Dissertations / Theses on the topic 'Soils – Zimbabwe'

Includes bibliographical references (leaves 106-118).
The research focuses on an objective analysis of austral summer rainfall variability over Zimbabwe as well as characterization of rainfall patterns and frequency analysis over southern Africa region. A statistical analysis of historical trends in climate extreme events is used and lays a foundation of projecting into future climates. A trend analysis done on rainfall patterns attained from SOMs approach compliments the RClimdex statistical approach and strengthens some of the historical trends findings on climate extremes. Thereafter, some exploratory research seeks to explain the trends observed using the land-atmosphere interactions and shows the response of rainfall to anomalous soil moisture conditions during an extreme wet and dry seasons using RegCM3. Finally, some radiation effects results are presented from these soil moisture perturbations experiments. Results show drying out patterns over the region from the historical records analysed. The trend analysis done with SOM arrays revealed a positive trend towards drier conditions and a negative trend for wet conditions. The climate extremes indices analysis complimented these findings as shown in the decrease in total precipitation and an increase in the number of dry spells. This is supported by the circulation patterns showing an increase in frequency of the 500hPa anticyclones and a decrease of low pressures. However, some high altitude stations showed an intensification of precipitation events. This would exacerbate need for proper planning of future water resource management and farming strategies. Soil moisture rainfall feedback mechanisms were not fully explored. However drier conditions experiments showed a stronger response to soil moisture perturbations than in wetter conditions experiments. No consistent response to soil moisture initialisation over southern Africa was found. The altitude does modulate these feedback mechanisms with low-lying areas depicting a stronger response. A better understanding of the observed rainfall patterns, historical climate trends and soil moisture-rainfall feedback mechanisms are essential for improved short-term and seasonal forecasting and will aid the generation of plausible climate change impact predictions.

Thesis (PhD(Agric) (Agronomy))--University of Stellenbosch, 2009.
ENGLISH ABSTRACT: Continuous cropping without replenishing the nutrient component of soils will eventually lead to the depletion of soil nutrients. Small scale farmers in Zimbabwe often do not have the financial means to buy fertilizer and this problem is exacerbated by scarcity of commodities such as fertilizers. The use of herbaceous legumes such as mucuna (Mucuna pruriens) can assist to recapitalize soil fertility depletion and improve subsequent maize productivity in sandy loam soils in the small holder farming sector of Zimbabwe. In this study the effect of phosphorus (P) application to a mucuna crop, the effect of mucuna management options and the application of nitrogen (N) to the subsequent maize crop was investigated. The experiment was carried out during the 2007 to 2009 seasons at the Grasslands Research Station in Marondera in Zimbabwe. The soils are classified as humic ferrolsols and are predominantly of the kaolinitic order with sandy loams of low fertility and are slightly acid (pH CaCl = 5.2). A randomized complete block design was used for the effect of P on mucuna productivity and the effect of P and mucuna management options on the soil properties. The treatments were two P rates (P0 and P40 = 0 kg P ha-1 and 40 kg P ha-1 respectively) applied to a preceding mucuna crop, four mucuna management options [1) fallow (F) (no mucuna planted = control), 2) mucuna ploughed-in at flowering (MF), 3) all mucuna above ground biomass removed at maturity and only roots were ploughed-in (MAR) and 4) mucuna pods removed and the residues ploughed-in (MPR)]. A split-plot design was used to study the effect of P application to mucuna, mucuna management options and N rates on the growth and yield of the subsequent maize crop. The four N treatments [N0 = 0 kg N ha-1, N40 = 40 kg N ha-1, N80 = 80 kg N ha-1 and iv N120 = 120 kg N ha-1] were applied to a subsequent maize crop. Growth and development parameters such as biomass production, leaf area index, nutrient content of the foliage and grain yield were determined in the mucuna and maize crops. Soil parameters investigated included nutrient content, pH, bulk density and porosity. Phosphorus application in these particular soil conditions positively influenced mucuna biomass production and therefore enhanced the role of mucuna as a rotational crop by increased positive effects on the subsequent maize crop. The incorporation of above-ground biomass of mucuna had positive effects on all soil properties investigated. The MF and MPR management options increased the soil organic matter (OM) and reduced bulk density which leads to an improvement in porosity (f) of the soil. Mucuna incorporated at flowering (MF) and P40 treatment combination resulted in the highest mineral N, P, potassium (K), calcium (Ca) and magnesium (Mg) levels. A significant three-way interaction (P<0.05) between mucuna management options, nitrogen rates and time was observed in terms of biomass production and all nutrients in the leaves of the subsequent maize crop. The main findings were that the MF management option had the highest biomass and foliar nutrient accumulation through-out all the treatment combinations. In general the MF management option gave the highest maize yield across all the treatment combinations. Incorporation of mucuna biomass into the soil prior to planting a maize crop therefore improve soil physical and chemical qualities resulting in improved soil conditions for a subsequent maize crop which in turn lead to higher maize yields. Including a mucuna rotational crop have a similar effect on maize yield than application of 80 kg ha-1 of fertilizer N.
