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Nanoscale zero-valent iron (nZVI) might generate positive and negative effects on plant growth, since it acts as either hazardous or growth-promotion role. It is still unclear whether such dual roles can be mediated by arbuscular mycorrhizal fungi (AMF) in plant-AMF symbiosis. We first identified that in 1.5 g kg−1 nZVI (≤1.5 g kg−1 positively), maize biomass was increased by 15.83%; yet in 2.0 g kg−1 nZVI, it turned to be declined by 6.83%, relative to non-nZVI condition (CK, p < 0.05), showing a negative effect. Interestingly, the inoculation of AMF massively improved biomass by 45.18% in 1.5 g kg−1 nZVI, and relieved the growth inhibition by 2.0 g kg−1 nZVI. The event of water use efficiency followed similar trend as that of biomass. We found that proper concentration of nZVI can positively interact with rhizosphere AMF carrier, enabling more plant photosynthetic carbon to be remobilized to mycorrhiza. The scanning of transmission electron microscopy showed that excessive nZVI can infiltrate into root cortical cells and disrupt cellular homeostasis mechanism, significantly increasing iron content in roots by 76.01% (p < 0.05). Simultaneously, the images of scanning electron microscopy showed that nZVI were attached on root surface to form an insoluble iron ion (Fe3+) layer, hindering water absorption. However, they were efficiently immobilized and in situ intercepted by extraradical hyphae in mycorrhizal-nZVI symbiosis, lowering iron translocation efficiency by 6.07% (p < 0.05). Herein, the optimized structure remarkably diminished aperture blockage at root surface and improved root activities by 30.06% (p < 0.05). Particularly, next-generation sequencing demonstrated that appropriate amount of nZVI promoted the colonization and development of Funneliformis mosseae as dominant species in rhizosphere, confirming the positive interaction between AMF and nZVI, and its regulatory mechanism. Therefore, dual effects of nZVI can be actively mediated by AMF via rhizosphere interactions. The findings provided new insights into the safe and efficient application of nanomaterials in agriculture. [Display omitted] [ABSTRACT FROM AUTHOR]

We investigated a nature-based solution (NbS) via incorporating biocrust into alfalfa-maize intercropping system to test carbon sequestration in seriously eroded agricultural soils. Field investigation showed that the NbS (moss-dominated biocrust + intercropping) massively lowered surface soil erosion by 94.5% and soil carbon (C) and nitrogen (N) loss by 94.7 and 96.8% respectively, while promoting rainwater interception by 82.2% relative to bare land (CK). There generally existed positive interactions between biocrust and cropping in the integrated standing biodiversity system. Enhanced plant biomass input into soils substantially promoted soil fungal community diversity and abundance under NbS (p < 0.05). This enabled NbS to evidently improve soil macroaggregate proportion and mean weight diameter. Critically, topsoil carbon storage was increased by 2.5 and 10.7%, compared with CK and pure intercropping (p < 0.05). Conclusively, the standing diversity under such NbS fostered soil C sequestration via water interception and plant-soil-microbe interactions in degraded agricultural soils., Competing Interests: The authors declare that they have no conflict of interest., (© 2022 The Author(s).)