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dc.contributor.advisorClaassens, S.
dc.contributor.advisorFourie, D.
dc.contributor.authorJansen, Chantelle
dc.date.accessioned2015-02-12T06:31:16Z
dc.date.available2015-02-12T06:31:16Z
dc.date.issued2014
dc.identifier.urihttp://hdl.handle.net/10394/13339
dc.descriptionMSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014en_US
dc.description.abstractSoil is an important ecosystem that supports a wide variety of organisms such as bacteria, fungi, arthropods and nematodes. This sensitive ecosystem may be influenced by various factors, including agricultural management practices. With the introduction of genetically modified (GM) glyphosate-tolerant (RoundUp ® Ready: RR) crops, herbicides such as glyphosate have been increasingly used. However, little is known about the effect of glyphosate on the biological communities in these herbicide-sprayed soils. With the intimate proximity that microorganisms and nematodes have with the roots of plants, these organisms can be used to assess changes that may occur in the soil surrounding roots of RR crops. The aim of this study was to determine microbial community structure and nematode diversity, with emphasis on that of non-parasitic nematodes, in soil samples from conventional soybean (CS) - and RR- soybean fields compared to that in adjacent natural veld (NV) areas. Samples were collected from twenty three sites at six localities that are situated within the soybean-production areas of South Africa. These sites represented fields where RR and CS soybean grew, as well as surrounding NV. All RR fields have been treated with glyphosate for no less than five years. Microbial community structures of the twenty three sites in the RR, CS and NV ecosystems were determined by phospholipid fatty acid (PLFA) analyses. Nematode diversity was determined by extracting the nematodes from soil samples and conducting a faunal analysis. Soil physical and chemical properties were determined by an independent laboratory, Eco-Analytica (North West University, Potchefstroom) according to standard procedures. Results from this study indicated differences in microbial community structure between the various localities. However, there were no significant (p ≤ 0.05) differences in microbial community structures between RR- and CS ecosystems. Soils of both RR- and CS crops were primarily dominated by bacteria. Nematode identification and faunal analysis also indicated no significant (p ≤ 0.05) differences between the different non-parasitic/beneficial nematodes that were present in soils of these two ecosystems during the time of sampling. Non-parasitic nematode communities were primarily dominated by bacterivores. A faunal analysis indicated that most of the sites contained enriched, but unstructured soil food-webs. However, four of the sites showed enriched and structured food webs due to the presence of non-parasitic nematodes with high coloniser-persister (cp) values. Relationships between non-parasitic nematode – and microbial communities showed that there was a positive relationship between nematode functional groups and their corresponding microbial prey. From the results obtained in this study, it can be concluded that the community structures of both non-parasitic nematodes and microorganisms shared similarities. These community structures showed no long-term detrimental effects of glyphosate application in the soils surrounding roots of RR soybean crops. Relationships existed between non-parasitic nematode and microbial communities in the rhizosphere of soybean crops and natural veld. For example, bacterivore nematodes had a strong positive relationship with gram-negative bacteria. Similar but weaker relationships also existed between carnivores, omnivores, plantparasitic nematodes and gram-negative bacteria. A positive relationship also existed between fungivores and fungal fatty acids. This emphasises the value of these organisms as indicators of soil health and also the impact that agricultural practices can have on soils.en_US
dc.language.isoenen_US
dc.subjectConventional soybean (CS)en_US
dc.subjectFaunal analysisen_US
dc.subjectGenetically-modifieden_US
dc.subjectGlyphosateen_US
dc.subjectMicrobial community structureen_US
dc.subjectNematode diversityen_US
dc.subjectPhospholipid fatty acid (PLFA) analysesen_US
dc.subjectRoundUp ® Ready (RR) soybeanen_US
dc.subjectFauna analisesen_US
dc.subjectFosfolipidvetsuur (PLFA) analiseen_US
dc.subjectGeneties-gemodifiseerdeen_US
dc.subjectGlifosaaten_US
dc.subjectKonvensionele sojaboon (CS)en_US
dc.subjectMikrobiese gemeenskapstruktuuren_US
dc.subjectNematooddiversiteiten_US
dc.subjectRoundUp ® Ready (RR) sojaboonen_US
dc.titleMicrobial community structure and nematode diversity in soybean-based cropping systemsen
dc.typeThesisen_US
dc.description.thesistypeMastersen_US
dc.contributor.researchID11935952 - Claassens, Sarina (Supervisor)


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