Potential of zinc-loaded graphene oxide and arbuscular mycorrhizal fungi to improve the growth and zinc nutrition of Hordeum vulgare and Medicago truncatula

Abstract

Zinc (Zn) is a limiting nutrient in soils for both plant yield and Zn nutrition. Soil Zn deficiency can be corrected by the application of Zn fertilisers. Novel formulations of Zn fertiliser are being developed using loaded graphene oxide (GO) sheets, but plant trials are limited. Barley (Hordeum vulgare) and Medicago (Medicago truncatula) plants were grown with and without inoculation with the arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis, in a substrate either unamended or amended with one of four different Zn fertilisers, including three Zn-GO formulations. The Zn-GO fertiliser was applied in granular, powder, and liquid forms, and the ZnSO4 applied as a solution; all fertilisers were added to 10 mg Zn kg−1 substrate. Plants were grown to maturity and measurements of biomass and Zn nutrition taken. A Zn-GO liquid fertiliser conferred greater biomass than the unamended control in both plant species, while a Zn-GO powdered fertiliser conferred greater Zn uptake in both species. Mycorrhizal Medicago plants had greater Zn uptake with Zn-GO powder than when mock-inoculated. Medicago was highly growth responsive to the AMF and this had a much larger effect than Zn fertiliser. Barley Zn nutrition was improved much more than yield by the addition of Zn fertiliser. The Zn-GO formulations show promise for delivery of Zn to two contrasting agriculturally important crops, with improvements in biomass accumulation and Zn nutrition achieved with at least one GO formulation in both crops.