Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The effect of long-term tillage on basic soil properties with respect to sustainability was investigated in this dissertation. Over the last three decades soil conservation has become an important prerequisite for sustainable agriculture. The primary aim of this study was to evaluate the effect of different tillage practices on the physical and some of the chemical properties of soil after 37 years of continuous application. This study was conducted on the Langgewens experimental farm, 18 km north of Malmesbury in the Western Cape. The experiment was initiated in 1975 on a Glenrosa (Haploxeralf) soil form with a gravelly sandy-loam texture. It was treated with four main tillage methods, namely conventional, tine, minimum and no-tillage. Important basic soil properties studied were the electrical conductivity (EC) and total carbon percentage, water stable aggregate percentage, bulk density and hydraulic conductivity. Most of the properties were analysed for the 0-100 mm and 100-200 mm depths. Seasonal bulk density variation for the 0-100 mm soil depth was determined by a Troxler surface gamma-neutron meter for in situ measurement. ANOVA’s and Tukey’s LSD posthoc tests were computed to assess whether significant statistical differences existed between tillage treatments. No-tillage proved to be beneficial in terms of salinity and had the lowest electrical conductivity, indicating that salts leeched out of the profile. Total carbon content was in general very low and in the 0-100 mm soil depth it decreased in the order of: no (0.92%), minimum (0.86%), tine (0.83%) and conventional tillage (0.51%). Aggregate stability was significantly the lowest under conventional (47.82%) and tine tillage (45.02%) compared to minimum (61.43%) and no-tillage (78.40%) at 0-100 mm depth. This can be explained by the relatively low amount of total carbon in the soil combined with the tillage intensity. The same trend was observed for the 100-200 mm depth. Significant correlation between total carbon content and aggregate stability for the 0-100 mm confirmed that an increase in total carbon in the soil would lead to an increase in aggregate stability. Significant, increased aggregate stability under the no-tillage treatment would therefore indicate that there may be some stable structure present in the soil. Seasonal bulk density variation was the lowest in no-tillage, which supports the manifestations of stable soil structure. More intensive tillage treatments such as conventional and tine tillage initially showed lower bulk densities, but only for the first month. Thereafter it increased to significantly higher values as the season progressed. This was mainly as a result of hardsetting of the soil which is driven by natural processes and rainfall. It is also due to the sandy loam texture that is particularly prone to compaction. Hydraulic conductivity studied for conventional and no-tillage showed significant differences. No-tillage (41 mm.h-1) showed a noticeably higher conductivity, which remained constant compared to conventional tillage (20 mm.h-1) that decreased over time. The main reasons for this increased hydraulic conductivity under no-tillage was higher water stable aggregates and lower bulk density. In the long term no-tillage thus stimulated structure formation of a Glenrosa soil form that significantly improved soil properties studied. These properties may influence processes such as water infiltration, water storage, run-off and drainage positively, due to soil property interaction. No-tillage, in terms of sustainability, quantified by the soil properties studied, thus proved to be superior compared to conventional and tine tillage but to a lesser extent if compared to minimum tillage. / AFRIKAANSE OPSOMMING: In hierdie tesis word die effek van langtermynbewerking op basiese grondeienskappe met betrekking tot volhoubaarheid ondersoek. Oor die afgelope drie dekades het grondbewaring ‘n belangrike aspek in landbou geword, ten einde volhoubaarheid te verseker. Die primêre doel van hierdie studie was om die effek van verskillende bewerkingspraktyke op die fisiese en chemiese eienskappe van grond na 37 jaar van deurlopende bewerking te ondersoek. Die studie is uitgevoer op die Langgewens eksperimentele plaas, 18 km noord van Malmesbury in die Wes-Kaap. Die eksperiment is in 1975 geïnisieer op 'n Glenrosa (Haploxeralf) grondvorm met ʼn klipperige sandleem-tekstuur. Dit bestaan uit vier hoof-bewerkingsbehandelings, naamlik konvensionele, tand-, minimum en geenbewerking. Belangrike basiese grondeienskappe wat bestudeer is, is die elektriese geleidingsvermoë (EG) en die totale persentasie koolstof, persentasie waterstabiele aggregate, bulkdigtheid en hidrouliese geleiding. Die meeste van die eienskappe is ontleed op die 0-100 mm en 100-200 mm diepte. Seisoenale bulkdigtheidsvariasie vir die 0-100 mm gronddiepte is bepaal deur 'n Troxler oppervlak gamma-neutron meter deur middel van in situ meting. ANOVA en Tukey se LSD posthoc-toetse is bereken om te bepaal of daar statisties-beduidende verskille tussen die bewerkingsmetodes is. Geenbewerking het geblyk voordelig te wees in terme van die soutgehalte en het die laagste elektriese geleidingsvermoë gehad, wat daarop dui dat die soute uit die profiel loog. Die totale koolstofinhoud was oor die algemeen baie laag en in die 0-100 mm gronddiepte het dit afgeneem in die volgorde geen- (0.92%), minimum- (0.86%), tand- (0.83%) en konvensionele bewerking (0.51%). Aggregaatstabiliteit was betekenisvol die laagste onder konvensionele (47.82%) en tandbewerking (45.02%) in vergelyking met die minimum (61.43%) en geenbewerking (78.40%) by die 0-100 mm diepte en kan verduidelik word deur die relatief lae totale koolstofinhoud in die grond gekombineer met die bewerkings-intensiteit. Dieselfde tendens is waargeneem vir die 100-200 mm diepte. ‘n Beduidende korrelasie tussen totale koolstofinhoud en aggregaatstabiliteit is vir die 0-100 mm diepte gevind en dit bevestig dat 'n toename in totale koolstof in die grond sal lei tot 'n toename in aggregaatstabiliteit. Betekenisvolle verhoogde aggregaatstabiliteit onder die geenbewerking-behandeling sal dus aandui dat die grond 'n meer stabiele struktuur vertoon. Seisoenale bulkdigtsheidsvariasie was die laagste in geenbewerking en ondersteun die manifestasies van 'n stabiele grondstruktuur. Meer intensiewe bewerkingsbehandelings, konvensionele en tandbewerking het vir die eerste maand ‘n laer bulkdigtheid getoon, waarna dit tot aansienlik hoër waardes gestyg het soos die seisoen verloop het. Dit was hoofsaaklik as gevolg van grondkonsolidering wat gedryf word deur natuurlike prosesse soos reënval en ook as gevolg van die sandleemtekstuur wat veral geneig is tot verdigting. Hidrouliese geleiding is bestudeer vir konvensionele en geenbewerking en het beduidende verskille getoon. Geenbewerking (41 mm.h-1) het 'n merkbare hoër geleidingsvermoë gehad wat konstant gebly het, in vergelyking met konvensionele bewerking (20 mm.h-1) wat met die verloop van tyd afgeneem het. Die vernaamste redes vir hierdie verhoogde hidrouliese geleiding onder geenbewerking is hoër waterstabiele aggregate en ‘n laer bulkdigtheid. Op die langtermyn het geenbewerking dus struktuurvorming van 'n Glenrosa-grondvorm gestimuleer, wat die grondeienskappe wat bestudeer is, aansienlik verbeter het. Hierdie eienskappe kan prosesse soos waterinfiltrasie, waterretensie, -afloop en -dreinering positief beïnvloed as gevolg van grondeienskapinteraksie. Geenbewerking, in terme van volhoubaarheid, gekwantifiseer deur die grondeienskappe wat bestudeer is, is dus bewys as superieur in vergelyking met konvensionele en tandbewerking, maar tot 'n mindere mate in vergelyking met minimumbewerking. / Water Research Commission

