Theses and Dissertations
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Browsing Theses and Dissertations by Author "Araya, H. E."
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Item Embargo Evaluating rhizosphere soil microbes, grain yield and nutritional composition of two legume species in farmers' fields in four Municipalities of Vhembe district.(2024-09-06) Matidze, A.; Ogola, J. B. O.; Mokgehle, S. N.; Araya, H. E.Despite the nutritional value and the amounts of N that legumes contribute to the soil, few studies have evaluated rhizosphere soil microbes, grain yield and nutritional composition of indigenous legumes in the fields of South African farmers. To explore the variations in grain yield, rhizospheres soil microbes and nutritional composition in Bambara groundnut and cowpea species, this study evaluated two legume species under five farmer's fields conditions at four locations (Thulamela, Musina, Makhado and Collin Chabane) in the Vhembe district regions of Limpopo province, South Africa during the 2021/2022 summer cropping season. Ten of each Bambara groundnut and cowpea were sampled at 75% physiological maturity from each farmers’ field to determine growth yield and yield components, nutritional composition, and mineral content variations. Ca, K, Mg, Na, B, Cu, Fe, Zn, and protein levels were determined in ground pods and leaves. The rhizosphere soil samples were from 15 cm soil depth. Soil microbial diversity was determined using Carbon Source Utilisation Profiles (CSUP) BIOLOG™ GN2 plates. The abundance and richness of the soil microbes were also determined using the Shannon-Weaver and Evenness diversity indices. The collected data showed significant (p≤0.05) differences in plant dry matter (DM) yield, number of pods, pods dry weight and number of nodules from different farmer’s fields. The high temperature reported in Musina, which exhibited higher growth and yield for Bambara groundnut compared to the other municipalities, indicates the different sites' climatic conditions. A positive correlation was observed between monthly maximum temperature and dry matter for Bambara groundnut (r2 =0.33) and cowpea (r2=0.30). In Makhado municipality, the data showed increased dry matter (144.3 g/plant) and the least in Musina (68.3 g/plant). The legume species studied exhibited differences in the grain protein fractions' profile and grain mineral content. The two species grains showed considerable significant variation for the following nine mineral contents (mg/g dry matter) obtained for the micro minerals of Bambara groundnut Na 897 mg/kg, Fe 534 mg/kg and Zn 35 mg/kg. Cowpea Na 219 mg/kg, Zn 45 mg/kg, and B 31 mg/kg, and for the macro minerals: Bambara groundnut K 1.55 mg/kg, Ca 0.16 mg/kg, Mg 0.21 mg/kg, P 0.26 mg/kg. Cowpea K 1.30 mg/kg, Ca 0.21 mg/kg, Mg 0.25 mg/kg, and P 0.36 mg/kg. The significant difference in Shannon Weaver Diversity Index (H’) (i.e., the ability of the microbial community to degrade more or fewer types of carbon sources at a threshold ODi value ≥ 0.25) was observed for samples in cowpea species under Makhado location, which could degrade more types of carbon sources. Statistically significant utilisation was detected for all five groups of carbon sources. The microbial communities detected the highest AWCD for utilising all carbon sources (carbohydrates, carboxylic acids, amino acids, polymers and amines). This soil diversity and richness is an indicator of the quality of the soil to increase crop yields and agricultural production. Additional research is needed to determine the microbial diversity and activity yield variations, nutritional composition, and mineral elements of Bambara groundnut and cowpea species.