AFRIKAANSE OPSOMMING: Aanhoudende verbouing van gewasse op dieselfde grond sonder om voedingstowwe aan te vul lei uiteindelik tot die agteruitgang van die grond se vrugbaarheid. Kleinboere in Zimbabwe het meestal nie die finansiële vermoëns om bemestingstowwe te koop nie en die probleem word vererger deur die onbekombaarheid van kommoditeite soos bemestingstowwe. Die gebruik van kruidagtige peulplant gewasse soos mucuna (Mucuna pruriens) kan bydra om grondverarming teen te werk en om die produksie van ‗n daaropvolgende mielie aanplanting in sandleemgronde in ‗n kleinboerstelsel in Zimbabwe te verhoog. In hierdie studie is die invloed van fosfor (P) toediening aan ‗n mucuna aanplanting, die invloed van bestuursopsies van die mucuna en die toediening van stikstof (N) aan die daaropvolgende mielie aanplanting ondersoek. Die eksperiment is tydens die 2007 tot 2009 reënseisoen by die Grasslands Research Station in Marondera in Zimbabwe uitgevoer. Die grond word geklassifiseer as humiese ferrolsols en is hoofsaaklik sanderige leemgrond van die kaolinitiese orde met lae vrugbaarheid en is effens suur (pH CaCl = 5.2). ‘n Volledig ewekansige blokontwerp is gebruik om die invloed van P op die produktiwiteit van mucuna te bepaal asook die invloed van P toediening en mucuna bestuursopsies op grondeienskappe. Die behandelings was twee P vlakke (P0 = 0 kg P ha-1 en P40 = 40 kg P ha-1) wat aan ‗n voorafgaande mucuna aanplanting toegedien is, vier mucuna bestuursopsies [1) braak (F) (geen mucuna geplant = kontrole), 2) mucuna ingeploeg met blomtyd (MF), 3) alle bogrondse mucuna biomassa verwyder by rypwording en slegs wortels ingewerk (MAR) en 4) mucuna peule verwyde en die res van die bogrondse material ingeploeg (MPR)] en vier N behandelings [N0 = 0 kg N ha-1, N40 = 40 kg N ha-1, N80 = 80 kg N ha-1 en N120 = 120 kg N ha-1] toegedien aan ‗n daaropvolgende mielie aanplanting. Groei en ontwikkeling parameters soos biomassa produksie, blaaroppervlakindeks, nutriëntinhoud van die blare en graanopbrengs is in die mucuna en mielie aanplantings ondersoek. Grondeienskappe soos nutriëntinhoud, pH, bulkdigtheid en porositeit is gemeet. Fosfaat toediening aan hierdie spesifieke grondtipe het mucuna produksie positief beïnvloed en dus die rol van mucuna as rotasiegewas verbeter deur positiewe reaksies in die daaropvolgende mielie aanplanting. Die inwerk van bogrondse mucuna biomassa het al die fisiese grondeienskappe wat ondersoek is positief beïnvloed. Die MF en MPR bestuursopsies het organiese materiaal inhoud van die grond verhoog en bulkdigtheid verlaag wat lei tot verbeterde grondporeusheid (f). Mucuna wat tydens blomvorming ingewerk is (MF) lei tot die hoogste minerale N, P, kalium (K), kalsium (Ca) en magnesium (Mg) vlakke. ‗n Betekenisvolle drie-rigting interaksie (P < 0.05) tussen mucuna bestuursopsies, N vlakke en tyd is waargeneem in terme van biomassa produksie en in terme van al die nutriëntvlakke in die mielieblare wat ondersoek is. Die hoofbevindinge was dat die MF bestuursopsie die hoogste biomassa produksie en blaarnutriënt akkumulasie oor alle behandelingskombinasies tot gevolg gehad het. In die algemeen het die MF bestuursopsie die hoogste mielie-opbrengs oor alle behandelingskombinasies tot gevolg gehad. Die inwerk van mucuna materiaal in die grond voordat mielies geplant word verbeter dus fisiese en chemiese toestande in die grond wat grondtoestande verbeter vir die daaropvolgende miegewas en uiteindelik lei tot hoër mielie-oeste. Die insluiting van mucuna as ‘n rotasiegewas het diesefde effek op mielie-opbrengs as die toediening van 80 kg ha-1 N bemesting.

Soil moisture available to crops is among the main constraints on crop production by smallholder farmers in semi-arid Zimbabwe. Other restrictions, such as limited use of fertilisers and herbicides, stem primarily from socio-economic rather than biophysical constraints. To improve smallholder farming, it is essential to promote soil and water conservation practices (SWC) that consider farmers' management constraints, such as limited availability of labour and Draught Animal Power (DAP).

