Effects of Glyphosate on Yield and Shelf Life of Yam: A Case Study in Wulensi in the Nanumba Traditional Area, Ghana

Abstract— This study was undertaken to elucidate the effect of glyphosate on the soil mycoflora of yam farms and yam rots as a follow up on a previous study which suggested that glyphosate use had no effect on yam rots as held by farmers. This study was set up at the field level and in the laboratory to investigate these concerns. Two yam varieties; “laribako” and “olodo” were grown in a replicated control trial design under the conditions of chemical weed control (use of glyphosate) and manual weed control in three replicate sites in the Wulensi traditional area of the Nanumba south district. The transient effect of glyphosate on fungal population and diversity were determined by serial dilution method on Cooke’s media. Combined methods of soil plate fungi isolation and food poison was used to determine the effect of normal and double the normal rate of glyphosate application on fungal population and diversity. Fungal species belonging to the genera Aspergillus, Fusarium, Mucor, Penicillium, Rhizopus, Rhodotorula and Trichoderma were isolated. The positive control (fungicide) totally inhibited fungal growth. Generally, there were no significant differences (P≤0.05) among the fungal population recorded for the glyphosate treated soils and the negative control (water). The glyphosate treated soil initially recorded a lower fungal population, which subsequently increased with passing days. The recorded fungal population ranged from 3.6×105 to 7.7×105 CFU/g for 10 days old glyphosate treated soil and non-treated soil respectively. The normal and double the normal rate of glyphosate application did not significantly (P≤0.05) affect the fungal population among the various treatments, but influenced fungal diversity over a short period of time. The study revealed after the storage period, that there was no difference (P > 0.05) in rots between yam treated with glyphosate herbicide and yam manually weeded. The study further revealed that glyphosate application at the recommended rate had no adverse effect on the mycoflora of the soil under consideration; hence did not distract the natural mycoflora of the soil which could have resulted in the proliferation of fungal pathogens causing yam rot.