Nanoscale Iron (Fe₃O₄) Surface Charge Controls Fusarium Suppression and Nutrient Accumulation in Tomato (<i>Solanum lycopersicum</i> L.)

With the growing recognition that conventional agriculture will not be able to meet food production demands, innovative strategies to reach food security are imperative. Although nanoscale fertilizers are attracting increased attention as a sustainable platform for agricultural applications, limited data exist on how surface charge influences overall efficacy relative to disease suppression and nutrient accumulation. This study investigated the effect of positively and negatively charged iron oxide nanoparticles (Fe3O4 NPs) on the growth of tomato (Solanum lycopersicum L.) plants and their disease resistance against the pathogen Fusarium oxysporum f. sp. lycopersici at both the greenhouse and field scale. In addition, a theoretical model of the biointerface was employed for a mechanistic understanding of the interaction and attachment efficiency between NPs and tomato leaves after foliar exposure. In the greenhouse, both positively and negatively charged Fe3O4 NPs significantly suppressed Fusarium wilt by 41.4 and 44.6% and increased plant shoot biomass by 327.6 and 455.0%, respectively, compared to the diseased control. The impact of the NP surface charge was apparent; positively charged Fe3O4 NPs demonstrated superior efficacy compared to their negatively charged counterparts in mitigating disease damage and regulating nutrient (Na, Si, and Cu) accumulation. Computationally, positively charged Fe3O4 NPs consistently migrate toward lipid layers, indicative of a pronounced affinity between these entities compared with the negatively charged particles, which aligns with the experimental data. The findings highlight the importance and tunability of nanomaterials properties, especially the surface charge, in optimizing the use for disease suppression and nutrient modulation, which offers a great potential for sustainable agriculture.