Thesis (MScAgric)--University of Stellenbosch, 2000 / ENGLISH ABSTRACT: Approximately 7000 ha of potatoes are cultivated under irrigation. The greatest part of the planting is entered under the South African Certification Scheme as seed potatoes, representing between 35 and 40 % of seed production in South Africa. The production of high-quality tubers is, therefore, in the interest of the entire country. Some production factors in the area, however, have a very negative influence on quality with a resultant increase in input costs. These factors include mainly low clay content of the soil «5 %), low organic matter content (% C = 0,2 to 0,4 %), a low pH value as well as a high level of chlorides (400 mg.kg") in the irrigation water. Nitrogen conversion as well as uptake can be influenced by these factors. There may also be negative influences on the environment if leaching of nitrates to subterranean water sources is involved, which can pose a threat to sensitive protected areas. Leaching of various nutritional elements occurs as a result of the low clay content of the soils. Over-irrigation or intense thundershowers could lead to the leaching of nearly all of the fertilisers from these soils. Various management aids are therefore needed to facilitate the decision-making process for corrective steps. Soil, leaf or total-plant analyses are possible, but it is a time-consuming process and the results could become available too late to be of any use. Consequently, the development of methods to determine the nutritional element status of plants on the land and the establishment of norms are both essential. A method which has been tried on a wide scale with varying results is the use of the nitrate content of the petiole, which is determined by means of a reflectoquant and nitrate strips. To evaluate the sensitivity of the method two sites in the Sandveld have been selected. A trial planting has been established at Wadrift and information was also obtained from a leaching trial at Sandberg. The cultivars Up-to-Date and Hertha were established in four nitrogen treatments (100, 200, 300 and 400 kg N.ha-1 ), and repeated over two seasons. At Sandberg irrigation was applied at three application levels and three fertigation divisions for one season. Drip irrigation was applied in both cases to enable the accurate distribution of water and fertilisers during the planting season. Petiole samples were taken weekly or every second week in all the trials. The first mature leaf was sampled (about 20 to 30 leaves per plot). During the initial planting at Wadrift nitrate N in petiole sap (measured by means of nitrate strips and a reflectoquant) was compared to nitrate N of dried petioles measured with an auto-analyser. In all test cases a good correlation was found. The readings from the auto-analyser were about 14.5 times higher than the readings from the petiole sap as a result of moisture loss during the drying process. A better correlation was obtained during the second season when the petiole sap was used for strips as well as the auto-analyser. The petiole nitrate content was increased by high N application rates and the 400 kg N.ha-1 treatment showed significant differences from the other N treatments. A substantially higher yield was obtained during the last season. Varying results were obtained regarding specific gravity for cultivars and nitrogen treatments. At Sandberg (1998) over-irrigation lowered the nitrate content of the petiole sap significantly. It was found that the optimum irrigation level and frequency, is two fertigations a week and kept at field water capacity. From the trial it was clear that the use of nitrogen strips in combination with the reflectoquant gave a good indication of the nitrate-N content of the petiole sap. It is, however, difficult to lay down a norm or critical range, as conditions during the growth period on sandy soil as well as the growth stage have a significant influence on the nitrate-No If yield is the only objective the 400 kg N.ha-1 curve can probably be used as an optimum nitrate-N norm for the particular cultivars. It is also not clear whether the nitrate N content of the petiole sap gives