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dc.contributor.advisorLouw, S. vd M.
dc.contributor.authorSmith, Jehane
dc.date.accessioned2016-10-14T14:14:13Z
dc.date.available2016-10-14T14:14:13Z
dc.date.issued2016
dc.identifier.urihttp://hdl.handle.net/11660/4217
dc.description.abstractEnglish: Integrated methods in land use and land management are needed, in addition to traditional agricultural practices, to provide an increasing human population with the necessary food security. By conserving soil organisms in crop agro-ecosystems, farmers can in essence be practicing sustainable conservation agriculture, where soil biodiversity is responsible for soil health. Potential toxic plants, whether natural (allelopathic) or anthropogenic (GMOs), cause a concern regarding this biodiversity in agro-ecosystems. Maize that has been genetically engineered using the soil bacterium Bacillus thuringiensis (Bt), known as Bt maize, expresses the synthetically modified Cry1Ab, Cry1F, Cry1A.105 or Cry2Ab2 proteins that are toxic to some insects. The impact of Bt-maize on non-target soil organisms is an important aspect in soil health and agricultural sustainability. The same goes for allelopathic crops, which can influence other crops in their immediate vicinity or in succeeding seasons. The aims of this study were to determine the possible effects of GMOs (Bt-maize), allelopathic crops (alfalfa and sunflower) and aromatic crops (onion) on soil meso-arthropod assemblages. A trial on humus decomposition rates and the potential occurrence of a Home field advantage (HFA) of decomposing litter was also conducted, the relevance being that decomposition is the driver of soil organic matter (SOM) production which enriches soil and, in turn, benefits soil organisms. Soil samples were taken at the roots of the plants in the porosphere where the plant interacts directly with its environment. To extract soil mesofauna, the Tullgren extraction method was used. Samples were collected from the following localities in the Free State: Bainsvlei area (maize, onion, and decomposition samples on the farm Geluk), Bainsvlei area (alfalfa and decomposition samples on the farm Maranatha), Bloemdal area (maize – on the farms Karee Laagte and Feather Stone) and Petrusburg area (sunflower and onion – on the farm Thornberry). To analyse data statistically, the Shannon diversity index, Sørensen similarity index and Home field advantage index (HFAI) was used. No immediate negative effects of Bt maize on soil faunal diversity were observed. However, in a 2012 study, a higher diversity of soil mesofauna was observed in the Bt fields, indicating that plants with the insect resistant gene may very well benefit soil faunal groups due to increased plant health and production of a larger root mass (podosphere). The influence of allelopathic crops on soil meso-arthropods showed that stressed allelopathic plants had an overall lower diversity than non-stressed plants. However, there is some uncertainty here, since lower diversity can also be attributed to low soil humidity and exposure to external post-harvest factors during the trial. Overall diversity in onion fields was lower than in the control fields, whilst some species of soil organisms only occurred in the natural fields and not in the onion field. There was no indication that the toxins produced from these plants actually kill the soil fauna, but the assumption could be made that onion plants were at least repellent. Certain mesofaunal species specifically occurred only in the onion fields, indicating opportunism and resistance towards onion repellent odours. The different sampling methods used in the decomposition trial showed some filtering effect in terms of the organisms allowed into the traps. The HFAI patterns for the four successive sampling dates (16, 24, 30 April and 07 May 2014) temporally correlate with the abundance of soil arthropods within the litter traps and litterbags at the given sampling date. Noteworthy during this trial is that certain trophic groups, such as microbes and predators, fulfil a vital role in decomposition and that this process is not only dependant on the litter producing plants as such. Furthermore, allelopathic alfalfa litter was seemingly also preferred by certain introduced, opportunistic collembolan species, indicating the important role alien species can play in the soil environment. In spite of all this and albeit that the sampling methods used in this trial created an unnatural scenario (to a certain degree) for litter decomposition agents by excluding certain size groups of soil arthropods, the overall conclusion is that a HFA (to a certain extent) was confirmed and demonstrated across all the sampling methods used for this short-term decomposition study. All of these aspects in crop agriculture can play a significant role in determining soil fertility and productivity. A better understanding of these processes can provide farmers with the necessary expertise and knowledge to manage sustainable crop farming systems.en_ZA
