Increased plant growth with hematite nanoparticle fertilizer drop and determining nanoparticle uptake in plants using multimodal approach

There is an emerging scientific interest in the use of nanoparticle fertilizers for enhanced agricultural and bioenergy crop production to meet the growing food and energy demands of the world. The objective of designing the nanoparticle fertilizers is to effectively deliver the required nutrients for the plants without adding large quantities of fertilizer to the environment. However, most reports on nanoparticle fertilizers so far, involved the addition of nanoparticles to the hydroponic system or the soil. In this study, we report a new modified seed presoak strategy using a drop of Fe-enriching hematite nanoparticle dispersion to enhance plant growth and production in four different legume species, i.e., chickpea, green gram, black bean, and red bean. The hematite nanoparticle fertilizer drop promoted a 230-830% increase in plant growth with green gram showing the highest increase, based on our prolonged and statistically reliable growth studies. In general, we observed an increase in the survival span of plants, a twofold increase in fruit production per plant, nearly two times faster fruit production, and healthy second-generation plants with the nanoparticle treatment; however, there were slight species-specific variations. We used a novel multimodal material characterization approach combining three techniques, hyperspectral imaging, Fourier transform infrared spectroscopy (FTIR), and inductively coupled plasma optical emission spectroscopy (ICP-OES), to evaluate the internalization and transport of the nanoparticle fertilizer within the plants. Our results indicated that the hematite nanoparticles were transported through the roots and stems and were localized in the leaves after 10 days of growth in pots of soil. Therefore, the modified seed presoaking method using a drop of hematite nanoparticle will be highly attractive in enhancing plant growth and health, while minimizing environmental impacts.