Issued also as thesis, University of Michigan. / Bibliography: p. 203-210.

No description available.

Under intensive farming, soil structure degradation and soil erosion are primarily associated with losses of organic matter. Restoration of soil structure may depend on the amount and nature of the organic amendment added. The effect of the addition of humic and fibric materials, and beeswax, a naturally occurring source of long-chain aliphatics comparable to those present in humic materials, on microbial activity and the structural properties of a waterlogged silty clay low in organic carbon was investigated. The incorporation of the fibric material increased the microbial activity in proportion to the amount of material added, whereas the humic and beeswax materials had the opposite effect. All organic materials added increased the cohesion of aggregates due to non water-dispersible cements. The fibric material was predominantly composed of polysaccharides and large quantities were required to produce a positive effect. The humic material was mainly lipids and the effect was associated with the time of incubation rather than the amount of material added. Principal-component analysis showed that the humic material was more effective at stabilizing soil aggregates than the fibric material, although the fibric material had a greater effect on the resistance of aggregates to slaking forces. Further testing with beeswax showed that the clay-associated lipids increased by 3.5-4.0 times the resistance of soil aggregates to the slaking forces, whereas the effect of hydrophobic "free" lipids was transient and accessory by coating and embedding soil aggregates.

The overwhelming focus of documentary sources indicate that traditional approaches to land degradation and soil erosion in South Africa have focussed on the physical dimension of the problem and the development of practical solutions to its reduction. This study was undertaken from the viewpoint that this emphasis has resulted in the neglect of other (for example, socio-political) aspects of soil erosion and that such neglect has exacerbated the soil erosion problem manifest in South Africa. An examination of the 'human dimension' of soil erosion in South Africa was therefore undertaken through an analysis of soil conservation policy and legislation promulgated to effect policy objectives between 1910 and 1992. Acknowledging that the policy environment is influenced by factors within the economic, political, historical and perceptual (all human) environments, as well as the natural environment, this study attempts to integrate information relating to each of these parameters within the overall framework of South African soil conservation policy. Particular emphasis is placed on the role of environmental perception in the decision-making process, together with the critical influence of intervening variables found to be operative within the perceptual environment as represented in the South African context. In the absence of substantive empirical data, this study posits a number of a priori assumptions regarding the extent and causes of soil erosion, support for which was initially derived from the extensive literature sources reviewed for the study. The basic premise of this study is that soil erosion persists in South Africa, and despite considerable government and public inputs and participation, and the existence of a legislative machinery created specifically to address the problem, progress in promoting soil conservation through implementation of specific measures has been slow. Following a review of soil conservation policy and legislation up to 1992, it is further submitted that factors other than legislative inadequacies could account for this problem and therefore warrant particular and thorough investigation. To this end, this work firstly describes the physical context within which South African soil erosion occurs, followed by a brief appraisal of socio-economic and political variables which together have shaped contemporary perceptions regarding the nature, extent and causes of soil erosion in the country. A comprehensive review of relevant policy and legislation in the period 1910-1992 was then undertaken by reference to published and unpublished sources. The evolution of soil conservation policy in the country was charted through reference to relevant legislation and parliamentary debate. The temporal variation in the relative success of the policy and legislative enactments was measured by reference to relevant indicators. The adequacy of South African soil conservation (as indicated by four key legislative enactments formulated to specifically address soil erosion) was evaluated using key elements of the World Soils Policy as a baseline. Analysis of the Forest and Veld Conservation Act of 1941, the Soil Conservation Act of 1946, the Soil Conservation Act of 1969 and the Conservation of Agricultural Resources Act of 1983, revealed a clear evolutionary progression in which successive acts sought to build upon successes and minimise the weaknesses of previous efforts. This analysis reveals marked temporal variability in the extent to which each element is addressed and explores the multi-environmental (political, social, historical, economic and perceptual) constraints on attainment of all goals. This assessment permitted the compilation of, what the author has termed the South African Policy Environment Model, which takes the form of a working hypothesis. This hypothesis was subsequently tested utilising the 103 responses obtained from a postal questionnaire survey directed at 242 scientists, policy developers and extensionists (representing a 43 per cent return), that is, those persons who either currently or during the study period, were actively involved in the development of soil erosion research and/or the implementation of conservation policy objectives. In spite of the apparent effort by the South African government to address soil conservation, contemporary opinion (according to documentary evidence) suggests that the policies formulated have failed to attain soil conservation goals and reduce the manifest extent and rate of land degradation in the country. This study broadly concludes that such inefficacy of policy may be ascribed to: 1. lack of importance ascribed to soil 2. national level control 3. non-uniformity in application of law 4. inadequacies in the implementation of policy 5. paucity of information on real nature and extent of problem 6. perceptions in an uninformed environment. The study furthermore submits that images concerning the realities of soil erosion are shaped by perceptual filters and the value systems of individuals active in the soil conservation arena, or more specifically, key players' perceptions regarding the causes, extent and nature of the soil erosion problem, are what underpin and ultimately give rise to the relative effectiveness of soil conservation strategies. This study identifies a multiplicity of factors which operate within five dynamically interative environments (the political, economic, historical, perceptual and natural environments) considered influential in shaping the temporal (and spatial) variation in the policy environment represented in this study. This examination of the multidimensionality of soil erosion has led to the conclusion that in addition to the problems broadly outlined above, soil erosion is also a problem of: 1. accountability; 2. focus; 3. priorities and government commitment; 4. situational incompatibility; 5. misinformed perceptions; and 6. timing. It is submitted that lack of recognition of these inter- and intra-environment dynamics could account for the relative inefficacy of soil conservation policy to promote the sustained adoption of conservation practices. Such factors will in the past have been overlooked due to the neglect of the 'human dimension' of the problem in South Africa in the period under review. It is believed that the measure of consensus derived from the results of this study, reflects contemporary realities concerning the status of soil conservation in the country, at least amongst those individuals most intimately involved in the development, formulation and administration of soil conservation policy. As such it provides an appropriate foundation upon which to base future policy decisions and more importantly, to derive optimum compliance with conservation norms and standards of practice amongst land users. Only by recognising the multidimensionality of the soil conservation policy environment and its components, can the past inefficacies be overcome. It is submitted therefore that for South Africa to meet its challenges of the 21st century concerning the conservation and sustainable utilisation of soil, the priority of policy developers must be - the expedient adoption of a multi- and interdisciplinary approach to agricultural resource management, with particular emphasis on its 'human dimension' . / Thesis (Ph.D.)-University of Natal, Durban, 1996.

