a range of environmental and management factors. The burning method used in the Peak District is designed to minimize biomass loss and it was demonstrated that in some burns this was very successful. The accumulation of above-ground biomass was measured after burning and the oldest stands had much greater biomass values than literature ones and no sign of an asymptote at 50 years.

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This thesis reflects critically on how a formalized and supported artisanal and small-scale mining (ASM) activities - low tech, labour-intensive mining excavation and processing - can alleviate poverty and facilitate local economic development in rural Malawi. As is the case throughout sub-Saharan Africa, in Malawi, to date, there has been strong emphasis on a 'small farm first' approach to poverty alleviation, despite mounting evidence of its limited impact. The situation is particularly important at present: although farm productivity has diminished considerably in the country in recent years, and it is becoming increasingly difficult for people to subsist off of its activities alone, support for agriculture continues to be the centrepiece of the country's rural development and poverty alleviation strategy. The inability of agriculture to fulfil this role has induced many thousands of the country's rural Malawian families to ' branch out' into the nonfarm economy - dynamics which the country's policy-makers have yet to recognise. In line with the livelihood diversification trend that has emerged throughout most of the Southern African Development Community (SADC) and sub-Saharan Africa more generally, in Malawi, movement into ASM has become one of the most important avenues followed, providing much-needed economic relief for many rural households. In Malawi, which, despite being perceived as a non-extractives economy by both government and donor officials, and therefore lacking the policies and programmes to readily-ignite the sector's expansion, the available evidence also points to ASM having become a rooted livelihood activity for many subsistence people across the country. Integrating the sector into development plans, however, will require sweeping change because its activities are largely unsupported, monitored by government and for the most part, carried out illegally - direct outcomes of the low priority the sector receives at the policy level. What role does ASM now play in the livelihoods of rural Malawians, and can it be readily showcased in the country's economic development plans, which again, are very much built around the idea of a supported smallholder economy alleviating hardship? Focusing on the cases of artisanal gemstone and limestone extraction, the thesis aims to broaden understanding of the challenges and merits of developing a more formalised and supported ASM sector in Malawi, as well as the efficacy of promoting it - against the background of the current policy stance - as a new avenue for poverty alleviation in the country. Drawing on documentary analysis and feedback from interviews, the thesis surveys the perspectives of the country's key stakeholders at both the policy and grassroots levels, including government, donor and NGO officials, farmers and miners themselves. Findings provide important insight into how ASM currently contributes to rural livelihoods, and its emerging linkages with agriculture and other nonfarm activities, in the country. From this analysis, critical reflections are provided on whether giving greater priority to the sector's development and in poverty alleviation policies is a realistic option at this point in Malawi.