This thesis concerns soil erosion and conservation in Zimbabwe. It is framed in the light of the contemporary heightened concern for the environment generally in Africa and the recent publication of the National Conservation Strategy for Zimbabwe (1987). Soil erosion is an archetypal interdisciplinary problem. This thesis complements and extends understanding of soil erosion and conservation in Zimbabwe via a methodological approach and a scale of analysis which have been under-represented in the literature to date. The research adopts a pluralist, regional political ecology approach (after Blaikie and Brookfield 1987) to soil erosion and conservation in Svosve communal area, combining political-economic understanding with case study analysis of changing social-environmental relationships. Plural problem definitions are constructed through interview and survey techniques, historical analysiso f archival sourcesa nd oral testimonies,a ssessmenot f contemporary policy and planning documents and via sequential air photograph analysis. The researchc hallengesa spectso f the colonial conservationislti terature to date for southernA frica andn ational level modelling of human-environmenrte lationshipsi n Zimbabwe. It presentsa quantitativea ssessmenotf the changei n symptomso f deterioration and in the nature and extent of soil erosion for the case study area. It operationalisesth e concepto f multiple problem definitions with implications for the contemporary model for conservation extension and for improving the role of local development institutions.

This thesis utilizes three theoretical approaches; political ecology, settler culture and community conservation to examine soil conservation and the white agrarian environment in colonial Zimbabwe to evaluate to what extent players in government and the agricultural sector were conscious or concerned about preservation and conservation of the soil. The thesis also examines the role of local and international ideas in the colony’s conservationist tradition, and whether the soil conservation movement was identity-forming among the colony’s settler farmers. The history of conservation on settler farms in colonial Zimbabwe can be periodized into three broad timeframes - from the 1890s to around the mid-1930s, between 1934 and 1965 and the Unilateral Declaration of Independence (UDI) period. In the first three and half decades of the 20th century the history of conservation can best be described as being characterized by a series of “dilemmas.” The British South Africa Company (BSA Co.) administration did not pursue soil conservation in any significant, synchronized or sustained manner. In the second period, from 1934 to 1965, there was considerable progress in the construction of conservation works on settler farms. This process was the result of recommendations made by Natural Resources Commission, a body that was appointed in 1938 to investigate the status of the colony’s natural resources. The mid-1940s were characterized by the formation of Intensive Conservation Areas (ICAs) in settler farming districts whose mandate was to oversee the construction of conservation works to rehabilitate settler farms. With the support of the Natural Resources Board (NRB), and the Department of Conservation and Extension (CONEX), formed in 1948 to provide expertise on conservation-related matters and extension support, all settler farming areas were covered by trained CONEX staff, though in most instances very thinly distributed due to high demand for their service and manpower constraints in the department. The third period, the UDI era, was characterized by attempts by the minority settler government to forestall majority rule in the colony. Malawi and Zambia (formerly Nyasaland and Northern Rhodesia, respectively) had been granted their independence by Britain in 1964. As decolonization was taking place in other parts of Africa, black majority rule in colonial Zimbabwe also seemed imminent. To the alarm of the white minority government, Britain had set out to grant majority rule to its African colonies, including Southern Rhodesia (renamed Rhodesia after Zambia’s independence). The Ian Smith-led government of Rhodesia, feeling betrayed, declared UDI on 11 November 1965, delaying Zimbabwean independence by another 15 years. With the end of the Federation in 1963, the colony could no longer rely on federal resources as it had done between 1953 and 1963. Sanctions, imposed in reaction to UDI, further put the regime in a tight corner. Their impact was quite significant. Fuel had to be rationed, and general belt-tightening across the board inevitably followed as major Rhodesian exports such as tobacco and minerals were embargoed on international markets. The start of the liberation war at the end of the 1960s further complicated matters.
Thesis (DPhil)--University of Pretoria, 2013.