dc.description.abstractAfrikaans: Geïntegreerde metodes in die gebruik van land en grondbestuur word, tesame met tradisionele landboupraktyke, benodig om 'n toenemende menslike bevolking met die nodige voedselsekuritiet te voorsien. Deur die bewaring van grond biodiversiteit in gewas agro-ekostelsels kan boere volhoubare landbou-bewaring toepas, en sodoende die grond organismes wat verantwoordelik is vir grondgesondheid bewaar. Potensiële giftige plante, of dit nou natuurlik (allelopatiese) of antropogenies (GMOs) is, veroorsaak kommer oor biodiversiteit in agro-ekostelsels. Mielies wat geneties gemanipuleer is, met behulp van Bacillus thuringiensis (Bt), staan bekend as Bt-mielies en stel die sinteties veranderde Cry1Ab, Cry1F, Cry1A.105 of Cry2Ab2 proteien vry wat toksies is vir sekere insekte. Die impak van Bt-mielies op nie-teiken grondorganismes is 'n belangrike aspek in grond gesondheid en volhoubare landbou. Dieselfde geld vir die allelopatiese gewasse wat ander plante rondom hulle, of in daaropvolgende seisoene kan beïnvloed. Die doelwitte van hierdie studie was om die moontlike gevolge van GMO (Bt-mielies), allelopatiese (lusern en sonneblomme) en aromatiese gewasse (uie) op grond meso-geleedpotiges te bepaal. ‘n Proef op die ontbindingstempos en die moontlike voorkoms van 'n tuisveldvoordeel vir ontbindende humus is ook uitgevoer om die ontbindingsproses as drywer van organiese materiaal produksie in grond te beklemtoon. Die proses verryk grond en bevoordeel vervolgens grondorganismes. Grondmonsters is by die wortels van die plante in die porosfeer, waar die plant in direkte kontak met sy omgewing is, geneem. Mesofauna is met behulp van die Tullgren ekstraksie tegniek ge-ekstraeer. Monsters is op die volgende lokaliteite in die Vrystaat versamel: Bainsvlei area (mielies, uie, en ontbinding materiaal op die plaas Geluk), Bainsvlei area (lusern en ontbinding materiaal op die plaas Maranatha), Bloemdal omgewing (mielies op die plase Karee Laagte en Feather Stone) en Petrusburg area (sonneblom en uie op die plaas Thornberry). Om data statisties te ontleed is die Shannon’s diversity index, Sørensen similarity index en Home field advantage index (HFAI) gebruik. Geen onmiddellike negatiewe uitwerking van Bt-mielies op die grondfauna diversiteit was opgemerk nie. Daarenteen was 'n hoër diversiteit van grondmesofauna in die 2012 studie in die Bt velde opgemerk, wat aandui dat plante wat die insekbestande gene bevat grondfauna groepe kan bevoordeel as gevolg van verhoogde plant gesondheid en dus die vorming van 'n groter wortelmassa (porosfeer). Die invloed van allelopatiese gewasse op die grond meso-geleedpotiges het getoon dat onderdrukte allelopatiese plante 'n algehele laer diversiteit toon as nie-onderdrukte plante. Hierdie verskynsel kan egter ook toegeskryf word aan lae grond humiditeit en blootstelling aan eksterne na-oes faktore wat gedurende die proef ondervind is. Algehele diversiteit in uie-lande was laer as in die kontrole lande en sommige grondorganisme spesies was slegs in die natuurlike land en nie in die uie-land versamel nie. Daar was geen aanduiding dat die gifstowwe wat hierdie plante produseer tot grondfauna mortaliteit lei nie, maar dit kan aanvaar word dat uie plante ten minste afwerend was. Sekere spesies het slegs in die uie-lande voorgekom, wat dui op opportunisme en weerstandbiedendheid teenoor uie se afwerende reuke. Die verskillende versamelmetodes in die ontbindingstudie het 'n aantal grondfauna spesies in terme van die toegangklikheid tot die lokvalle gefiltreer. Die HFAI patrone vir die vier agtereenvolgende versameldatums (16, 24, 30 April en 7 Mei 2014) toon temporale korrelasie met die volopheid van grond-geleedpotiges binne die humus-lokvalle en humus-sakke tyens die gegewe versameldatum. Noemenswaardig is dat sekere trofiese groepe, soos mikrobes en predatore, ‘n belangrike rol vervul in ontbinding en dat hierdie proses nie alleenlik van die plant materiaal van die betrokke plante afhang nie. Nietemin, ten spyte hiervan en alhoewel die versamelmetodes wat in die proef gebruik is in ‘n sekere mate 'n onnatuurlike voorstelling van die ontbindingsagente van humusmateriaal geskep het deur sekere grond-geleedpotige grootteklasse uit te sluit, was die algemene gevolgtrekking tog dat 'n tuisveldvoordeel in ‘n sekere mate plaasgevind het oor al die versamelmetodes wat vir hierdie korttermyn ontbindingstudie gebruik is. Al hierdie aspekte kan in landbou 'n belangrike rol in die bepaling van grondvrugbaarheid en produktiwiteit vervul. 'n Beter begrip van hierdie prosesse kan aan boere die nodige kundigheid en kennis verskaf om volhoubare gewasboerdery stelsels te bestuur.af
dc.description.sponsorshipStrategic Academic Cluster, University of the Free Stateen_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectDissertation (M.Sc. (Zoology and Entomology))--University of the Free State, 2016en_ZA
dc.subjectGenetically modified foodsen_ZA
dc.subjectBiodiversity conservationen_ZA
dc.subjectFood securityen_ZA
dc.subjectAllelopathyen_ZA
dc.subjectAeromatic plantsen_ZA
dc.titleInfluence of GM crops, aromatic crops, allelopathy and litter decomposition on species assemblages of meso-arthropods in cultivated soils of the Free State Province, South Africaen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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