Application of dry olive residue-based biochar in combination with arbuscular mycorrhizal fungi enhances the microbial status of metal contaminated soils

Abstract

Biochar made-up of dry olive residue (DOR), a biomass resulting from the olive oil extraction industry, has been proposed to be used as a reclamation agent for the recovery of metal contaminated soils. The aim of the present study was to investigate whether the soil application of DOR-based biochar alone or in combination with arbuscular mycorrhizal fungi (AMF) leads to an enhancement in the functionality and abundance of microbial communities inhabiting metal contaminated soils. To study that, a greenhouse microcosm experiment was carried out, where the effect of the factors (i) soil application of DOR-based biochar, (ii) biochar pyrolysis temperature (considering the variants 350 and 500 °C), (iii) soil application dose of biochar (2 and 5%), (iv) soil contamination level (slightly, moderately and highly polluted), (v) soil treatment time (30, 60 and 90 days) and (vi) soil inoculation with Funneliformis mosseae (AM fungus) on β-glucosidase and dehydrogenase activities, FA (fatty acid)-based abundance of soil microbial communities, soil glomalin content and AMF root colonization rates of the wheat plants growing in each microcosm were evaluated. Biochar soil amendment did not stimulate enzyme activities but increased microbial abundances. Dehydrogenase activity and microbial abundances were found to be higher in less contaminated soils and at shorter treatment times. Biochar pyrolysis temperature and application dose differently affected enzyme activities, but while the first factor did not have a significant effect on glucosidase and dehydrogenase, a higher biochar dose resulted in boosted microbial abundances. Soil inoculation with F. mosseae favored the proliferation of soil AMF community and increased soil glomalin content as well as rates of AMF root colonization. This factor also interacted with many of the others evaluated to significantly affect soil enzyme activities, microbial abundances and AMF community. Our results indicate that the application of DOR-based biochar along with AMF fungi is an appropriate approach to improve the status of microbial communities in soils with a moderate metal contamination at short-term.

Interactive Suitability of Rice Stubble Biochar and Arbuscular Mycorrhizal Fungi for Improving Wastewater-Polluted Soil Health and Reducing Heavy Metals in Peas

“…Therefore, they play important functions in soil fertility and availability of nutrients to plants. However, variations in soil quality, especially the presence of HMs, negatively affect microbial activities and enzymes secreted by microbes [16]. Formerly, the application of BR in HM-polluted soils was reported to increase the activities of soil enzymes [29].…”

“…Unfortunately, WW contains toxic heavy metals (HMs), such as Pb, Cd, Zn, Ni, Hg, and As. Soil irrigated with WW (SIW) results in HM accumulation in the food chain, causing several human health Sustainability 2024, 16, 634 2 of 18 issues [6,7]. Irrigating soil with WW negatively influences its structure, water-holding capacity (WHC), infiltration rate, and hydraulic conductivity [8].…”

“…Moreover, improvements in the physicochemical properties of soil and plant growth in SIW with COM application have also been reported [7]. Interestingly, biochar (BR), a carbon-based material, can have agronomic benefits (soil fertility and plant growth) and remediate HM-polluted soil [16,17]. The production method and mineral composition of feedstock define the features of BR.…”