gm2014
Historical and Heritage Studies
Unrestricted

Thesis (MA)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: When land loses its intrinsic qualities or suffers a decline in its capabilities it is said to be degraded. Land degradation manifests itself in various forms such as deforestation, soil erosion, land, air and water pollution. In the context of sustainable development land degradation has become one of the world's major concerns. Now, more than ever before, it has become urgent to carry out empirical studies on the nature and extent of land degradation and to come up with appropriate responses to the problem. In much of the developing world communal natural resource management practices are common. It is often assumed that communal exploitation of common property resources such as woodlands, pastures, water sources and wildlife inevitably leads to land degradation. This is due to the belief that humankind would seek to derive maximum benefit from common pool resources without incurring any costs towards the conservation of those resources. This study was an environmental assessment of the impacts of communal land-use systems and common property resources management practices in the Mhondoro communal lands of Zimbabwe. The area has been subject to human settlement for over a century and is regarded as a typical representation of a well-established communal land management system. Several methods were used to make the assessment. These included the following: a questionnaire survey; interviews with key informants; soil and vegetation traverses and field measurements; tree density counts in demarcated plots; calculation of the population density and livestock density for the study area; completion of an environmental evaluation matrix and a communal projects sustainability index checklist; and analysis of geo-referenced time-lapse aerial photography covering a fifteen year period (1982-1997). It was established that serious land degradation had occurred in Chief Mashayamombe's ward in Mhondoro. Degradation manifested itself in the form of soil erosion and stream sedimentation, woodland depletion, pasture degradation and wildlife habitat destruction. Communal land-use and natural resource management practices are only partially to blame for this state of affairs. The fragile nature of the sandy soils of the uplands, the sadie soils of the vlei areas, combined with the fairly high rainfall amounts (annual average 750mm) make the area prone to soil erosion. Rainfall intensity tends to be high in the area and when the rain falls on the poorly vegetated, and highly erodible soils erosion occurs. The land has become severely stressed due to over-utilisation; a population density of 93 people per km2 and livestock density of 110 cattle per km2 were recorded. The land available for communal settlement in the area has been limited in extent. Due to the general poverty of the communal farmers the replacement of nutrients into the cultivated soil has not kept pace with the deteriorating condition of the land. Contrary to popular misconceptions, communal area residents have shown concern for environmental conservation through fallowing their fields, gully reclamation efforts, grazing schemes, woodland preservation and tree growing practices. Remedial and/or mitigatory measures for the environmental recovery of the area could adopt some of these well-established practices and incorporate them in a whole-catchment management strategy. Key words Land degradation, environmental degradation, pollution, environmental assessment, common property resources, communal land uses, sustainable resources management, sustainability indicators, soil erodibility, soil erosivity
AFRIKAANSE OPSOMMING: Wanneer grond sy intrinsieke waarde verloor of 'n afname in sy vermoë toon, kan gesê word dat die grond gedegradeer is. Gronddegradasie manifesteer in verskeie vorme, soos ontbossing, gronderosie, grond, lug en water besoedeling. Gronddegradasie het binne die konteks van volhoubare ontwikkeling wêreldwyd van besondere belang geword. Nou, meer as ooit vantevore, is dit noodsaaklik om empiriese studies uit te voer aangaande die aard en omvang van gronddegradasie, en om vorendag te kom met toepaslike reaksies tot die probleem. Gemeenskaps natuurlike hulpbron bestuur praktyke is algemeen in die ontwikkelende wêreld. Daar word dikwels veronderstel dat uitbuiting van gemeenskaplike eiendoms hulpbronne deur die gemeenskap, soos woude, weivelde, waterbronne en wild, onvermeidelik lei na gronddegradasie. Hierdie aanname het ontwikkel as gevolg van die oortuiging dat die mensdom daarna sal streef om maksimum voordeel te trek uit gemeenskaplike hulpbronne, sonder om enige koste aan te gaan ten opsigte van die bewaring daarvan. Hierdie studie behels 'n omgewings evaluering van die impakte van gemeenskaps grondgebruik sisteme en gemeenskaplike eiendoms hulpbron bestuur praktyke in die Mhondoro gemeenskaplike grond van Zimbabwe. Die area word al vir meer as 'n eeu deur mense bewoon, en word beskou as 'n tipiese voorbeeld van 'n gevestigde gemeenskaps grondbestuur sisteem. Verskeie metodes is toegepas met die evaluering, en sluit in: 'n vraelys opname; onderhoude met sleutel segspersone; grond en plantegroei opnames en veldopnames; boom digtheidstelling in afgebakende persele; berekening van bevolkingsen veedigtheid vir die studiegebied; opstelling van 'n omgewing evaluerings matriks en 'n gemeenskap projek volhoubaarheids indeks kontroleerlys; en 'n analise van geo-referenced time-lapse lugfoto's wat strek oor 'n tydperk van 15 jaar (1982-1997). Daar is vasgestel dat ernstige gronddegradasie voorkom in Hoofman Mashayamombe se wyk in Mhondoro. Degradasie word gemanifesteer in die vorm van gronderosie en stroom sedimentasie, uitputting van woude, weiveld degradasie en die verwoesting van wild habitatte. Gemeenskaps grondgebruik en natuurlike hulpbron bestuurspraktyke is net gedeeltelik verantwoordelik vir die stand van sake. Gronderosie vind plaas ook as gevolg van die sensitiewe aard van die sanderige grond van die hoogland, die sodic grond van die vlei areas, in kombinasie met redelike hoë reënval (gemiddeld 750mm per jaar). Reënval intensiteit in die area is geneig om hoog te wees, en erosie vind plaas wanneer reën val op die hoogs erodeerbare grond wat met yl plantegroei bedek is. Die grond verkeer onder geweldige druk as gevolg van oorbenutting; 'n bevolkingsdigtheid van 93 mense per km2 en veedigtheid van 110beeste per km2 is aangeteken. Die grond beskikbaar vir vestiging van gemeenskappe word in omvang beperk. Die vervanging van grondvoedingstowwe in bewerkte grond hou nie tred met die agteruitgang in die kondisie van die grond nie, as gevolg van die algemene armoede van die gemeenskapsboere. Inwoners van die gemeenskapsarea , teenstrydig met algemene wanopvattings, toon besorgdheid ten opsigte van omgewingsbewaring deur die grond braak te lê, donga herwinnings pogings, wei velds planne, bewaring van woude en praktyke ten opsigte van die groei van bome. Remediërende en/of versagtende maatstawwe vir die herstel van die omgewing kan van hierdie gevestigde praktyke inkorporeer in 'n bestuursstrategie wat die hele opvangsgebied insluit. Sleutelwoorde Gronddegradasi e, omgewingsde gradasi e, besoedeling, omgewingsassessering, gemeenskaplike eiendoms hulpbronne, gemeenskaplike grondgebruik, volhoubare hulpbron bestuur, volhoubaarheids aanwysers, grond erodeerbaarheid, grond verwering.