a good reflection of growth and yield potential. / AFRIKAANSE OPSOMMING: In die Sandveld word bykans 7000ha aartappels onder besproeiing verbou. Die grootste deel van die aanplanting word as saadaartappels onder die Suid-Afrikaanse sertifiseringskema ingeskryf en verteenwoordig tussen 35 en 40% van Suid Afrika se saadproduksie. Die produksie van hoë kwaliteit knolle is dus van landsbelang. Somminge produksiefaktore van die area het egter 'n uiters negatiewe invloed op kwaliteit en het 'n meegaande verhoging van insetkostes tot gevolg. Faktore wat veral hieronder tel is die grond se lae klei inhoud «5%), lae organiese materiaal inhoud (%C = 0.2 tot 0.4%), lae pH asook hoë chloriede (400mg.kg-1 ) in die besproeiingswater. Hierdie faktore kan 'n invloed op die omsetting van stikstof en die opname daarvan hê. Daarmee saam kan dit 'n negatiewe effek op die omgewing hê indien loging van nitrate na ondergrondse waterbronne plaasvind wat sensitiewe bewaarareas kan bedreig. Weens die lae klei-inhoud van die gronde vind loging van verskeie voedingselemente plaas. Oorbesproeiing of hewige reënbuie kan tot gevolg hê dat bykans alle bemestingstowwe uit hierdie grond geloog word. Bestuurshulpmiddels is dus nodig om die besluitnemingsproses vir korrektiewe stappe te vergemaklik. Grond-, blaar- of hele plantontledings is moontlik maar is tydrowend en resultate daarvan kan soms te laat beskikbaar wees. Die ontwikkeling van metodes om die voedingselement inhoud van plante op die land te bepaal en die daarstelling van normes is dus noodsaaklik. 'n Metode wat reeds wyd deur ander navorsers met wisselende resultate beproef is, is die gebruik van nitraat inhoud van die petiool wat met 'n reflektoquant en nitraat strokies bepaal is. Om die sensitiwiteit van die metode te evalueer is twee proefpersele in die Sandveld gebruik. 'n Proef is by Wadrift geplant terwyl data ook van 'n logingsproef te Sandberg verkry is. By Wadrift is die kultivars Up-to-Date en Hertha by 4 N-behandelings (100, 200,300 en 400 kg N.ha-1) en vier herhalings vir twee seisoene aangeplant. By Sandberg is besproeiings teen drie toedingspeile met 3 sproeibemestingsverdelings vir een seisoen gedoen. In alle gevalle is van drupbesproeiing gebruik gemaak om akkurate plasing van water en bemestingstowwe oor die plantseisoen moontlik te maak. Petiool monsters is weekliks of tweeweekliks van alle behandelings geneem. Die eerste volwasse blaar is gemonster en daar is tussen 20 en 30 blare per perseel geneem. Tydens die eerste planting te Wadrift is nitraat-N in petioolsap, gemeet met nitraatstrokies en reflektoquant, vergelyk met nitraat-N van gedroogde petiole, gemeet met In outo-analiseerder. Hierdie waardes was goed gekorreleerd vir alle gevalle wat getoets is. Die outo-analiseerder se lesing was ±14.5 keer hoër as die petioolsap lesings weens die vog wat tydens droging verwyder is. Tydens die tweede seisoen is In beter korrelasie verkry waar petioolsap vir strokies asook vir die outo-analiseerder gebruik is. Petiool nitraat is deur hoë Ntoedieningspeile verhoog en die 400 kg N.ha-I behandeling het betekenisvol van die ander N-behandelings verskil en die laaste seisoen ook In betekenisvol hoër opbrengs gelewer. Wisselende resultate is t.o.v. soortlike gewig vir kultivars en stikstofbehandelings verkry. By Sandberg (1998) is gevind dat oorbesproeiing In betekenisvolle verlagende effek op die nitraat-N inhoud in die petioolsap het. Daar is getoon dat die optimum besproeiingspeil en frekwensie, veldwaterkapasiteit met twee sproeibemestings per week is. Uit die ondersoek is dit duidelik dat die nitraatstrokies in kombinasie met die reflektoquant In uiters bruikbare aanduiding van die nitraat-N in die petioolsap gee. Dit is egter moeilik om In norm of kritiese nitraat-N grens aan te dui, aangesien toestande tydens die groeiperiode op sandgrond en die groeistadium In beduidende effek op die nitraat-N het. Indien opbrengs as enigste doelwit gestel word, mag die 400 kg N.ha-I kurwe moontlik as aanduiding van 'n optimum nitraat-N norm vir die betrokke kultivars dien. Daar bestaan ook onduidelikheid of nitraat-N in die petioolsap wel In goeie refleksie van groei en opbrengspotensiaal is.