Thesis (MScAgric)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The herbicide atrazine (ATZ, 2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) has been identified as an environmental endocrine disruptor and possible human carcinogen. The presence of atrazine, along with its degradation products, in soils and water supplies therefore raises concern. Atrazine biodegradation in soils is well-covered to date, however, atrazine degradation by abiotic mineral surfaces, and the chemical mechanism by which it occurs, is not fully understood. Furthermore, with a changing global climate, the effects of wetting and drying cycles on soil processes (e.g. atrazine degradation) is largely unknown, but increasing in importance. This study therefore investigated atrazine degradation on six common soil mineral surfaces, namely birnessite, goethite, ferrihydrite, gibbsite, Al3+-saturated smectite and quartz, as well as the effects that drying these surfaces has on atrazine degradation. In the first part, a comparison was conducted between the reactivity of fully hydrated and drying mineral surfaces toward atrazine, by reacting atrazine-mineral mixtures under both moist and ambient drying conditions, in parallel, for 14 days. Under moist conditions, none of the mineral surfaces degraded atrazine, but under drying, birnessite and goethite degraded atrazine to non-phytotoxic hydroxyatrazine (ATZ-OH, 2-hydroxy-4-ethylamino-6-isopropylamino-1,3,5-triazine) as major product and phytotoxic deethylatrazine (DEA, 2-chloro-4-amino-6-isopropylamino-1,3,5-triazine) as minor product. The mineral surface reactivity was birnessite (66% degradation) > goethite (18% degradation) >> other mineral surfaces (negligible degradation), indicating possible atrazine oxidation. In the second part, the effects of drying rate were investigated on birnessite only (the most reactive surface), by conducting the drying (1) gradually at ambient rates, (2) rapidly under an air stream, and (3) gradually in the absence of water using only organic solvent. After 30 days of ambient drying, 90% of the atrazine was degraded to ATZ-OH and DEA, but the same extent of degradation was achieved after only 4 days of rapid drying with an air stream. Thirty days of gradual drying using only organic solvent did not increase atrazine degradation compared to the water-moist drying surface. In each case, degradation initiated at a critical moisture content of 10% of the original moisture content. In the third part, the degradation mechanism was further investigated. To test for the possible oxidation of atrazine by the birnessite surface, moist atrazine-birnessite mixtures were dried under a nitrogen (N2) stream to eliminate possible oxidation by atmospheric oxygen (O2). Dissolved Mn2+ was extracted at the end of the experiment to observe any reduction of birnessite. Under N2, the same products were formed as before, with no appreciable Mn2+ production, indicating non-oxidative atrazine degradation by birnessite. The final part investigated the effects ultraviolet (UV) radiation has on the degradation of atrazine by drying mineral surfaces. The UV-radiation enhanced the degradation of atrazine, but no other degradation products were formed. It was therefore concluded that atrazine degradation on redox-active soil mineral surfaces is enhanced by drying, via a net non-oxidative mechanism. Furthermore, this drying-induced degradation is an atrazine detoxification mechanism which could be easily applied through agricultural practices such as windrowing, ploughing and any other practice that (rapidly) dries a Mn- or Fe-oxide rich agricultural soil. / AFRIKAANSE OPSOMMING: Die onkruiddoder atrasien (ATS, 2-chloro-4-etielamino-6-isopropielamino-1,3,5-triasien) is as 'n omgewings endokriene versteurder en moontlike menslike karsinogeen geidentifiseer. Die teenwoordigheid van atrasien, tesame met sy afbreekprodukte, in grond en water toevoere wek dus kommer. Die bio-afbreking van atrasien in gronde is tot dusver goed gedek, maar die afbreking van atrasien deur abiotiese mineraaloppervlaktes, en die chemiese meganisme waarmee dit plaasvind, word nie heeltemal verstaan nie. Verder, met 'n veranderende globale klimaat, is die effekte van benatting- en drooging-siklusse op grondprosesse (bv. atrasien afbreking) grootliks onbekend, maar toenemend belangrik. Daarom het hierdie studie atrasien afbreek op ses algemene mineraaloppervlaktes, naamlik birnessiet, goethiet, ferrihidriet, gibbsiet, Al3+-versadigde smektiet en kwarts, ondersoek, asook die effekte wat drooging van hierdie oppervlaktes op atrasien afbreking het. In die eerste deel, was 'n vergelyking gedoen tussen die reaktiwiteit van volgehidreerde en droëende mineraaloppervlaktes teenoor atrasien, deur atrasien-mineraal mengsels, in parallel, onder albei nat en omliggende droogings toestande te reageer vir 14 dae. Onder nat toestande, het geeneen van die mineraaloppervlaktes atrasien afgebreek nie, maar onder drooging het birnessiet en goethiet atrasien afgebreek na nie-fitotoksiese hidroksieatrasien (ATS-OH, 2-hidroksie-4-etielamino-6-isopropielamino-1,3,5-triasien) as hoofproduk en fitotoksiese deetielatrasien (DEA, 2-chloro-4-amino-6-isopropielamino-1,3,5-triasien) as minder-produk. Die mineraaloppervlakte-reaktiwiteit was birnessiet (66% afbreking) > goethiet (18% afbreking) >> ander mineraaloppervlaktes (geringe afbreking), wat moontlike atrasien oksidasie aandui. In die tweede deel, is die effekte van droogingstempo ondersoek, op birnessiet alleenlik (die mees reaktiewe oppervlak) deur drooging by (1) 'n omliggende geleidelike tempo, (2) 'n versnelde tempo onder 'n lugstroom, en (3) 'n geleidelike tempo in die afwesigheid van water, deur slegs gebruik te maak van 'n organiese oplosmiddel. Na 30 dae se geleidelike drooging, is 90% van die atrasien afgebreek na ATS-OH en DEA, maar dieselfe hoeveelheid afbreking is bereik na slegs 4 dae onder versnelde drooging met die lugstroom. Dertig dae van geleidelike drooging met slegs organiese oplosmiddel het nie atrasien afbreking vermeerder in vergelyking met die water-nat droëende oppervlak nie. In elke geval, is afbreking geïnisieer by 'n kritiese water inhoud van 10% van die oorspronklike water inhoud. In die derde deel is die afbrekingsmeganisme verder ondersoek. Om te toets vir die moontlike oksidasie van atrasien deur die birnessiet oppervlak, is nat atrasien-birnessiet mengsels onder stikstof (N2) gedroog, om die moontlike oksidasie deur atmosferiese suurstof (O2) te verhoed. Opgeloste Mn2+ was teen die einde van die eksperiment geekstraëer om enige reduksie van birnessiet waar te neem. Onder N2 is dieselfde produkte as voorheen gevorm, met geen aansienlike Mn2+ produksie nie, aanduidend van 'n nie-oksideerende afbreek van atrasien deur birnessiet. Die laaste deel het die effekte van ultraviolet (UV) straling op die afbreek van atrasien op droëende mineraaloppervlaktes ondersoek. Die UV-straling het atrasien afbreek vermeerder, maar geen ander afbreek-produkte is gevorm nie. Die gevolgtrekking is dus dat atrasien afbreking op redoks-aktiewe mineraal-oppervlaktes verhoog word met drooging, deur 'n netto nie-oksidasie meganisme. Verder is hierdie drooging-geinduseerde afbreking 'n atrasien ontgiftingsmeganisme wat eenvoudig toegepas kan word deur landboupraktyke soos windrying, ploeg en ander praktyke wat (vinnig) 'n Mn- of Fe-oksied ryke landbou grond verdroog. / National Research Foundation (NRF)

Thesis (MA) -- Stellenbosch University, 1932. / VOORWOORD: Die doel van hierdie verhandleing is in die eerste plek om daarop te wys dat in Suid-Afrika meer wyn geproduseer word as wat tans van die hand gesit kan word teen 'n prys wat die produsente genoegsaam sal vergoed. Uit die oorproduksie en die heersende lae pryse volg dit dat die posiesie van die wynboere erg kritiek en haglik is. Die industrie gaan nou juis weer deur diepe waters en iets moet gedoen word om die bedryf van ondergang te red en vir die toekoms op 'n vaste basis te plaas.