This thesis is a qualitative ethnographic study of innovations implemented by Mr Zephaniah Phiri Maseko, a smallholder farmer from Zvishavane, rural Zimbabwe. Ethnographic data provides insight and lessons of his practices for rethinking existing strategies for adaptation to climate change. The concept of adaptation is probed i n relationship to the closely related concepts of vulnerability, resilience and innovation. This study also explores the concept of conviviality and argues that Mr Phiri Maseko's adaptation to climate hinges on mediating barriers between local and exogenous knowledge systems. Ethnographic fieldwork aided by an analytical framework of resilience makes clear that his farming practices are informed by a realisation that dualisms are problematic. His innovations are a way of building resilience to climate change and his practices demonstrate the interdependencies in a socio - ecological system. This study argues that innovations by smallholders play a complementary role to interventions by outsiders in the discourse of adaptation to climate in the drylands of southern Zimbabwe. Mr Phiri Maseko harvested water as a way of adapting to climate variability. I argue that he offered tangible adaptive climate strategies through his innovations that "marry water and soil so that it won't elope and run - off but raise a family" on his plot. His agricultural practices are anchored on the Shona concept of hurudza (an exceptionally productive farmer). This thesis explores the concept and practices of uhurudza , to suggest that the latter - day hurudza (commercial farmer) as embodied by Mr Phiri Maseko offered an important set of resources for the development of climate adaptation strategies in the region. Therefore, his activities call for a revisit of the notion of hurudza based on grain harvested, one that includes consistent income generated from selling farm produce. His innovations demonstrate elements of conviviality, resilience, accommodating local knowledge as well as ideas he learnt from various educational institutions in order to adapt to climate variability. This thesis explores the usefulness of Mr Phiri Maseko's innovations for other smallholder farmers in the Zvishavane area who have replicated it. I demonstrate that due to the success of his innovations, uptake has been high underpinning the fact that these smallholders appear to be managing to adapt to climate variability. This ethnographic study of smallholder farmers' adoption of innovations to climate highlights the "complex interplay" of multiple factors that act as barriers to uptake. Such interplay of multiple stressors increases the vulnerability of smallholders. I conclude by arguing that in as much as the skewed colonial land policy impoverished the smallholder farmers, Mr Phiri Maseko nonetheless redefined himself as a latter - day hurudza and thus breaks free from the poverty cycle by 'conjuring ingenious' ways of reducing vulnerability to climate. I do not suggest that his innovations offer a 'silver bullet' solution to the insecure rural livelihoods of smallholder farmers; nevertheless, they are a source of hope in an environment of uncertainty.

The effects of artificially supplied perennial water on soil properties, vegetation dynamics and the distribution of large herbivores was investigated in southeastern Zimbabwe. Data collection took place between March 1997 and July 1998. Water points were situated primarily on three different soil types (clay-loam, sandy-clay-loam and sand), and in four different vegetation types (Hill communities, Colophospermum mopane veld, Acacia nigrescens woodland and Albizia petersiana woodland). One water point in C. mopane veld (Bandama) had been closed two years prior to data collection, while another, in the Hill community (Manyoka), had been introduced, two years prior to data collection. Changes in physical (infiltration) and chemical (organic carbon and nutrients) properties of soils around water points were largely restricted to within 100 m of water. Chemical enrichment of the soil occurred only at water points that had been in place for more than two years. Soil surface conditions were altered to distances beyond 100 m from water. Manyoka (the new water point) was an exception, with extreme changes limited to within 100 m of water. Herbaceous and woody species composition changed in response to distance from water with changes best described by asymptotic equations. Changes in species composition of the woody component appeared to be longer lasting than changes to the herbaceous component. Most perennial grass species declined close to water, but Urochloa mosambicensis increased close to water in areas outside of the Hills. Herbaceous species diversity was adversely affected by distance from water on sandy soils (Hill communities and A. petersiana woodland), but was largely unaffected on clay-loam (A. nigrescens woodland) and sandy-clay-loam soils (C. mopane veld). Woody species composition and density was altered out to 500 m from perennial water in Acacia nigrescens woodland on clay-loam soils. Results suggest that this vegetation type may be susceptible to bush encroachment close to water. Trends in woody canopy utilisation were generally similar to trends in woody species composition, and it is proposed that the former may be used to indicate future changes in the latter. Conversion of trees to shrubs was highest at Manyoka (the new water point) indicating that woody destruction by elephants is extreme during the initial years following water introduction. Large herbivore biomass was greatest close to water (< 1 km) during the dry season but not during the wet season. Herbivore species distributions appeared to be influenced by the position of perennial water, but since all range was within easy access of water, it is unlikely that animal distributions were constrained directly by the position of surface water. It is more likely that herbivores were spatially separated on the basis of habitat type.