Please read the abstract in the section 00front of this document / Dissertation (MSc Wildlife Management)--University of Pretoria, 2006. / Animal and Wildlife Sciences / unrestricted

The first recorded outbreak of nephrotoxicosis induced by the shrub Nolletia gariepina is reported. The outbreaks occurred in cattle in the Kalahari sandveld of South Africa. The toxicosis was experimentally reproduced, initially in a steer, as a pilot trial to confirm toxicity of the plant material, and thereafter in two other cattle. Toxicity was induced by intraruminal administration of 3 g/kg dried, milled plant material as a single dose. The animals had to be starved for 24 hours before dosing, as dosing on a full rumen did not induce any signs of toxicity during five days of observation and clinical pathology monitoring. In both the field outbreaks and the experimental toxicological trial, clinical signs were not specific and varied according to the duration (acute versus subacute) of the toxicological process. Clinical pathological parameters in the experimental cases indicated renal and, to a lesser extent, hepatic damage, with raised serum concentrations of urea, creatinine, aspartate aminotransferase (AST) and gamma glutamyl transferase (GGT). Increased urinary sodium and potassium concentration and GGT activity, as well as proteinuria, were evident. The histological and electron microscopical examinations revealed acute renal tubular epithelial cell degeneration and necrosis, especially of the proximal convoluted tubules. Mild hepatocellular degeneration was also noticeable. / Dissertation (MMedVet (Pathology))--University of Pretoria, 2004. / Paraclinical Sciences / unrestricted

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A land cover classification showing the landscape structure of a given area is necessary to make appropriate measures for environmental planning. The environmental impacts from insensitive human activities have led to a severe loss of biodiversity in the Cape Floristic Region over time. The natural biodiversity of the North-West Sandveld in particular, has suffered severe loss and a high level of fragmentation. The rapid growth of certain agricultural practices in the Sandveld has led not only to loss of biodiversity, but the secondary effects of excessive water extraction, invasive alien fauna and flora species and harmful run-off from toxic herbicides and pesticides. To plan effectively, an accurate map of a suitable resolution needs to be created to effectively display spatial information. The primary aim was to demonstrate that a semi-automated fine-scale, land cover classification using object-oriented image analysis is possible for a large local area to examine the environmental issues pertaining to the Sandveld. Towards this aim, a model to classify land cover of the study area was developed and its effectiveness analysed and interpreted. To meet these requirements, pre-processed SPOT 5 satellite imagery was used to digitize certain classes and to generate frame, border and Normalized Differentiation Vegetation Index (NDVI) layers for the object-oriented classification in eCognition. The accuracy of the results was determined using the Kappa coefficient which gave an accuracy level of 70%. The environmental impacts were determined after area calculations were done on each class. The results showed that the natural areas still made up the greatest percentage of the Sandveld but that it is highly fragmented, especially along the coast and many areas, although left in a natural state, were being overgrazed by livestock. The temporary irrigated, temporary non-irrigated strip agriculture and permanent agriculture classes made up the most of the remainder of the areas and had the largest impact on the Sandveld‟s biodiversity. For the biodiversity of the Sandveld to remain intact, a balance between enforcing the law and encouraging inhabitants of the Sandveld to encourage more environmentally balanced practices needs to be created. Stewardship programmes and education will greatly enhance the effectiveness of any conservation efforts. / AFRIKAANSE OPSOMMING:'n Landbedekkingsklassifikasie wat die landskapstruktuur van 'n gegewe gebied aandui, is noodsaaklik om gepaste omgewingsbeplanning toe te pas. Die effek van intensiewe menslike aktiwiteite op die omgewing oor 'n lang tydperk, het gelei tot die verlies van biodiversiteit in die Kaapse Blommestreek. Die natuurlike biodiversiteit van veral die Noordwes Sandveld is deur ernstige verliese, asook 'n vlak van fragmentasie beïnvloed. Behalwe dat die vinnige toename van sekere landboupraktyke in die Sandveld gelei het tot die verlies van biodiversiteit. Sekondêre faktore soos die oormatige water-ontrekking, indringerspesies