Thesis (PhD(Agric))--Stellenbosch University, 2012. / ENGLISH ABSTRACT: There is an increasing demand for canola (Brassica napus L.), an emerging oilseed crop in South Africa. Canola thrives in the Western Cape. However, yet low yields are still obtained within the production areas with poor and or variable responses to nitrogen applications. Crop nutrition and specifically the contribution of sulphur (S) to nitrogen (N) use and selection of nutrient efficient genotypes can be strategies of considerable significance in increasing yields. This study investigated growth, yield and quality responses of canola to different N (0, 30, 60, 90 and 120 kg N ha-1) and S (0, 15 and 30 kg S ha-1) fertilisation rates in field trials at different localities, during the 2009-2011 period. Responses to N and S under optimum growing conditions and responses of different cultivars were investigated in unison in glasshouse trials at the Department of Agronomy of the University of Stellenbosch. Locality and growing season (year) significantly affected nutrient content in plants at flowering (90 days after planting), dry mass production as well as yield and quality of canola in field trials at five different localities during the 2009-2011 period. Growth and yield were also affected by N application rate in both field and glasshouse trials. Sulphur applications did not have an effect on vegetative growth, but rather stimulated flower and pod production in glasshouse trials and resulted in higher grain yields in field trials. Response depends largely on rainfall and S content of the soil. Highest yields were, on average, obtained with application rates of 120 kg N and 30 kg S ha-1, while glasshouse trials showed that even higher rates may be considered under optimum growing conditions. High application rates of N and S also improved water use efficiency from approximately 4-5 kg grain yield to about 8-9 kg grain yield mm-1 of rain during the growing season. Agronomic efficiencies of applied N decreases with increasing N rates and values of about 8 kg grain yield increase per kg of N applied at N rates of 120 kg N ha-1 indicated that high N rates may improve profit margins of canola as long as the cost of N is not more than eight times the producers price of canola. Agronomic efficiencies of N applications are improved if 15 kg S ha-1 is applied complimented with high rainfall, but not with applications of 30 kg S ha-1. Improved agronomic efficiencies of S applications shown at higher N rates, confirmed the dependency of S responses to sufficient availability of nitrogen. Sulphur applications, in contrast to N, resulted in an increase in oil content of the grain in field trials. Yield responses of different cultivars to nitrogen fertilisation under glasshouse conditions differed, with better responses obtained within short and medium season cultivars, than with a late maturing (long season cultivar), in spite of a better vegetative (dry mass) response of the later maturing cultivar. These results may indicate differences in the growth habit of different cultivars, but more research in this regard is needed. / AFRIKAANSE OPSOMMING: Canola (Brassica napus L.), ‘n relatief nuwe oilsaadgewas wat goed aangepas is, word in ‘n toenemende mate in die produksiegebiede van die Weskaap verbou. Lae opbrengste en wisselvallige reaksies teenoor stikstofbemesting word egter verkry ten spyte van die gewas se hoë stikstofbehoefte en dit mag moontlik aan swaweltekorte toegeskryf word. In hierdie ondersoek is die groei-, opbrengs- en kwaliteitsreaksie van canola teenoor verskillende N (0, 30, 60, 90 en 120 kg N ha-1) en S (0, 15 en 30 kg S ha-1) bemestingspeile in droëland proewe op verskillende lokaliteite bestudeer gedurende die 2009-2011 groeiseisoene. Reaksies teenoor N en S onder optimale groeitoestande en vir verskillende cultivars is in glashuisproewe van die Departement Agronomie van die Universiteit van Stellenbosch, uitgevoer. Die chemiese samestelling van die plante tydens blomstadium (90 dae na plant), asook droëmateriaal produksie, graanopbrengs en kwaliteit het betekenisvol verskil tussen die lokaliteite, maar lokaliteitsverskille is ook deur die seisoene beïnvloed. Die ontwikkeling, groei en graanopbrengs van die canola is ook beïnvloed deur die stikstofbemestingspeile in beide die veld en glashuisproewe. Swawelbemesting het nie die vegetatiewe groei van canola beïnvloed nie, maar het blom en peulproduksie in glashuisproewe en graanopbrengste in veldproewe verhoog. Die reaksie van canola teenoor die swawelbemesting is grootliks bepaal deur die swawelinhoud van die grond asook klimaatsfaktore soos reënval. In die algemeen is die hoogste canola opbrengste in veldproewe met toedienings van 120 kg N en 30 kg S ha-1 verkry, maar glashuisproewe het getoon dat hoër toedieningspeile nodig mag wees onder optimale groeitoestande soos in besproeiingsgebiede. Hoë toedieningspeile van N en S het veroorsaak dat die waterverbruiksdoeltreffendheid toegeneem het van 4-5 kg graanopbrengs per mm reën tot sowat 8-9 kg graan opbrengs per mm reën. Agronomiese doeltreffendheid van toegediende stikstofbemesting het afgeneem met toenemende N peile, maar waardes van ongeveer 8 kg opbrengsverhoging per kilogram N toegedien met stikstofpeile van 120 kg ha-1, toon dat hoë N toedieningspeile mag steeds winsgrense verhoog mits die prys van een kilogram N nie meer is as agt maal die produsente prys van canola is nie. Agronomiese doeltreffendheid van stikstofbemesting is verhoog deur ook 15 kg S per hektaar toe te dien, maar nie deur die toediening van 30 kg S ha-1 nie. Die agronomiese doeltreffendheid van S toedienings het slegs by die gelyktydige toediening van hoë stikstoftoedienings toegeneem, wat die wisselwerking tussen N en S ten opsigte van graanopbrengs bevestig. In teenstelling met stikstof het swawel toedienings die olie-inhoud van canola in die veldproewe verhoog. In glashuisproewe is gevind dat kort en medium groeiseisoen cultivars, ten spyte van ‘n groter vegetatiewe reaksie van die lang groeiseisoen cultivars, groter opbrengsreaksies teenoor stikstof- en swawelbemesting toon. Meer navorsing word egter in hierdie verband benodig.