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1999.

Microbial biodegradation methods of hydrocarbon contaminated soils that can occur through biodegradation, bio augmentation, bio stimulation, and phytoremediation, have gained significant interest in recent years when compared to the conventional methods. The study was designed to explore the influence of petroleum hydrocarbon contamination on physicochemical and microbial characteristics of soils as well as determining the possibility of hydrocarbon biodegradation using biostimulation. The process involved soil characterisation and modification of nitrogen and phosphorus content to stimulate naturally adapting microorganisms. Characterisation process determined that hydrocarbon contamination of Murowa soils introduced hydrophobicity to the naturally wettable sandy loam soils. Naturally adapting microbial species capable of degrading hydrocarbons identified using Direct microscopy, Gram and Melzer’s iodine staining included Pseudomonas, Bacillus, Serratia marcescens, Flavobacterium, Micrococcus, Streptomyces Staphylococcus, Penicillium and yeasts. The N: P nutrient ratio and moisture levels were identified as potential limiting factors and hence experiments focused on manipulation of N: P nutrients to stimulate the identified hydrocarbon degrading organisms (bio stimulation). Hydrocarbons were identified by solvent extraction using hexane and gas chromatography. These included decane, undecane, hexadecanal, 2-ethylcridine, octadecane and 1-iodo. Soils weighing 10kgs with hydrocarbons levels of about 265mg/kg were subjected to eight (8) treatments with seven (7) different combinations of N (6000-12000mgN): P (600- 3000mgP) concentration ranges including the control. Nitrogen The moisture was adjusted and tilling for aeration was done on a weekly basis. Changes in Total Petroleum Hydrocarbon (TPH), C: N: P ratio, microbial mass and pH were evaluated over 111 consecutive days. The optimum N:P ratio was the determined to 2:1 molar ratio in form of 6000mgN:3000mgP. TPH concentration was reduced by 73% from the initial concentration within the first 74 days. Beyond 74 days there were no significant changes in the TPH concentration and this was attributed to the presence of more complex insoluble hydrocarbons which needed more time and an additional bio surfactant to complete mineralization. The conclusion was that a combination of natural attenuation and biostimulation methods can be used to bioremediate Murowa hydrocarbon contaminated soils using the 2:1 molar ratio of what
College of Agriculture and Environmental Sciences
M. Sc. (Environmental Science)

The effects of irrigation-induced salinity and/or sodicity on sugarcane yield, and two growth parameters, namely stalk height and number of nodes per stalk , were investigated on a sugarcane estate in the Zimbabwean lowveld. The effects of soil salinity and/or sodicity on the size, activity and metabolic efficiency of the soil microbial community was also studied. Furrow-irrigated fields which had a gradient in soil salinity and/or sodicity which increased from the upper to lower ends of the fields were selected for this study. This gradient was recognized by decreasing sugarcane growth down from the upper to the lower ends and the appearance of salt on the soil surface at the lower ends of fields. Sugarcane growth was classified as either dead, poor, satisfactory or good; and soil samples (0-0 .15 m, 0.15-0 .3 m, 0.3-0 .6 m and 0.6-0.9 m) were taken from each of these areas. Soils from under adjacent areas of undisturbed veld were also sampled. Sugarcane growth and yields in micro-plots of the various areas of the fields were measured. Foliar samples of sugarcane were taken at 22 weeks of age and analysed for nutrient content. Soil salinity and sodicity were quantified by measuring pH(water), electrical conductivity (ECe) and cation content of saturation paste extracts and the exchangeable cation content. From this information, the sodium adsorption ratio (SARe)and exchangeable sodium percentage (ESP) were also calculated. The calcareous, vertic soils in the study area under undisturbed veld were found to have high pH values (8 to 9.5), very high exchangeable Ca and Mg concentrations and there was evidence of accumulation of soluble salts in the surface 0.15 m. Under sugarcane production, irrigation induced salinity and sodicity had developed. Under poor and dead sugarcane, high values for ECe, SARe, and ESP were generally encountered in the surface 0-0 .3 m of the profile. In addition, the pH values under sugarcane were often between 9 and 10 particularly in profiles where sugarcane grew poorly or had died. As expected, pH was positively related to ESP and SARe, but negatively related to ECe. Measurements of aggregate stability by wet sieving, the Emerson dispersion test and the Loveday dispersion score all showed that soils from the study sited tended to disperse and that dispersion was most apparent where high ESP and SARe values occurred in association with elevated pH values and relatively low ECe values. These measurements confirmed observations at the sites of low infiltration rates and restricted drainage particularly on the lower ends of fields where sugarcane had died. In addition to the above measurements it was also observed that there was a rise in the watertable under furrow irrigation and that the watertable was nearest to the surface at the lower ends of the fields. In some cases the watertable was observed to be only 0.2 to 0.3 m from the surface. Thus, death of roots due to anaerobic conditions could be occurring to a greater extent at the lower ends of the fields. Another consequence of the high