van fauna en flora en die afloop van skadelike onkruiddoder en pes-weerende middels in rivierstelsels is ook verantwoordelik vir verlies van biodiversiteit. Om effektiewe beplanning moontlik te maak, is die skepping van 'n akkurate kaart met 'n geskikte resolusie wat die ruimtelike inligting effektief voorstel, nodig. Die hoof doel van hierdie studie was om 'n semi-geoutomatiseerde fynskaal landbedekkingsklassifikasie in 'n groot plaaslike gebied wat die omgewingskwessies rakende die Sandveld te bestudeer en demonstreer, deur gebruik te maak van objek-gerigte beeldanalise. Die effektiwiteit van 'n model wat ontwikkel is om die studiegebied te klassifiseer, was ontleed en geïnterpreteer. Om hierdie vereistes te bevredig, is voorverwerkte SPOT 5 satellietbeelde gebruik om sekere klasse te versyfer, asook om raam-, grens- en genormaliseerde plantegroei differensiasie indekslae vir beeldgerigte klassifikasie in eCognition te skep. Die akkuraatheid van die resultate was bepaal deur die Kappa-koëffisiënt wat 'n akkuraatheidsvlak van 70% gelewer het. Die omgewingsimpakte was bepaal deur opperlakteberekeninge vir elke klas te maak. Die resultate dui aan dat natuurlike gebiede steeds die grootste persentasie van die Sandveld beslaan, maar dat dit hoogs gefragmenteerd is, veral langs die kuslyn en dat baie gebiede, wat wel steeds in 'n natuurlike toestand is, oorbewei word deur vee. Die tydelike spilpuntbesproeide landbougebiede, tydelike nie-besproeide strooklandbou en permanente landbouklasse, beslaan die meeste van die oorblywende landbedekking van die Sandveld. Hierdie klasse het ook die grootste impak op die studiegebied se biodiversiteit. Om die biodiversiteit van die Sandveld te behou, moet 'n balans tussen die afdwing van wetgewing en die aanmoedig van meer omgewingsgebalanseerde praktyke in die Sandveld gevind word. Rentmeesterskap programme en opvoeding sal die effektiwiteit van enige bewaringspogings aansienlik verbeter.

Thesis (MA (Geography and Environmental Studies))--University of Stellenbosch, 2009. / Agricultural production has become vital to the Sandveld, of which Verlorenvlei is a part, in terms of both economic growth and food security. It is well documented as an area under threat of severe natural resource depletion if it is not well managed with sustainability in mind. Agricultural production, other human-driven development and the survival of the local ecosystems compete for the limited water resources. This study uses the SWAT hydrological model to simulate the transport of water through the catchment area. ArcSWAT, a third-party software extension to ArcGIS, is used as an interface between ArcGIS and the SWAT model. Spatial data (DEM, soil and landuse) is used in the preprocessing phase and fed into the SWAT model through the interface. Daily climate data were sourced and prepared according to the SWAT model’s input requirements. Considerable effort was required to fill temporal and spatial gaps in available climate data, and to infer certain unmeasured climate variables from other measurements (e.g. infer solar radiation from daylight hours, time of the year and latitude). The SWAT hydrological model was then run. The model results compared favourably to measured flow data. The study recommends building on from this first step using the SWAT hydrological model to simulate future land use scenarios for the catchment area.

Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: Water resources in South Africa are limited and groundwater plays an important role in supporting basic human needs, sustaining ecosystems and enabling industrial and agricultural development. Sound management practices are necessary to ensure sustainable development of water resources. All groundwater usage must be licensed in compliance with the National Water Act of 1998. A Spatial Decision Support System (SDSS) can be used to assist in the groundwater usage licensing process of the Department of Water Affairs and Forestry (DWAF). The main aim of this study was to develop a SDSS, named Groundwater Abstraction & Licence Evaluation Tool (GALET), that could assist in the process of allocating water use licences and determining the local impact of abstraction, based on existing theory and data. The development was done within ArcView 3.2 using the scripting language Avenue. The Sandveld, an arid stretch of land along the west coast of South Africa that is heavily impacted by groundwater abstraction, was the chosen study area. The data collected for this study included existing borehole, recharge, rainfall and geological information. GALET proved to be capable of calculating essential information needed to evaluate groundwater abstraction, which included drawdown in the water table, zone of