This study investigates coal discard cover soil fertility and its potential for degradation, particularly in terms of its salinisation and acidification potential. Seven rehabilitated coal discard dumps in the Witbank, Ermelo and Newcastle regions were used as study areas. All areas were rehabilitated with a cover soil layer, revegetated and annually fertilised with nitrate fertilisers, super phosphate, kraal manure and lime. Performance guideline for pH of 5.5-(6.5 i0.5)-7.5 and electrical conductivity guideline of preferably less than 200 mS.rn-' but not higher than 400 mS.m-' were set based on literature information. Soil chemical data from a three-year fertilisation programme were used to assess the fertility of the cover soil surface (0-150mm). Data collected over a three year period as well as additional electrical conductivity and pH measurements from the cover soil surface, subsoil, cover soil/coal contact zone and underlying coal itself were used to assess the occurrence of salinisation and acidification of the cover soil. The soil fertility varied significantly among dumps as well as over the three years. Results indicated an increase in ammonium acetate extractable macro elements (calcium, magnesium and potassium). With the exception of manganese, no micro-element toxicities were recorded. Iron concentrations were slightly elevated in some of the sandy cover soil layers. No increase in soluble nitrogen (nitrate and ammonium) was found and most soluble nitrogen was in the form of nitrates. In general the Bray extractable phosphate increased during the study period. It can be predicted that with the following fertiliser programme increases of exchangeable macro-elements as well as available phosphorus can be expected. The study could not indicate an increase in adsorbed or available nitrogen. Organic carbon was initially not analysed therefore no comments can be made whether organic matter increased. Four of the seven dumps surveyed had comparably similar organic carbon levels to the background samples. Overall the fertiliser programme increased the electrical conductivity and decreased the acidity of the cover soil surface. Acidity and salinity was in general not a problem at the surface of the cover soil and pH was even slightly higher in cover soil samples. The acidity and especially salinity increased at the subsoil and so did the sulphate concentrations. Calcium and magnesium sulphate were predominantly responsible for higher electrical conductivity measurements. The percentage exchangeable sodium was also predominantly less than 2% indicating that sodicity is not currently a problem in cover soil. Soil fertility was satisfactory for vegetation growth and macroelement concentrations were in the correct ratio although calcium was slightly high. An elevated sulphate concentration, in comparison to the natural grassland soils, as well as a high salinity and high acidity in the subsoil layers indicate that salinisation and acidification could deteriorate without proper management. A slightly acidic cover soil can also be attributed partially to its natural acidic pH due to the wellweathered and leach property of burrow pit. Higher than recommended salinity levels were found in subsoil samples but the occurrence of acidification of the subsoil was more dump specific. In relation to acidity and salinity guidelines only the cover soil of one dump was concerning and the larger dumps subsoil acidity and salinity were elevated. The following management strategies are proposed: a) The acidification potential, and therefore the pyrite content of the coal discard must be considered during decisions making on the rehabilitation method (clay barriers), topsoil depth, maintenance and mine closure potential. b) The occasional monitoring of the subsoil's and coal contact acidity is recommended, although not much can be done to stop acidification after cover-soil placement. c) To ensure a more sustained from of nitrogen supplementation over the long term the use of selected legumes should be investigated. Research in Europe and Australia suggested that nitrogen fixation could contribute substantially to the nitrogen for plant uptake. d) The physical properties of the topsoil (bulk density 8 soil compaction) are also being neglected and needs to be assessed occasionally and interpreted together with chemical analyses. Observations in other studies indicate that this could be the most fundamental problem for vegetation growth and not necessarily soil fertility, since soil physical properties could have a major impact on root development. Key words: Coal discard, mine rehabilitation, soil fertility, topsoil degradation, salinisation, and acidification / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2004.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1974. / Bibliography: leaves 322-332. / xvii, 332 leaves ill. (some col.), maps

