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Fwanyanga, Felicitas Mantjodi 2023-10-27T13:49:57Z 2023-10-27T13:49:57Z 2023 http://hdl.handle.net/11070/3752 A thesis submitted in fulfilment of the requirements for the degree of master of science in microbiology in biological sciences Bambara groundnut (Vigna subterranea (L.) Verdc) is the third most significant food legume in Africa after groundnut (Arachis hypogea) and cowpea (Vigna unguiculata). It is normally grown in poor soils, is drought tolerant, and has a high potential for nitrogen fixation. Despite that, Bambara groundnut yields are on a gradual decline due to a combination of abiotic and biotic stresses such as erratic annual rainfall and climate induced changes in soil microbial community compositions, which negatively impacting food security. Thus, the application of rhizobial inoculants at planting significantly improves yields in many leguminous crops. Moreover, symbiotic inoculants are mainly used in developed countries to improve nitrogen fixation and improve productivity of grain legumes. Sub-Saharan African countries like Namibia, however, still under-utilise the above practice. Three (3) studies were conducted, of which two were conducted in 2021, and in 2021/22 season. The first study was on farmer’s appraisal, which was aimed to assess Bambara groundnut production systems in Kavango East Region. Bambara groundnut farming systems, farming inputs, and production constraints were explored in the two constituencies in Kavango East region. Subsequently, an experiment in a greenhouse of the ZERI at the University of Namibia using soil from the Kavango region to ascertain how well the various Bradyrhizobium strains promote nodulation and yield components among three varieties of Bambara groundnut was conducted. The study also evaluated the strains that are most competitive to reach the roots and promote nodulation in a given period. For the greenhouse experiment, the treatments included three different Bambara groundnut varieties that were inoculated with two types of inoculants (MIX inoculant with 7 Bradyrhizobium strains [1-7; 3B 4-1; 9-5, 36 1-1; 36 3-2; 55 1-1 and 60 2-1] and inoculant with Bradyrhizobium vignae 9-5 only), both of which were obtained from the University of Bremen in Germany the third treatment was an absolute control. The treatments were set up in a randomized complete block design with three replications. In comparison to the single strain 9-5, the mixed strains were found to be more productive and contagious (p=0.05). Moreover, the two inoculants outperformed the non-inoculated cultivars in terms of plant height, shoot dry weight. The brown variety, which was not inoculated, nevertheless, showed some nodules. Hence, in the next season (field ii experiment) the mixed inoculant strains of Bradyrhizobium were applied as single inoculants. The field experiment was conducted at Mashare Agricultural Development Institute (MADI) in Kavango East Region. The same three Bambara groundnut varieties which were used in the greenhouse were treated with chemical fertilizer (urea), 7 Bradyrhizobium strains, and negative control with no treatment. After 130 days of planting the cultivars were harvested and different yield parameters were assessed. The control Var03 (red) yielded the greatest grain at 1311.7 kg ha-1 , followed by Var01 (brown) treated with In1-7 at 1237.3kg ha-1 , while Var01 and Var02 (cream) inoculated with In36 3-2 yielded 1171.3kg ha-1 each. Based on the results, farmers are advised to consider inoculating Bambara groundnut seeds with Bradyrhizobium strains prior to planting, as this has been shown to have a positive impact on nodulation, grain yield, and biomass production compared to using urea fertilizer which is expensive and environmentally unfriendly. However, it is important to note that the control variety Var03 performed the best, likely due to its compatibility with native soil rhizobia. Therefore, it may be worthwhile for more studies to investigate and identify the unidentified strains used in the study as potential bio-inoculants. Additionally, it is recommended that farmers monitor the performance of different varieties in their specific soil conditions and choose the most suitable one for their crop management. Finally, it is important to adhere to best practices for inoculant application, such as using high-quality inoculants and ensuring proper handling and storage en University of Namibia Bambara groundnuts Biofertiliser Bradyrhizobia Food security Legumes (Fabaceae) Productivity Rhizobia inoculant effects on bambara groundnut growth and yield in Namibia Thesisopen.access