influence and the possible effects on features such as rivers and wetlands. Targeted potential users regarded GALET as a useful tool in the process of licensing and groundwater abstraction impact assessment and plans are under way to implement GALET or a derivative thereof at the DWAF regional offices. / AFRIKAANSE OPSOMMING: Waterhulpbronne in Suid-Afrika is beperk en grondwater speel 'n belangrike rol in die ondersteuning van basiese menslike behoeftes, volhouding van ekosisteme asook industriële en landbou-ontwikkeling. Betroubare bestuurspraktyke is noodsaaklik om die volhoubare ontwikkeling van waterhulpbronne te verseker. Alle grondwatergebruik moet volgens die Nasionale Waterwet van 1998 gelisensieer word. 'n Ruimtelike Besluitnemings Ondersteuning Stelsel (RBOS) kan as 'n hulpmiddel gebruik word in die lisensiëringsproses van die Departement van Waterwese en Bosbou. Die hoofdoel van hierdie studie was om 'n RBOS, genoem Groundwater Abstraction & Licence Evaluation Tool (GALET), te ontwikkel wat as hulpmiddel gebruik kan word in die allokeringsproses van watergebruiklisensies en die bepaling van die impak van grondwateronttrekking op die omgewing, gebaseer op bestaande teorie en data. Die ontwikkeling is in ArcView 3.2 met die programmeringstaal Avenue gedoen. Die Sandveld, 'n ariede streek aan die weskus van Suid-Afrika wat onderhewig is aan grootskaalse grondwateronttrekking, is gekies as die studie area. Die data wat vir hierdie studie ingesamel is sluit bestaande boorgat, grondwateraanvulling, reënval en geologiese inligting in. GALET was in staat om belangrike inligting aangaande die evaluering van grondwateronttrekking te bereken, o.a. die daling van die grondwatervlak, die impaksone en die moontlike effekte op landvorms soos riviere en vleilande. Die teikengroep potensiële gebruikers het GALET as 'n nuttige hulpmiddel in die proses van lisensiëring en grondwateronttrekking impakbepaling beskou en planne is onderweg om dit of 'n aangepaste program by die streekskantore van die Departement van Waterwese en Bosbou te implementeer.

Thesis (MSc)--University of Stellenbosch, 2004 / ENGLISH ABSTRACT: The Sandveld, a potato growing area of the Western Cape is subject to significant groundwater abstraction for both municipal and agriculture purposes. The climate is arid and sensitive and important ecosystems in the area are showing varying degrees of impact. Management measures are needed to ensure ongoing sustainable development of the area. In this study, different interpolation techniques were evaluated to calculate values for unsampled variables rainfall and groundwater elevation. Local deterministic techniques as well as geostatistical techniques were used. It was found that geostatistical techniques, especially with collateral information, such as topography, provided a more accurate result. For environmental studies of this nature, Kriging is recommended as interpolation technique. The underlying data will determine the selection of the particular type of Kriging. Data was extracted from a customized relational database, geoMon, used for data capture, retrieval, processing and reporting. Ease of data extraction facilitated analysis. The interpolated grids were applied in two scenarios: Recharge calculations and quantification as well as a new classification approach according to Resource Directed Measures (RDM). Management classes were defined based on GIS-derived data. / AFRIKAANSE OPSOMMING: Die Sandveld, ‘n aartappelverbouingsgebied in die Wes-Kaap, ondergaan aansienlike grondwateronttrekking vir beide munisipale sowel as landbou doeleindes. Die klimaat is dor en droog en sensitiewe en belangrike ekosisteme in die area ondervind wisselende impakvlakke. Bestuursmaatreëls word benodig om volhoubare ontwikkeling van die area te verseker. In hierdie studie is verskillende interpolasie tegnieke om onbekende waardes vir veranderlikes gebruik in grondwater evaluasie te bereken, evalueer. Lokale deterministiese tegnieke sowel as geostatistiese tegnieke is gebruik. Geostatistiese tegnieke, veral gebruik saam met addisionele inligting soos topografie, bereken meer akkurate resultate. Vir omgewingsstudies van hierdie aard, word Kriging aanbeveel as interpolasie tegniek. Eienskappe van die onderliggende data word gebruik om die tipe Kriging aan te dui. Data is onttrek uit ‘n gebruikersaangepaste databasis, geoMon, wat gebruik is vir datavaslegging, onttrekking, prosessering en verslaggewing. Die gemak waarmee data onttrek kon word het analise vergemaklik. Geïnterpoleerde data is gebruik vir grondwateraanvullingsberekeninge en -kwantifisering sowel as ‘n nuwe benadering tot klassifikasie volgens hulpbron gerigte maatreëls. Bestuursklasse gebaseer op GIS-afgeleide data, is gedefinieer.