Thesis (MScAgric)--Stellenbosch University, 1955. / INTRODUCTION: The earliest work on African Aphids was done by Pred. V. Theobald. His first monograph appeared in 1914, and dealt with only thirty-five species of which nine where described so now to science. His later paper were published in the Bulletinof Entomological Research (1914, 1915, 1918 and 1920), and in these papers a total of fifty-five new species, were described.

Thesis (PhD (Agric.) -- Stellenbosch University, 1984. / INTRODUCTION: The study of seed dormancy and germination has for centuries occupied the minds of agronomists, physiologists, brewers, bakers and, more recently, weed scientists. The agronomist requires that the seed that he sows will germinate rapidly and uniformly and produce a vigorous healthy seedling .. The physiologist is interested in the understanding of the basic processes involved at the molecular level, and the geneticist in the inheritance of the quiescent character of the seed. Brewers seek a seed that will retain its viability at least until the following crop is harvested but which will also, on imbibition, rapidly set in motion those processes that will convert starch into sugar. The baker is concerned with the baking quality of the seed and, as far as he is concerned~ the more dormant the seed the better, as this eliminates the problem of pre-harvest sprouting which is very detrimental to baking quality. The weed scientist seeks to encourage all weed seeds present in the soil to germinate simultaneously so as to enable him to destroy the weed population with one application of herbicide or a single cultivation.

Thesis (PhDAgric)--Stellenbosch University, 2006. / ENGLISH ABSTRACT: The South African pork industry is characterised by low slaughter weights when compared to the rest of the world. This inevitably leads to a smaller number of kilograms produced per unit fixed cost and subsequently the efficiency of production is reduced. A study was conducted with 189 pigs representing three sex types (boar, gilt and castrate) and five commercial genotypes. Pigs entered into the trial at an age of 10 weeks and an average live weight of 27.5±2.5kg. Treatments were according to slaughter weight ranging between 62 and 146kg. Production and carcass characteristics, meat quality and processing characteristics and sensory attributes were assessed. Production characteristics assessed included live weight gains, intake, P2 backfat thickness and feed conversion ratio. Main observed effects were associated with slaughter weight and its interaction with sex type. Rates of change in parameters measured were described. Growth and feed conversion ratio were described using linear models while cumulative feed intake was described using 2nd order polynomials. Carcass characteristics assessed included carcass weight, dressing percentage, carcass length, ham length, ham circumference, chest depth, backfat thickness measurements, muscle depth, eye muscle area, subcutaneous fat area, intramuscular fat area as well as ratios of eye muscle to subcutaneous and intramuscular fat area. The main statistical differences observed were for slaughter weight. Significant sex type differences were observed for dressing percentage and some fat and muscle depth measurements. Meat quality characteristics assessed included colour measurements, tenderness, drip loss and water holding capacity. Main differences observed were for slaughter weight. Carcass yields were assessed in terms of absolute and percentage yields of commercial cuts as well as yield of processable lean meat. In terms of the absolute and percentage yields of the commercial cuts, the main statistical differences observed were for slaughter weight. Changes in cut yield with increased slaughter weight are described using regression analysis. In terms of yields obtained for processable lean meat, the main statistical differences observed were for slaughter weight. Sex type differences were only observed for percentage belly and topside processable lean meat and percentage brine uptake of belly bacon, whole gammon ham and topside gammon. Genotypic differences were observed for percentage yield of processable lean meat of the neck and whole gammon and percentage fresh to smoke losses of back bacon and whole gammon ham. Sensory attributes were assessed using gammon ham, belly bacon and fresh loin. Observed slaughter weight differences were inconsistent and did not appear to change with an increase in slaughter weight. Once meat was processed, most sensory differences were no longer observed. Increased slaughter weight generally led to increased juiciness and decreased tenderness. It is therefore concluded that the current South African pig genotypes have the ability to maintain high growth rates for a much longer time and therefore can be slaughtered at a higher weight without detrimental effect on production efficiency, carcass and meat quality characteristics, yields of commercial and processable lean meat, processing characteristics and ultimately sensory characteristics of the meat produced. / AFRIKAANSE OPSOMMING: Die Suid-Afrikaanse varkbedryf word gekenmerk deur relatiewe lae slagmassas in vergelyking met die res van die wêreld. Dit lei onvermydelik tot ‘n kleiner aantal kilogramme vleis geproduseer per eenheid vaste koste. ’n Studie is gevolglik gedoen met die doel om die tempo’s van verandering van sekere produksie-, karkas-, vleis- en proseseringseienskappe te kwantifiseer ten einde die optimale slagmassa te bepaal wat vir alle rolspelers in die bedryf tot voordeel sal wees. Die studie is gedoen met 189 diere wat vyf kommersiële genotipes en drie geslagstipes (beer, sog en kastraat) verteenwoordig het. Varke is op ’n ouderdom van 10 weke met ’n gemiddelde lewende massa van 27.5±2.5kg in die proef opgeneem. Behandelings was volgens slagmassa en het gevariëer van 62 tot 146kg. Produksieparameters en karkas-, vleiskwaliteits-, en proseseringseienskappe sowel as sensoriese eienskappe, is ëvalueer. Produksieeienskappe wat ëvalueer is sluit in: groei, inname, P2 rugvetdikte en voeromset-verhoudings. Hoofeffekte wat waargeneem is, was vir slagmassa en interaksies van slagmassa met geslag. Tempo van verandering in die parameters gemeet, is beskryf. Groei en voeromsette is beskryf deur die passing van ‘n linieêre model terwyl kumulatiewe voerinname beskryf is deur ‘n 2de orde polinoom. Karkaseienskappe wat ëvalueer is, sluit in: karkasmassa, uitslagpersentasie, karkaslengte, hamlengte, hamomtrek, borsdiepte, rugvetdikte, spierdiepte, oogspieroppervlak, onderhuidse vet-, binnespierse vetoppervlak en verhoudings van oogspier- tot-vetoppervlakke. Die hoof statistiese effekte wat waargeneem is, was vir slagmassa. Betekenisvolle geslagsverskille is waargeneem vir uitslagpersentasie en sommige, vet- en spierdieptemetings. Genotipiese verskille is waargeneem vir sommige vetmetings. Vleiskwaliteiteienskappe wat beoordeel is, het kleur, drupverlies, waterbindingsvermoë en sagtheid ingesluit. Hoofeffekte waargeneem was vir slagmassa. Karkasopbrengste is ëvalueer in terme van absolute en persentasie opbrengste van kommersiële snitte sowel as prosesseerbare maer vleis. In terme van absolute en persentasie opbrengste van kommersiële snitte, was meeste van die variasie beskryf deur slagmassa. Tempo van verandering in die persentasie opbrengste van die snitte word beskryf. In terme van opbrengste vir proseseerbare maer vleis is die hoof statistiese verskille waargeneem vir slagmassa. Geslagverskille is waargeneem vir persentasie streepspek en binneboud maer vleis opbrengs vir prosesering en persentasie pekelopname van streepspek, heel varkboud ham en binneboud ham. Genotipe verskille is waargeneem vir persentasie opbrengs van maer vleis vir prosesering van die nek en heelboud en persentasie vars-tot-klaar-gerook verliese van rugspek en heelboud hamme. Sensoriese eienskappe is ëvalueer vir twee geprosesseerde en een vars snit. Slagmassa-effekte was nie konstant nie en parameters het klaarblyklik nie verander soos slagmassa verander het nie. Sodra vleis geprosesseer is, het die meeste sensoriese verskille verdwyn. Beide sappigheid en taaiheid het toegeneem met ‘n toename in slagmassa. Dit kan dus aanvaar word dat, gegewe die huidige Suid Afrikaanse genotipes, dit moontlik is om swaarder karkasse te produseer sonder noemenswaardige nadelige effekte op karkas-, vleis-, opbrengste-, prosesering- en sensoriese eienskappe van varkvleis.

Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The influence of chemical seed treatments on the germination, seedling survival and yield of canola (cv. Varola 44) was investigated in a series of incubation studies, glasshouse experiments, as well as field trials in the canola producing areas in the Western Cape Province. Incubation experiments were conducted to compare germination and seedling growth of untreated (control) seed with that of seed treated at different application rates (0.5, 1.0 and 2.0 times the recommended) of Cruiser® and SA-combination (which consists of Thiulin® at 0.5g a.i.; Apron® at 0.0815 g a.i.; Gaucho® at 0.6125 g a.i. and Rovral® at 0.9975 g a.i.). The results indicated that seed treatment (all rates of SA-combination and highest rate of Cruiser) delayed germination and seedling growth, especially if the seed was subjected to the Accelerated Ageing Test. Glasshouse studies with pasteurised soil at different water contents, seed sources (storage periods) and planting depths confirmed the phytotoxic effects of the chemical seed treatments in the absence of soil borne pathogens. From the results it became clear that extreme water conditions (very wet or dry) increased the suppressing effect on germination and seedling growth, but that no phytotoxic reactions occurred in moist (favourable soil water conditions) soil, regardless of application rate of the chemicals used, planting depth and seed source. In a second glasshouse experiment conducted in moist soil (kept at 50% of field water capacity to prevent any toxic effects) from seven different localities that were naturally infested with pathogens, both chemicals proved to be effective where soil borne pathogens (Rhizocfonia so/ani and Pythium spp.) occurred. No clear trend could however be found due to either chemical or application rates used. Finally, field trials were conducted to study the effect of chemical seed treatments on the plant populations and yield of canola planted in different row widths (17 and 34 cm) and seeding rates (3, 5 and 7 kq.ha'). Results showed that treated seeds produced more plants.rn" and yielded more than untreated seeds at Roodebloem Experimental Farm, while the highest seeding rate produced significantly more plants.rn" (Roodebloem and Langgewens Experimental Farms), but not significantly higher yields than the lowest seeding rate at the same locality. Although row width did not have an effect on plant population, yield (Roodebloem 2003) was significantly less at the wider (34 cm) rows. As in earlier experiments, no consistent differences between the two chemicals used were found. These results clearly illustrated both the negative (in the absence of pathogens) and positive (where soil borne pathogens do occur) effects that chemical seed treatments may have on the germination, seedling growth and even yield of canola under local environmental and soil conditions. Because no significant differences were found between the chemicals used, both chemicals should be regarded as efficient. More research, especially under field conditions and with more cultivars, is needed before the registration of a chemical for seed treatment could be considered. / AFRIKAANSE OPSOMMING: Die invloed van chemiese saadbehandeling op die ontkieming, saailing oorlewing en opbrengs van canola (cv. Varola 44) is ondersoek in 'n reeks inkubasie studies, glashuis eksperimente en veldproewe in die canolaproduserende gebiede in die Wes Kaap Provinsie. Inkubasie eksperimente is uitgevoer om die ontkieming en saailing groei van onbehandelde (kontrole) saad te vergelyk met dié van saad wat behandel is teen verskillende dosisse (0.5, 1.0 en 2.0 keer die aanbevole) van Cruiser® en SA-kombinasie (wat bestaan uit Thiulin® teen 0.5g a.i.; Apron® teen 0.0815 g a.i.; Gaucho® teen 0.6125 g a.i. en Rovral® teen 0.9975 g a.i.). Die resultate het aangedui dat saadbehandeling (vir alle dosisse van SAkombinasie en die hoogste dosis van Cruiser) ontkieming en saailing groei vertraag, veral wanneer die saad onderwerp was aan die Versnelde Verouderings Toets. Glashuis studies met gepasteuriseerde grond by verskillende waterinhoude, saad bronne (stoor periodes) en plantdieptes, het die fitotoksiese effekte van die chemiese saadbehandelings bevestig in die afwesigheid van grondgedraagde patogene. Vanuit die resultate het dit duidelik geword dat ekstreme water toestande (baie nat of droog) die onderdrukkende effek op ontkieming en saailinggroei verhoog het, maar dat geen fitotoksiese reaksies plaasgevind het in klam (gunstige grondwater toestande) grond nie, ongeag die dosisse of chemikalieë gebruik, plantdiepte en saad bron. In 'n tweede glashuis eksperiment uitgevoer in klam grond (gehou by 50% van veldwaterkapasiteit om toksiese effekte te voorkom) van sewe lokaliteite wat natuurlik besmet was met patogene, was beide chemikalië effektief waar grondgedraagde patogene (Rhizoctonia so/ani en Pythium spp.) voorgekom het. Geen duidelike tendens is egter waargeneem vir enige van die chemikalieë of dosisse nie. Laastens is veldproewe uitgevoer om die effek van chemiese saadbehandelings op plant populasies en opbrengs te bepaal van canola geplant in verskillende rywydtes (17 en 34 cm) en saaidigthede (3, 5 en 7 kg.ha-1). Resultate het aangedui dat behandelde saad meer plante.rn" produseer en 'n groter opbrengs lewer as onbehandelde saad by Roodebloem Eksperimentele Plaas, terwyl die hoogste saaidigtheid betekenisvol meer plante.m" (Roodebloem en Langgewens Eksperimentele Plase), maar nie betekenisvol hoër opbrengste gelewer het as die laagste saaidigtheid by dieselfde lokaliteit nie. AI het rywydte nie 'n effek op plant populasie gehad nie, was opbrengs (Roodebloem 2003) betekenisvol minder by die wyer (34 cm) rye. Soos in vroeëre eksperimente is geen konsekwente verskille tussen die twee chemikalieë gevind nie. Hierdie resultate illustreer duidelik beide negatiewe (in die afwesigheid van grondgedraagde patogene) en positiewe (in die aanwesigheid van grondgedraagde patogene) effekte wat chemiese saadbehandelings op ontkieming, saailing groei en selfs opbrengs van canola onder plaaslike omgewings en grondtoestande kan hê. Omdat geen betekenisvolle verskille tussen die chemikalieë gevind is nie, moet beide chemikalieë as doeltreffend aanvaar word. Meer navorsing, veralonder veldtoestande en met meer kultivars, is egter nodig voordat die registrasie van 'n chemiese middel vir saadbehandeling oorweeg kan word.

