The Effects of Different Concentrations of Crude Aqueous Extract of Artemisia annua on Soil Microbes

Artemisia annua (L) is known to inhibit the growth of seedlings leading us to hypothesize that it may also adversely affect soil microbial community. The effect of crude, aqueous leaf extracts of A. annua on soil microorganisms was therefore studied at (w/v) 0 (control), 1.0, 2.5, 5.0 and 7.5 percent (%) concentrations. The frequency of occurrence of bacterial isolates across treatments varied in the order Agromyces spp < Klebsiella spp < Micrococcus spp < Bacillus spp < Athrobacter spp < Pseudomonas spp. After 12 weeks of treatment application, the bacterial mean counts (cfu/g) were 173 x 10⁵ for the control, 57.5 x 10⁵ for the 1.0 %, 52.16 x 10⁵ for the 2.5 %, 47.8 x 10⁵ for the 5 %, and 44.3 x 10⁵ for the 7.50 % crude extract concentrations; the fungal mean counts were 6.78 x 10⁴, 30.5 x 10⁴, 34.3 x 10⁴, 35 x 10⁴ and 39.5 x 10⁴ cfu/g respectively. The fungal population varied in the order Aspergillus spp > Penicillium spp > Rhizopus spp > Corynespora Spp > Mucor spp > Microsporum spp > Fusarium spp. Thus, the extracts of Artemisia annua significantly reduced the bacterial population but increased the fungal population.