The role of ferrolysis in the genesis of selected soils of the Eastern Free State
| dc.contributor.advisor | Le Roux, P. A. L. | |
| dc.contributor.advisor | Du Preez, C. C. | |
| dc.contributor.author | Macheli, Malerata Suzan | |
| dc.date.accessioned | 2018-01-24T06:55:33Z | |
| dc.date.available | 2018-01-24T06:55:33Z | |
| dc.date.issued | 2007-11 | |
| dc.description.abstract | English: Plinthic and duplex soil forms make up a substantial part of the soils under cultivation in South Africa. The tendency of these soils to occur either in isolation, or in association with one another, leaves the impression that ideal conditions for the formation of each occur independently but are closely related. This implies that ideal conditions for the development of each vary over short distances. Little research has been done on the duplex-plinthic soil association but a relationship between the two soil groups is implied in literature. A proper understanding of soil genesis may therefore contribute to the better classification, interpretation and evaluation of these soils for sustainable land-use purposes. The hypothesis is that the redistribution of Fe-Mn and degradation of silicate clays are important processes involved in the formation of soils with either a duplex or plinthic character. The objective of the study was to establish the role of ferrolysis and redistribution of Fe-Mn in the genesis of the duplex-plinthic soil association. The catena concept; which describes a sequence of soils of about the same age, occurring under similar macroclimatic conditions and derived from the same parent material; but with different characteristics due to variation in topography and drainage; was adopted. A toposequence of 10 representative profiles was selected in the Eastern Free State. The soils were described, sampled and photographed. Representative composite and undisturbed samples were analysed for several chemical, physical and morphological soil properties. The selected toposequence commences at the crest with a profile of the Hutton soil form. Soils of the Westleigh, Longlands, Avalon (3), Kroonstad (3) and Estcourt forms follow down slope. The characteristic red colour grades to yellow-brown in the soft plinthic soils on the mid slope and grey duplex soils in the valley bottom. The change in colour dominates morphology in the midslope but changes to be dominated by texture differentiation in the valley bottom. Signs of redox activity prevail across the toposequence and its prominence increases drastically with depth in the profiles and down slope in the catena. Subsoil acidification indicates the presence of an early stage of redox activity. Fe-Mn redistribution, present as mottles and concretions, and colour changes are indications of intermediate redox activity. The texture differentiation present indicates an environment supporting ferrolysis to the full. | en_ZA |
| dc.description.abstract | Afrikaans: Plintiese in dupleks grondvorms maak ‘n groot deel van die gronde onder bewerking uit in Suid-Afrika. Die tendens van hierdie gronde om in isolasie of in assosiasie met makaar voor te kom laat die indruk dat die ideale toestande vir die vorming van elk onafhanklik voorkom maar nou verwant is. Dit impliseer dat ideale toestande vir die ontwikkeling van gronde ook kort afstande varieer. Min navorsing is gedoen op die dupleks-plintiet grondassosiasie maar die verband word geïmpliseer in die literatuur. ’n Goeie begrip van die genese van die gronde kan daarom bydra tot verbeterde klassifikasie, interpretasie en evaluering van hierdie gronde vir volhoubare landgebruik. Die hipotese is dat die herverspreiding van Fe-Mn en die degradasie van silikaatklei belangrike prosesse in die vorming van gronde met dupleks of plintiese karakter is. Die doel van die studie was om die rol van ferrolise en herverspreiding van Fe-Mn in die genese van die dupleks-plintiet grondassosiasie vas te stel. Die katena konsep nl. ’n volgorde van gronde van ongeveer dieselfde ouderdom wat in soortgelyke makroklimaat toestande voorkom en ontstaan het uit dieselfde moedermateriaal maar met verskillende kenmerke wat die gevolg van variasie in topografie is, is aanvaar. ’n Toporeeks van 10 verteenwoordigende profiele is geselekteer in die Oosvrystaat. Die gronde is beskryf, gemonster en gefotografeer. Verteenwoordigende saamgestelde en onversteurde monsters is ontleed vir verskeie chemiese, fisiese en morfologiese grondeienskappe. Die geselekteerde toporeeks begin op die kruin met ’n profiel van die Huttongrond. Gronde van die Westleigh, Longlands, Avalon (3), Kroonstad (3) en Estcourt vorms volg bult af. Die kenmerkende rooi kleur gradeer na geel-bruin in die middelhang en grys dupleksgronde in die valeivloer. Kleurverandering domineer die morfologie in die middelhang maat dit verander en word oorheers deur tekstuur differensiasie in die valleivloer. Tekens van redoksaktiwiteit kom oor die toporeeks voor en die prominensie neem toe afwaarts in profiele en afwaarts in die katena. Ondergrond versuring dui die teenwoordigheid van ’n vroeë stadium van redoksaktiwiteit aan. Fe-Mn herverspreiding, teenwoordig as vlekke en konkresies, en kleur veranderinge, is aanduidings van ‘n intermediêre termyn van redoksaktiwiteit. Die tekstuurverskille wat in duplexgronde voorkom dui op ’n omgewing waar ferrolise ten volle aktief is. | af |
| dc.identifier.uri | http://hdl.handle.net/11660/7689 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Plinthic and duplex soils | en_ZA |
| dc.subject | Redox conditions | en_ZA |
| dc.subject | Ferrolysis | en_ZA |
| dc.subject | Fe-Mn redistribution | en_ZA |
| dc.subject | Toposequence | en_ZA |
| dc.subject | Colour | en_ZA |
| dc.subject | Mottling | en_ZA |
| dc.subject | Concretions | en_ZA |
| dc.subject | Texture differentiation (morphology) | en_ZA |
| dc.subject | Soil formation -- South Africa -- Free State | en_ZA |
| dc.subject | Soil texture -- South Africa -- Free State | en_ZA |
| dc.subject | Metals -- Absorption and desorption | en_ZA |
| dc.subject | Soil absorption and desorption | en_ZA |
| dc.subject | Dissertation (M.Sc.Agric. (Soil, Crop and Climate Sciences))--University of the Free State, 2007 | en_ZA |
| dc.title | The role of ferrolysis in the genesis of selected soils of the Eastern Free State | en_ZA |
| dc.type | Dissertation | en_ZA |