Thesis (PhD) -- Stellenbosch University, 2003. / Please refer to full text to view abstract. / ENGLISH ABSTRACT: The effects of different land use practices on soil quality in South Africa were investigated in five contrasting biomes, with a particular emphasis on the tendency of soils to crust and soil C content. Soil quality is a nebulous concept and its applicability in the South African landscape is scrutinised. A wide range of chemical and physical soil properties were examined. The tendency of soils to crust was assessed using modulus of rupture, water dispersible clay and a new method of laboratory infiltration which was verified with rainfall simulation. Crusting was greater in bare, exposed soils than soils under vegetation and varied with soil parent material. Differences in crusting are explained by factors relating to clay dispersion such as clay mineralogy, soil C, labile or readily oxidisable C, concentration of soluble salts, soil texture and exchangeable Na percentage (ESP). Results from longterm bum plots in savanna and grassland revealed that annual burning can increase the tendency of soils to crust. Greater crusting in burnt plots is ascribed to greater dispersion of clay, which in tum is attributed to a decline in soil C, a decline in EC and an increase in ESP. The loss of nutrients from burnt plots over time is ascribed to removal of ash in surface runoff. Calcium, Mg, and K were lost more readily than Na probably because plants take up these nutrients in greater concentration than Na. The net effect was an increase in ESP. Crusting on burnt plots may be self-perpetuating, because increased runoff is likely to incsease the loss of soluble salts. Removal of vegetation due to cultivation, grazing or burning reduced soil C at all sites. Mean soil C in the 0-1 cm layer of unburnt plots in the Kruger National Park was more than three times greater than in burnt plots (2.7 vs 0.8%). The difference in soil C between treatments decreased with depth and illustrated that sampling to depths greater than a few centimetres can obscure effects of land use. The top few centimetres of soil have a disproportionate effect on soil infiltrability and nutrient cycling. This layer was named the pedoderm. Tree cover on burnt plots in the southern Kruger Nationa--l- Park is highly variable, and was hypothesised to be a function of herbivory pressure. Herbivores tended to congregate on plots with the greatest clay, Zn and Mn content and the lowest tree cover. It is suggested that soil properties determine the abundance of herbivores after fire, which in tum affects tree cover. In the Eastern Cape,intensive stocking with goats transforms dense thicket to an open savanna. Soils from goat-transformed sites had a greater tendency to crust than soils from intact thicket, probably due to aggregate weakening associated with a decline in soil C. Mean soil C content of intact thicket was almost double that of goat-transformed thicket (5.6 vs. 3% to a depth of 10 cm) and is exceptionally high for a semi-arid region. The potential to sequestrate carbon in degraded thicket landscapes is thus considerable. Managing the land for greater sequestration of C will have the added benefit of increasing soil aggregate stability, reducing the tendency of soils to crust and therefore increasing the rate of water infiltration through the pedoderm. The benefits of such an approach have been recognised by specialists in soil conservation and rural land use for many decades, based largely on empirical observation. The results of this thesis provide a more quantitative basis for appreciating the effects of soil C across a broad spectrum of South African biomes. / AFRIKAANSE OPSOMMING: Die invloed van verskillende landgebruikspraktyke op grondkwaliteit in Suid-Afrika is in vyf kontrasterende biome ondersoek met spesifieke klem op die neiging van gronde om korste te vorm en die grond koolstofinhoud. Grondkwaliteit is 'n vae konsep en die toepassing daarvan in die Suid-Afrikaanse grondlandskap is noukeurig ondersoek. 'n Wye reeks van chemiese en fisiese grondeienskappe is ondersoek. Die neiging van korsvorming by gronde is beraam deur die gebruik van breukmodulus, waterdispergeerbare klei en 'n nuwe metode van laboratorium-infiltrasie wat met behulp van reënvalsimulasie gekontroleer is. Korsvorming was groter in kaal, blootgestelde gronde as in gronde met 'n plantbedekking en het gewissel volgens moedermateriaal. Verskille in korsvorming word verklaar deur faktore wat verband hou met kleidispergering soos byvoorbeeld kleimineralogie, grondkoolstof, labiele of maklik oksideerbare koolstof, konsentrasie oplosbare soute, grondtekstuur en uitruilbare natriumpersentasie (UNP). Resultate van langtermyn brandpersele in savanna en grasland het getoon dat jaarlikse brand die neiging tot korsvorming kan verhoog. Meer korsvorming in brandpersele word toegeskryf aan groter kleidispergering, wat waarskynlik verband hou met 'n afname in grondkoolstof, 'n afname in elektriese geleiding (Be) en 'n toename in UNP. Plantvoedingstowwe gaan oor tyd verlore uit brandpersele, waarskynlik deur die verwydering van as in oppervlak afloop. Kalsium, Mg en K gaan meer geredelik verlore as Na, waarskynlik omdat plante hierdie voedingstowwe in groter hoeveelhede opneem as Na. Die netto effek is 'n toename in UNP. Korsvorming op brandpersele kan self instand gehou word omdat verhoogde afloop die moontlike verlies van oplosbare soute kan verhoog. Verwydering van plantegroei deur bewerking, beweiding of brand het grondkoolstof op alle plekke verlaag. Die gemiddelde grondkoolstof in die 0-1 cm laag van ongebrande persele in die Kruger Nasionale Park was meer as drie maal groter as in --.. brandpersele (2.7 vs 0.8 %). Die verskil in grondkoolstof tussen behandelings neem af met diepte wat daarop dui dat monsterneming tot dieptes groter as 'n paar sentimeters die effek van landgebruik kan verberg. Die boonste paar sentimeters van 'n grond het 'n oneweredige invloed op infiltrasie en voedingstofsirkulasie. Hierdie laag word die pedoderm genoem. Boombedekking op brandperseie in die suidelikeKruger Nasionale Park is hoogs variërend. Die hipotese was dat dit 'n funksie van druk deur planteters is. Planteters neig om op persele met die hoogste klei, Zn- en Mn-inhoud en die laagste boom bedekking te versamel. Daar word voorgestel dat grondeienskappe die hoeveelheid planteters na 'n brand bepaal. Dit beïnvloed op sy beurt weer die boombedekking. In die Oos-Kaap het intensiewe bokboerdery digte bosruigtes verander na oop savannas. Gronde van bok-veranderde lokaliteite het 'n groter neiging tot korsvorming as gronde van onveranderde bosruigtes, vermoedelik as gevolg van verswakking van aggregate met 'n. afname in grondkoolstof. Die gemiddelde grondkoolstof van onveranderde bosruigtes was byna dubbel soveel as die koolstof van bok-veranderde bosruigtes (5.6 vs 3 % tot 'n diepte van 10 cm) en buitengewoon hoog vir 'n semi-ariede streek. Die potensiaal vir koolstof sekwestrasie in degradeerde bosruigte landskappe is dus aansienlik. Bestuur van land vir groter sekwestrasie van koolstof het die bykomende voordeel van verhoogde grond aggregaatstabilteit, verlaging van die neiging tot korsvorming en daardeur 'n verhoging in die tempo van waterinfiltrasie deur die pedoderm. Die voordele van so 'n benadering is vir baie dekades deur spesialiste in grondbewaring en landelike landgebruik herken. Dit was grootliks gebaseer op empiriese waarneming. Die resultate van hierdie tesis bied 'n meer kwantitatiewe basis tot die verstaan van die invloed van grondkoolstof oor 'n breë spektrum van Suid-Afrikaanse biorne.