Impact of Zinc Oxide Nanoparticles Amended Organic Manure on Arachis hypogaea Growth Response and Rhizosphere Bacterial Community

Abstract

The effect of zinc oxide nanoparticle-organic manure amended ultisol and loam soils on plant growth response and rhizosphere bacterial community of peanut (Arachis hypogaea) was evaluated using standard methods under greenhouse conditions. Results indicate germination rates ranged between 30 and 100% in the amended soils compared to 50 and 70% in the controls. ZnO nanoparticles exerted concentration-dependent and varying effects on the plant root and shoot lengths, weights, nodules and pod formation in the two soil types. Heterotrophic bacterial counts ranged from 7.21 ± 0.51 to 7.38 ± 0.5 Log10CFUg-1 in the amended ultisol and 6.99 ± 0.55 Log10CFUg-1 in the control with a log reduction to 6.70 ± 0.39 Log10CFUg-1 in 500 mgkg⁻¹ ZnO spiked soil. Counts in the amended loam soil ranged between 6.59 ± 0.48 and 7.22 ± 0.41 Log10CFUg-1 relative to 6.80 ± 0.58 Log10CFUg-1 in the control. ZnO induced concentration-dependent effect on oxygen uptake rate relative to the controls. The organisms were members of the genera Lactobacillus, Pseudomonas, Bacillus, Rhizobium, Xanthobacter, Enterobacter, Citrobacter, Nitrosomonas and Agromyces. ZnO nanoparticle exerted concentration-dependent stimulatory and inhibitory effects on the plant growth response, oxygen uptake rate and induced temporal shifts in soil microbial abundance. It is challenging to generalize a consistent response of the plant or microorganisms because ZnO nanoparticles interacted with A. hypogaea and soil bacterial community in ways that differ in the ultisol and loam soil.

Influence of Zinc Oxide Nanoparticles on Soil Physicochemical Properties and Arachis hypogea Rhizosphere Microbial Community

“…The ultisol and loam soils were excavated from the University of Uyo Farm, Nwaniba Road, Uyo and transported to the greenhouse in the Department of Botany and Ecological Studies, University of Uyo, Uyo, Nigeria. The soils were amended with organic manure and spiked with zinc oxide nanoparticles as previously reported [16]. Briefly, 14 kg of soil and 6 kg of organic manure (poultry dropping) were placed into seven wooden troughs (30 cm x 30 cm) lined with polyethene in duplicate.…”

“…High copper content in soils exacerbates the toxic effect of xenobiotics evidenced in delayed germination and reduced shoot vigor [30]. The germination and growth response of A. hypogaea in the ultisol and loam soils were negatively impacted [16] and accumulation of copper ions, in part, probably contributed to the poor plant performance.…”

“…The differences between the THB counts in the amended and control soils was significant at p = 0.05. Indeed, the decomposition of organic matter had effect on bacterial composition [34] and correlated with the differences in the composition of A. hypogaea rhizosphere bacterial biomass and abundance in the amended and the controls ultisol and loam soil [16]. Further to this, nanoparticles are implicated in enhanced plant growth in environments with high salt concentration [23] which plausibly accounted for some of the positive impacts on the bacterial and A. hypogaea growth response [16] in the ultisol and loam soil despite the salt stress.…”