This thesis describes a comparative study of actual and potential soil erosion in the Wilderness area of the Umfolozi Game Reserve, and a biophysiographically comparable adjacent traditional KwaZulu landuse area. Estimates of temporal and spatial variations in eroded surfaces, sparsely vegetated surfaces susceptible to erosion, and active gullies were obtained from five sets of sequential aerial photographs taken between 1937 and 1983. Estimates of the potential influence of rainfall erosivity, soil erodibility, topography, and changes in vegetation communities and landuse practices on these variations, were extrapolated from these aerial photographs as well as from maps, field surveys, records and other studies. Interrelationships between these potential influences, and the extent to which they actually contributed to the temporal and spatial variations in the three 'erosion' surfaces, were assessed visually using a geographic information systems thematic overlay technique, and computationally using a forward stepwise multiple regression procedure. / Thesis (Ph.D.)-University of Durban-Westville, 1990.

No description available.

No description available.

A study was conducted to determine if polyacrylamide (PAM) could be utilized as a best management practice to reduce soil erosion on forest road embankments. Experiments involving two different PAM application rates (10 and 20 kg/ha) were conducted using natural rainfall in 2001 and 2002 and indoor rainfall simulation. In 2001, PAM was combined with a broadcast application of grass seed. / The study results suggest that PAM provided no statistically significant erosion control after natural rainfall on a loam soil. In the rainfall simulation experiments PAM applied at both 10 and 20 kg/ha significantly reduced soil erosion (by 75 and 77%) and the turbidity of runoff water (by 99%). PAM application at 10 kg/ha significantly increased grass densities (by 109%) compared with the control plots. However, PAM applied at 20 kg/ha provided no significant increase in grass density compared with the control.

Thesis (M.S. - Soils, Water and Engineering)--University of Arizona, 1982. / Bibliography: leaves 81-83.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1986. / Includes bibliographical references (leaves 79-82).