watertable was that these vertic soils were observed to remain in a permanently swollen state. This limits air and water movement in the soil profile as such soils need to be allowed to dry out and crack regularly so that macroporosity can be restored. Sugarcane yield, stalk height and number of nodes per stalk were not significantly related to ECe. Sugarcane yields were, however, significantly correlated with ESP and pH while stalk height and number of nodes were negatively correlated with ESP, SARe and pH. These results suggested that sodicity was a more limiting factor for sugarcane growth than salinity. Foliar analysis of leaf tissue did not reveal substantial differences in macro- or micro-nutrient content between good and poorly-growing sugarcane. It was concluded that the gradient of decreasing sugarcane growth down the furrow-irrigated fields, with crop death at the lower ends, was the result of a combination of factors. That is, the watertable had risen due to over-irrigation and it was nearer the surface at the lower ends of the fields. Due to capillary rise of salts, this resulted in sodic and sometimes saline-sodic conditions in the surface soil. These conditions could limit plant growth through ion toxicities, plant water stress and inhibition of root growth and function and physiological processes. These would be induced by the high pH and high salt, Na and HC03- concentrations in soil solution. Poor physical conditions associated with sodicity and the continually swollen state of the soils presumably limited infiltration and aeration in the surface soil, and probably restricted root growth. In addition, it is likely that the high watertable limited effective crop rooting depth to about 0.2 m at the lower ends of the fields. The net result was that sugarcane died at the lower ends. A negative effect of soil salinity and/or sodicity was also observed on the soil microbial population. Significant negative correlations were obtained with ECe SARe and ESP with microbial biomass C and microbial activity (as measured by FDA hydrolytic activity or arginine ammonification rate). The activity of enzymes involved in C (P-glucosidase), P (phosphatase) and S (arylsulfatase) mineralization and potential nitrogen mineralization (as determined by aerobic incubation) were also negatively correlated with these factors, with the exception of arylsulfatase activity and ESP. All the above mentioned microbial population measures were also positively correlated with soil organic C content, besides potential nitrogen mineralization. The metabolic quotient, which provides an indication of stress and efficiency of the microbial community, increased considerably with increasing salinity and sodicity and decreased with soil organic C. Thus, increasing salinity and/or sodicity resulted in a smaller, more stressed, less efficient microbial community, while the turnover rate and cycling of C, N, P and S also decreased. It was concluded that salt affected soil not only causes a decline in sugarcane yield through raising the concentration of soluble salts in soil solution, but also has a detrimental effect on microbial activity and on mineralization of soil organic C, N, Sand P.
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.

Although soils developed from ultramafic parent materials have significance to agriculture, ecology and health, their bio-geochemistry is poorly understood. The mineralogical and bio-geochemistry of soils formed from the ultramafic parent materials of the Great Dyke, Zimbabwe and Gillespie County, Texas was investigated. The objectives were to determine the mineralogical and bio-geochemical properties of the soils in order to assess the potential impact and challenges to agriculture, and environmental quality. Soil samples were taken from the crest, shoulder, footslope and the toeslope. Chemical analyses were performed by nuclear and spectroscopic techniques. Mineral characterization was conducted by x-ray diffraction (XRD) and spectroscopic techniques. Microbial whole-community structure was determined by the fatty acid methyl esters (FAME) technique. The results indicate wide chemical and mineralogical compositions among the studied sites. The soils contain relatively high concentrations of heavy metals (some sites contain Cr(VI)), but low levels of K and Ca. The highest concentrations of trace metal were associated with chromite, Fe oxides and serpentinite. The concentrations of Mg were higher than those of Ca and varied between Zimbabwe and Texas soils largely due to the parent materials. Unique to these soils is the occurrence of talc, serpentine, chlorite, Fe-rich smectite, amphiboles, pyroxenes, Fe and Cr oxides in relatively large amounts. These soils also lack micas and have neglible amounts of kaolinite and feldspars. Palygorskite and serpentine occurred in specific soil horizons and at specific landscape positions. FAME profiles indicate that the soil microbial community structure is predominantly bacteria and fungi (including arbuscular mycorrhiza fungi) at each landscape position across the transect. Biomarkers for actinomycetes were undetectable. The proportions of Gram-positive bacteria were higher than those of the Gram-negative bacteria. Very low levels of nutrients (Ca and K), higher Mg/Ca molar ratios, and the relatively high concentrations of heavy metals in these soils impact agricultural productivity. High concentrations of heavy metals, the presence of the Cr(VI) as well as its great potential to form in these soils might impact microbial activity and environmental quality. The occurrence of fibrous minerals (e.g serpentine and amphiboles) in these soils will likely impact human health.