Light availability in forest understories is a well recognized constraint on sapling growth, but limitations in soil nitrogen (N) availability, and the link to foliar photosynthetic capacity, typically receive less consideration in describing stand dynamics. My primary hypothesis is that light and soil N availability have species-specific effects on photosynthetic activity and growth, and that together these resources will better define understory development in complex forests. To test these relationships, I examined 1) soil N indices and the tradeoffs between soil fertility and light attenuation in old-growth forest understories; 2) the effects of light and N constraints on understory sapling foliar N concentration (N%), N per unit area (Na), and natural abundance of ¹³C; 3) the effects of light and soil N supply on species growth and photosynthetic activity in a factorial field experiment; and 4) the mechanisms responsible for the stagnation of understory saplings. Soil N indices incorporating dissolved inorganic N and organic N were useful in characterizing differences in N supply among contrasting sites. Understory light availability declined with increasing soil N supply, while understory Abies lasiocarpa had strong correlations between foliar N% and soil N availability, despite shading effects. In partial-cut forests, understory Tsuga heterophylla and Picea glauca x sitchensis had consistent foliar N% across gradients of light availability; in contrast, foliar N% of Betula papyrifera and Thuja plicata declined with increasing shade, which would distort assessments of soil fertility and perhaps contribute to increased mortality of these species in deep shade. Strong correlations between foliar Na and ¹³C or growth increment suggest foliar N per unit area is the simplest integration of light availability and N nutrition on leaf photosynthetic activity. Ontogenic interactions that occur among foliar attributes and tree size in forest understories, especially for saplings < 1 m in height, contribute to time effects on growth patterns and emphasize the need for long-term studies of species autecology and stand dynamics. My experimental manipulation of light and N supply on saplings was ineffective, and future research using natural gradients in site productivity may be more fruitful in defining species response to light and N interactions.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 4 uppsatser.

Thesis (Ph. D.?)--Universitat Bayreuth, 2006.

Thesis (Ph. D.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 75-81). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 75-81). Also available on the Internet.

Thesis (Ph.D.)(Agricultural Economics)--University of Pretoria, 2007. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (MScFor (Forest and Wood Science))--Stellenbosch University, 2008. / This study sought to examine the effects of soil fertility replenishment (SFR) adoption on household security and poverty reduction in smallholder farming households of central and southern Malawi by assessing food security, asset status, and household income generating activities in Kasungu and Machinga Districts during 2007. The results showed that households had been able to significantly increase maize production by an extra 382 kg per year in Kasungu and 242 kg per year in Machinga Districts, which constitutes approximately 35% and 22% of average household maize requirements for the year for each district, respectively. This reduced the critical annual hunger periods from 3.46 months to 2.80 months per year in Kasungu and from 4.31 months to 3.75 months in Machinga. Respondents also reported a significant increase in assets and an increase in income. Despite these positive changes, households were found to still be living in extreme poverty. Selling physical assets was the most common response to shocks and any increase in income was allocated to the purchase of food, household supplies, and other items necessary to immediate survival. This study revealed that while food security is paramount to the sustainable livelihoods of smallholder farmers, livelihood security and poverty reduction depend on more than increased food production. SFR technologies are fulfilling their primary role as a means to food security, but their adoption does not lead to significant livelihood improvements. Achieving lasting impacts requires that initiatives take an integrated approach and address not only household food production, but the multifaceted dynamics of social institutions, markets/economy, and policy. The long-term impacts of the current agroforestry programs in the study areas will emerge only with time. Livelihood improvements will depend on several factors. First, market inefficiencies must be remedied and economic barriers must be broken down. Second, the challenges identified by the respondents, especially access to resources and training, need to be addressed in a participatory way that promotes education and empowerment. As these two issues are tackled, households will become better equipped to manage the complexities that arise from SFR adoption and livelihood diversification. It is recommended that future research and initiatives should focus on identifying and removing economic barriers to markets, addressing farmeridentified challenges such as access to seed, water, and education and training, supporting households in managing multiple livelihood strategies, and continuing research to identify appropriate agroforestry species and technologies.

Indigenous agroforestry systems, or the intentional use of trees and livestock in croplands, have a long history in the West African Sahel. In many locations, they have long contributed to food security and climate change resilience. But a century or more of cash cropping and use of modern agricultural inputs and tools has meant that no such agroforestry systems remain intact, and many are extinct, including in west-central Senegal, where the Serer historic mixed farming and pastoral strategies previously provided resilience to cyclical droughts and colonial-era agricultural and economic change but are now neither intact nor extinct. This study examines the current state of Serer agroecosystems, considering who uses what elements of the old systems, who has introduced what elements of nonindigenous farming systems, and whether this combination of local and imported farming systems is a coherent and sustainable fusion, or an incoherent pastiche leading toward agrarian collapse. I argue that, depending on how farmers integrate new models with the technical and cultural elements of the old system, a coherent fusion may result, with positive implications for sustainability, climate change adaptation, soil replenishment, crop yield, and livelihood resilience. This mixed-methods study draws upon literature from cultural ecology, agroecology, socioecological resilience, and history to interpret farmers’ accounts of changing agrarian practices. The study links ethnographic findings to empirical analysis of soil conditions and land use change. With these tools, my research sheds new light on the evolving role of local techniques and knowledge in the struggle to maintain agricultural productivity, as Sahelian communities confront soil fertility depletion, food insecurity, and climate change. The study finds that farming communities in this region can strengthen their livelihood resilience and enhance crop yields if they update elements of the well-adapted historic farming system, employ new techniques and tools, and in the process, forge coherent farming systems that still make cultural sense to farmers. / 10000-01-01