Commonly Used Engineered Nanomaterials Improve Soil Health via Suppressing Soil-Borne Fusarium and Positively Altering Soil Microbiome

The use of engineered nanomaterials (NMs) as novel antimicrobial agents has garnered significant attention in agriculture. The antimicrobial properties of 5 mg/kg metal oxide (copper oxide and zinc oxide nanoparticles, CuO and ZnO NPs)- and carbon (reduced graphene oxide and multiwalled carbon nanotubes, rGO and MWCNT)-based NMs on two soil-borne fungal pathogens, Fusarium oxysporum f.sp. lactucae (F.o.lact) and Fusarium oxysporum f.sp. lycopersici (F.o.lyco), were evaluated over a 21-day incubation period. Both metal- and carbon-based NMs reduced the dehydrogenase activity (DHA) in Fusarium-infested soil by more than 40% relative to the infested controls; the efficacy of antifungal efficacy was CuO NPs > ZnO NPs > rGO > MWCNT. Similar decreases in the soil activities of urease (UE), sucrase (SC), acid phosphatase (ACP), and polyphenol oxidase (PPO) suggest that NMs could effectively inhibit Fusarium growth in soil over time. The total available metal fractions, including acid extractable fraction, Fe/Mn oxidation state, and the fraction bound to organic matter, were increased by 5.99-7.29% with metal-based NM compared to the infested controls. The Shannon index of microbial communities in the infested soils with metal-based NMs was increased by 12.2-23.5% relative to infested controls. Similarly, carbon-based NMs increased the Shannon index of the fungal community by 10.18-29.86%. Importantly, the relative abundance of Fusarium was decreased with both metal- and carbon-based NMs. These NMs also increased the relative abundance of beneficial microorganisms in infested soil, such as Pseudomonas, which was increased by 29.7-96.2% with metal-based NMs relative to the untreated controls. These findings demonstrate that NMs at appropriate doses could inhibit the Fusarium abundance and subsequent crop damage while simultaneously fostering the development of beneficial microorganisms in soil.