| dc.description.abstract | Microorganisms and their interactions in the soil play a critical role in nutrient transformations and cycling, and in sustaining soil productivity. Arbuscular mvcorrhizal fungi (AMF) play a mzgor role in nutrient cycling. Phosphate solubilizing bacteria (PSB) on the other hand play a role in phosphorus nutrition by enhancing its availability to plants through release from inorganic and organic soil phosphorus pools by solubilization and mineralization Activity and composition of microorganisms in soil are influenced by management practices such as the choice of crop species and fertilization. Application of AMF in sweetpotato production can contribute to increased growth, increased yields and improved soil nutrition with a reduction in chemical fertilizer input in a more sustainable agriculture In this study, pot and field experiments were conducted after assessing the dependency of sweetpotatoes to AMF to determine the effects of dual AMF and Phosphate Solubilizing Bacteria (PSB) inoculants with varying rates of chemical phosphorus fertilizer on growth, yield and soil in sweetpotato production. A pot experiment was conducted under greenhouse conditions to evaluate the effects of dual inoculants on Orange Fleshed Sweetpotato (OFSP) growth, yield and nutrition using varieties SPK004 and Kabode as the test crops The commercial inocula were separate single species of Glomus mosseae, Glomus etumcatum and Glomus intraradices in granular formulation containing spores, root fragments and other propagules The indigenous inoculum was a single strain of Glomus aggregatum Local PSB isolates were Azotobacter chrooccocum and Pseudomonas fluorescens. Triple super phosphate (TSP) fertilizer was used at varying rates of OkgP/ha, 20kgP/ha and 40kgP/ha. Varieties responded differently to the different fertilizer rates and AMF inoculation. PSB inoculation did not show any significant effect on the parameters
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assessed (P>0.05). SPK004 had better growth and vine yield compared to Kabode and dry matter yield increased with the application of fertilizer at a rate of 40kgP/ha (2.11 Ot/ha and 0.736t/ha) for shoot and root dry matter yield respectively. In terms of AMF root colonization, the mixed inoculum recorded a higher frequency of 30.72% and intensity of 17.36% that was in line with a highest spore count of 5.40 The single species inoculums gave had a spore recovery of 5.02 and 4.45 spores for GL intraradices and Gl. mosseae respectively. Results of the field experiment showed that the varieties differed significantly in growth (P<0.05) with SPK004 giving a vine yield of 29.17t/ha compared to Kabode with 19.38t/ha However. Kabode had better root yield (14.18t/ha) and SPK004 (12.79t/ha). In terms of AMF colonization, the mixed inoculum gave a 52.22% frequency of colonization that resulted from a higher spore count of 10.94 spores. With the single species inoculants, Gl. intraradices out-performed the other single inoculum with a frequency of 42.04% closely followed by Gl mosseae (42.00%). Increased chemical P fertilization inhibited AMF colonization and the benefits associated with it Mycorrhizal inoculation significantly (P<0.05) influenced root colonization and AMF spore counts recovered in the soil. The highest colonization of 72 78% was in AM inoculated plants in combination with TSP at a rate of 20kgP/ha The highest spore number of 14.83 was observed in mixed AM inoculated plant with 20kgP/ha fertilization. Gl. intraradices was the best performing single species in terms of growth promotion and root colonization follow ed by Gl. mosseae.
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