Effect of Poultry Manure Compost and Arbuscular Mycorrhizal Fungi on Cu Immobilization and Soil Microbial Communities in a Cu-Contaminated Soil Using the Metallophyte Oenothera Picensis

Soil metal contamination has emerged as a global environmental issue due to toxicity to living organisms. Traditional remediation techniques applied to metal-contaminated soils are intrusive and expensive, by which more environmental-friendly methods, such as phytoremediation, are necessary to remediate metal-contaminated soils. This study aimed to evaluate the combined effect of poultry manure compost (PMC) and indigenous arbuscular mycorrhizal (IM) fungi inoculation over copper (Cu) immobilization and the effectiveness of these elements promoting the plant growth and the soil microbial communities in a Cu-contaminated soil. A sandy Cu-contaminated soil (338 mg kg−1 of extractable Cu) was amended with PMC (2 and 4% w/w) in a pot experiment using the metallophyte Oenothera picensis. The plants were inoculated with the IM fungi isolated from the Cu-contaminated soils and grown for 3 months. PMC produced a liming effect, reduced the exchangeable Cu, and increased the amount of Cu-bound to organic and residual fractions. In addition, PMC also increased the biomass of O. picensis, which grew 8.5 times than the ones in unamended soil. Moreover, PMC incorporation stimulated soil microorganisms, increasing basal respiration and dehydrogenase activity modifying also the microbial community composition probably by reducing Cu availability and increasing carbon and nutrient sources to microorganism. On the contrary, the IM fungi inoculation reduced the plant biomass and increased the Cu translocation to the aboveground tissues. Therefore, the PMC is an effective amendment for remediating Cu-contaminated soils since it buffered soil pH, decreased Cu availability, supported the growth of O. picensis, and promoted mainly microbial activities in special shifting bacterial communities.