Inhibitory Effects of Indigenous Aspergillus Niger Spore Suspension on Weed Emergence and Growth in Non-Sterile Maize Rhizosphere Soil

Weed management remains a major challenge in sustainable maize production, often relying on chemical herbicides with environmental drawbacks. This study evaluated the bioherbicidal potential of Aspergillus niger on dominant weed species in maize rhizosphere soil under non-sterile conditions. Indigenous A. niger was isolated, characterized, and cultured for inoculum preparation. A completely randomized pot experiment was conducted using maize-planted soils treated with A. niger spore suspensions (10⁴ spores/mL) at different application timings: pre-emergence, early post-emergence, and late post-emergence. Weed emergence, stem height, and leaf width were monitored weekly for six weeks. Soil microbial load and pH were also analyzed before treatment and at the experiment’s conclusion. Results showed that early post-emergence application of A. niger moderately suppressed weed emergence and stem elongation, with significant differences observed over time (p ≤ 0.001). However, no substantial effect was recorded on leaf width. Soil microbial counts decreased post-treatment, while pH levels slightly increased. Correlation analysis revealed a strong negative association between microbial load and weed performance parameters, suggesting a possible suppressive effect of A. niger on weed growth mediated by microbial shifts. Despite these observations, the suppressive effects were moderate and diminished over time, indicating that low inoculum load and single application may not provide sustainable weed control under field conditions. Further studies are recommended to explore higher inoculum doses, repeated applications, and interactions with environmental factors to optimize A. niger’s bioherbicidal efficacy.