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Concrete evidence of dryland salinity was observed in the Berg River catchment in the Western Cape Province of South Africa. Soil salinization is a global land degradation hazard that negatively affects the productivity of soils. Timely and accurate detection of soil salinity is crucial for soil salinity monitoring and mitigation. It would be restrictive in terms of costs to use traditional wet chemistry methods to detect and monitor soil salinity in the entire Berg River catchment. The goal of this study was to investigate less tedious, accurate and cost effective techniques for better monitoring. Firstly, hyperspectral remote sensing (HRS) techniques that can best predict electrical conductivity (EC) in the soil using individual bands, a unique normalized difference soil salinity index (NDSI), partial least squares regression (PLSR) and bagging PLSR were investigated. Spectral reflectance of dry soil samples was measured using an analytical spectral device FieldSpec spectrometer in a darkroom. Soil salinity predictive models were computed using a training dataset (n = 63). An independent validation dataset (n = 32) was used to validate the models. Also, field-based regression predictive models for EC, pH, soluble Ca, Mg, Na, Cl and SO4 were developed using soil samples (n = 23) collected in the Sandspruit catchment. These soil samples were not ground or sieved and the spectra were measured using the sun as a source of energy to emulate field conditions. Secondly, the value of NIR spectroscopy for the prediction of EC, pH, soluble Ca, Mg, Na, Cl, and SO4 was evaluated using 49 soil samples. Spectral reflectance of dry soil samples was measured using the Bruker multipurpose analyser spectrometer. “Leave one out” cross validation (LOOCV) was used to calibrate PLSR predictive models for EC, pH, soluble Ca, Mg, Na, Cl, and SO4. The models were validated using R2, root mean square error of cross validation (RMSECV), ratio of prediction to deviation (RPD) and the ratio of prediction to interquartile distance (RPIQ). Thirdly, owing to the suitability of land components to map soil properties, the value of digital elevation models (DEMs) to delineate accurate land components was investigated. Land components extracted from the second version of the 30-m advanced spaceborne thermal emission and reflection radiometer global DEM (ASTER GDEM2), the 90-m shuttle radar topography mission DEM (SRTM DEM), two versions of the 5-m Stellenbosch University DEMs (SUDEM L1 and L2) and a 5-m DEM (GEOEYE DEM) derived from GeoEye stereo-images were compared. Land components were delineated using the slope gradient and aspect derivatives of each DEM. The land components were visually inspected and quantitatively analysed using the slope gradient standard deviation measure and the mean slope gradient local variance ratio for accuracy. Fourthly, the spatial accuracy of hydrological parameters (streamlines and catchment boundaries) delineated from the 5-m resolution SUDEM (L1 and L2), the 30-m ASTER GDEM2 and the 90-m SRTM was evaluated. Reference catchment boundary and streamlines were generated from the 1.5-m GEOEYE DEM. Catchment boundaries and streamlines were extracted from the DEMs using the Arc Hydro module for ArcGIS. Visual inspection, correctness index, a new Euclidean distance index and figure of merit index were used to validate the results. Finally, the value of terrain attributes to model soil salinity based on the EC of the soil and groundwater was investigated. Soil salinity regression predictive models were developed using CurveExpert software. In addition, stepwise multiple linear regression soil salinity predictive models based on annual evapotranspiration, the aridity index and terrain attributes were developed using Statgraphics software. The models were validated using R2, standard error and correlation coefficients. The models were also independently validated using groundwater hydro-census data covering the Sandspruit catchment. This study found that good predictions of soil salinity based on bagging PLSR using first derivative reflectance (R2 = 0.85), PLSR using untransformed reflectance (R2 = 0.70), a unique NDSI (R2 = 0.65) and the untransformed individual band at 2257 nm (R2 = 0.60) predictive models were achieved. Furthermore, it was established that reliable predictions of EC, pH, soluble Ca, Mg, Na, Cl and SO4 in the field are possible using first derivative reflectance. The R2 for EC, pH, soluble Ca, Mg, Na, Cl and SO4 predictive models are 0.85, 0.50, 0.65, 0.84, 0.79, 0.81 and 0.58 respectively. Regarding NIR spectroscopy, validation R2 for all the PLSR predictive models ranged from 0.62 to 0.87. RPD values were greater than 1.5 for all the models and RMSECV ranged from 0.22 to 0.51. This study affirmed that NIR spectroscopy has the potential to be used as a quick, reliable and less expensive method for evaluating salt-affected soils. As regards hydrological parameters, the study concluded that valuable hydrological parameters can be derived from DEMs. A new Euclidean distance ratio was proved to be a reliable tool to compare raster data sets. Regarding land components, it was concluded that higher resolution DEMs are required for delineating meaningful land components. It seems probable that land components may improve salinity modelling using hydrological modelling and that they can be integrated with other data sets to map soil salinity more accurately at catchment level. In the case of terrain attributes, the study established that promising soil salinity predictions could be made based on slope, elevation, evapotranspiration and terrain wetness index (TWI). Stepwise multiple linear regressions soil salinity predictive model based on elevation, evapotranspiration and TWI yielded slightly more accurate prediction of soil salinity. Overall, the study showed that it is possible to enhance soil salinity monitoring using HRS, NIR spectroscopy, land