Landfills have served as the major sites for waste disposal in both developed and developing countries. Upon closure of a landfill site, the surface could be converted to a golf course, recreation park, playground, animal refuge, tennis court and industrial site. Even when closed, landfills still have the potential to contaminate the surrounding environment as a result of the migration of leachate from decomposing waste contained in the site. This study focused on assessing the impacts of a closed landfill on soils and plants at Lumberstewart closed landfill site in Bulawayo, Zimbabwe. Soil samples were collected at three different depths (0-30 cm, 30 - 60 cm and 60-90 cm) at the landfill and a control site. The soil samples were analysed for their texture, pH, electrical conductivity, organic matter content, cation exchange capacity and concentrations of Cd, Cu, Cr, Fe, Ni and Zn. Samples of jimson weed and pigweed growing at the closed landfill and the control site were collected from the same sites where soil samples were collected, and the concentrations of the same set of heavy metals in these weeds determined. Soil samples were digested using EPA method 3050B: Acid Digestion of Sediments, Sludge and soils whereas nitric acid and hydrogen peroxide was used for digestion of plant samples. Both plant and soil digests were analyzed for heavy metals concentrations using Flame Atomic Absorption Spectrometry (AAS). Soils from the landfill as well as the control site had a high content of sand with soil pH values which were alkaline. The electrical conductivity values of the soil samples were relatively low ranging from 0.39 to 1.67 dS/m, indicating low levels of salts in soils at the landfill. The concentrations of heavy metals at the closed landfill site were higher than the control site. Heavy metals concentrations in soils at the closed landfill followed the order Fe>Zn>Cu>Cr>Ni>Cd. Results indicated that Fe was exceptionally higher than the other metals with concentration values averaging 45690±17255 mg/kg. Cadmium on the other hand had the least concentration with values of 0.01±0.00 mg/kg. Values of Enrichment Factors of heavy metals around the soil at different depths indicated that the enrichment of heavy metals increased with depth at the landfill up to 30-60 cm after which a decrease was observed. Values for heavy metal Contamination Factor of soils around the landfill ranged from low concentration (CF<1) to very high concentration (CF>6). The Pollution Load Index (PLI) values for the soil at the Lumberstewart landfill indicated that all sites were polluted (PLI>1). Site 6 had significantly higher mean concentration of heavy metals in soils at the landfill whereas site 11 had the least. The concentrations of Cd and Ni in soils at the landfill were below permissible limits of South African National Norms and Standards (NNS) as prescribed by NEMA (2008) in South Africa whereas Cr, Cu and Zn in soils were above the NNS permissible limits. Heavy metal concentrations in soils at the landfill were above World Health (WHO) permissible limits except for Cd which was equal (0.01 mg/kg) to the permissible values of Cd in the soils at sites 5, 8, 9, 10, 11 and 12. Mean concentrations of heavy metals in jimson weed and pigweed were in the order Fe>Zn>Cu>Cr>Ni>Cd. The concentrations of Cd, Cr, Cu, Fe and Zn in both plants from all sites at the landfill were significantly higher than the control site. Heavy metal transfer coefficient for both plants indicated that heavy metal uptake was more species dependent than soil heavy metal concentration dependent. The results from this research indicate that though the Lumberstewart Landfill has been closed, it is still affecting the soils in the vicinity of the landfill. Plants and water around the Lumberstewart closed landfill could be at risk from heavy metal contamination. High concentrations of heavy metals observed in the soil could present a health risk to communities should they decide to use the landfill site for arable purposes.
Environmental Sciences
M. Sc. (Environmental Science)

This qualitative study focuses on two questions: a) Do present-day Shona still subscribe to the world-view of their ancestors? b) How does this world-view relate to that of the modern (Western) world? Interviews were conducted with government representatives, chiefs in Masvingo Province and people in all walks of life. Virtually all interviewees, even when participating in the "modern" sector (including Christianity), still subscribe to the traditional system. Government, however, has adopted the model of the pre-Independence government, with some concessions to tradition. The traditional world-view (emphasising its key symbols, blood and soil) and the history of the two dominant tribes in Masvingo Province are outlined. A case study of a current chieftaincy dispute illustrates the dilemma. Conclusion: searching dialogue between the two belief systems is needed to resolve the potentially creative ambivalence. Some key issues are suggested as starting points for such dialogue.
M.A. (Religious Studies)