components, hydrological parameters and terrain attributes. / AFRIKAANSE OPSOMMING: Konkrete bewyse van droëland sout is waargeneem in die Bergrivier opvanggebied in die Wes- Kaap van Suid-Afrika. Verbrakking van grond is 'n wêreldwye probleem wat ‘n negatiewe invloed op die produktiwiteit van grond kan hê. Tydige en akkurate herkenning van verandering in grond soutgehalte is ‘n noodsaaklike aksie vir voorkoming. Dit sou beperkend wees in terme van koste om konvensionele nat chemiese metodes te gebruik vir die opsporing en monitering daarvan in die hele Bergrivier opvanggebied. Die doel van hierdie studie was om ondersoek in te stel na minder tydsame, akkurate en koste-effektiewe tegnieke vir beter monitering. Eerstens, is hiperspektrale afstandswaarnemings (HRS) tegnieke wat die beste in staat is elektriese geleidingsvermoë (EG) in die grond te kan voorspel deur gebruik te maak van individuele bande, 'n unieke genormaliseerde grond soutindeks verskil (NDSI), parsiële kleinste kwadratiese regressie (PLSR) en afwyking in PLSR, is ondersoek. Spektrale reflektansie van droë grondmonsters is gemeet deur gebruik te maak van 'n spektrale analitiese toestel: FieldSpec spektrometer in 'n donkerkamer. Voorspellings modelle vir grond soutgehalte is bereken met behulp van 'n toets datastel (n = 63). 'n onafhanklike validasie datastel (n = 32) is gebruik om die modelle te evalueer. Daarbenewens is veld-gebaseerde regressie voorspellings modelle vir EG, pH oplosbare Ca, Mg, Na, Cl and SO4 ontwikkel deur gebruik te maak van grondmonsters (n = 23) versamel in the Sandpruit opvangsgebied. Hierdie grondmonsters is nie gemaal of gesif nie en die spectra is gemeet deur gebruik te maak van die son as ‘n bron van energie om veld toestande na te boots. Tweedens, is die waarde van NIR spektroskopie vir die voorspelling van die EG, pH, oplosbare Ca, Mg, Na, Cl, en SO4 met behulp van 49 grondmonsters geëvalueer. Spektrale reflektansie van droë grondmonsters is gemeet deur gebruik te maak van die Bruker NIR veeldoelige analiseerder . Kruisvalidering (LOOCV) is gebruik om PLSR voorspellings modelle vir EG, pH, oplosbare Ca, Mg, Na, Cl, en SO4 te kalibreer. Hierdie modelle is gevalideer: R2, wortel-gemiddelde-kwadraat fout kruisvalidering (RMSECV), verhouding van voorspellings afwyking (RPD) en die verhouding van die voorspelling se inter-kwartiel afstand (RPIQ). Derdens is land komponente gekarteer vanweë die nut daat van tov grondeienskappe, en die waarde van DEMs is ondersoek om akkurate land komponente af te baken. Land komponente uit die tweede weergawe van die 30 m gevorderde ruimte termiese emissie en refleksie radio globale DEM (ASTER GDEM2), die 90-m ruimtetuig radar topografie sending DEM (SRTM DEM), twee weergawes van die 5 m Universiteit van Stellenbosch DEMs (SUDEM L1 en L2) en 'n 5 m DEM (GEOEYE DEM) afgelei van GeoEye stereo-beelde, is vergelyk. Land komponente is afgebaken met behulp van helling, gradiënt en aspek afgeleides van elke DEM. Die land komponente is visueel geïnspekteer en kwantitatief ontleed met behulp van die helling gradiënt standaardafwyking te meet en die gemiddelde helling-gradiënt-plaaslike variansie verhouding vir akkuraatheid. Vierdens, is die ruimtelike akkuraatheid van hidrologiese parameters (stroomlyn en opvanggebied grense) geëvalueer soos afgelei vanaf die 5 m resolusie SUDEM (L1 en L2), die 30 m ASTER GDEM2 en die 90 m SRTM . Die verwysings opvanggebied grens en stroomlyn is gegenereer vanaf die 1,5-m GEOEYE DEM. Opvanggebied grense en stroomlyn uit die DEMs is bepaal deur gebruik te maak van die Arc Hydro module in ArcGIS. Visuele inspeksie, korrektheid indeks, 'n nuwe Euklidiese afstand indeks en die indikasie-van-meriete indeks is gebruik om die resultate te valideer. Laastens is die waarde van die terrein eienskappe om grond southalte te modeleer ondersoek, gebaseer op die EG van die grond en grondwater. Grond soutgehalte regressie voorspellings modelle is ontwikkel met behulp van CurveExpert sagteware. Verder, stapsgewyse meervoudige lineêre regressie grond soutgehalte voorspellings modelle gebaseer op jaarlikse evapotranspirasie, die dorheids indeks en terrein eienskappe is ontwikkel met behulp van Statgraphics sagteware. Die modelle is gevalideer deur gebruik te maak van R2, standaardfout en korrelasiekoëffisiënte. Die modelle is ook onafhanklik bekragtig deur die gebruik van grondwater hidro-sensus-data wat die Sandspruit opvanggebied insluit. Hierdie studie het bevind dat 'n goeie voorspelling van grond soutgehalte gebaseer op uitsak PLSR met behulp van eerste orde afgeleide reflektansie (R2 = 0,85), PLSR deur gebruik te maak van ongetransformeerde reflektansie (R2 = 0,70), 'n unieke NDSI (R2 = 0,65) en die ongetransformeerde individuele band op 2257 nm (R2 = 0,60) voorspellings modelle verkry is. Verder is vasgestel dat betroubare voorspellings van die EG, pH, oplosbare Ca, Mg, Na, Cl en SO4 in die veld moontlik is met behulp van eerste afgeleide reflektansie. Die R2 van EG, pH, oplosbare Ca, Mg, Na, Cl en SO4 is 0.85, 0.50, 0.65, 0.84, 0.79, 0.81 en 0.58 onderskeidelik. Ten opsigte van NIR spektroskopie het die validasie van R2 vir al die PLSR voorspellings modelle gewissel tussen 0,62-0,87. Die RPD waardes was groter as 1,5 vir al die modelle en RMSECV het gewissel tussen 0,22-0,51. Hierdie studie het bevestig dat NIR spektroskopie die potensiaal het om gebruik te word as 'n vinnige, betroubare en goedkoper metode vir die analise van soutgeaffekteerde gronde. T.o.v. hidrologiese parameters, het die studie tot die gevolgtrekking gekom dat waardevolle hidrologiese parameters afgelei kan word uit DEMs. 'n nuwe Euklidiese afstand verhouding is bevestig as 'n betroubare hulpmiddel om raster datastelle te vergelyk. Ten opsigte van grond komponente, is daar tot die gevolgtrekking gekom dat hoër resolusie DEMs nodig is vir die bepaling van sinvolle land komponente. Dit lyk waarskynlik dat die land komponent soutgehalte modellering hidrologiese modellering verbeter en dat hulle geïntegreer kan word met ander datastelle vir meer akkurate kaarte op opvangsgebied skaal. In die geval van die terrein eienskappe het, die studie vasgestel dat belowende grond soutgehalte voorspellings gemaak kan word gebaseer op helling, elevasie, evapotranspirasie en terrein natheid indeks (TWI). 'n stapsgewyse meervoudige lineêre regressie grond soutgehalte voorspellings model wat gebaseer is op elevasie, evapotranspirasie en TWI het effens meer akkurate voorspellings van die grond soutgehalte gelewer. In geheel gesien, het die studie getoon dat dit moontlik is om grond soutgehalte monitering te verbeter met behulp van HRS, NIR spektroskopie, land komponente, hidrologiese parameters en terrein eienskappe. / The Agricultural Research Council (ARC), Water Research Commission and the National Research Foundation for funding.