Foliar Application with Iron Oxide Nanomaterials Stimulate Nitrogen Fixation, Yield, and Nutritional Quality of Soybean

Abstract

Sustainable strategies for the management of iron deficiency in agriculture are warranted because of the low use efficiency of commercial iron fertilizer, which confounds global food security and induces negative environmental consequences. The impact of foliar application of differently sized γ-Fe2O3 nanomaterials (NMs, 4–15, 8–30, and 40–215 nm) on the growth and physiology of soybean seedlings was investigated at different concentrations (10–100 mg/L). Importantly, the beneficial effects on soybean were size- and concentration-dependent. Foliar application with the smallest size γ-Fe2O3 NMs (S-Fe2O3 NMs, 4–15 nm, 30 mg/L) yielded the greatest growth promotion, significantly increasing the shoot and nodule biomass by 55.4 and 99.0%, respectively, which is 2.0- and 2.6-fold greater than the commercially available iron fertilizer (EDTA-Fe) with equivalent molar Fe. In addition, S-Fe2O3 NMs significantly enhanced soybean nitrogen fixation by 13.2% beyond that of EDTA-Fe. Mechanistically, transcriptomic and metabolomic analyses revealed that (1) S-Fe2O3 NMs increased carbon assimilation in nodules to supply more energy for nitrogen fixation; (2) S-Fe2O3 NMs activated the antioxidative system in nodules, with subsequent elimination of excess reactive oxygen species; (3) S-Fe2O3 NMs up-regulated the synthesis of cytokinin and down-regulated ethylene and jasmonic acid content in nodules, promoting nodule development and delaying nodule senescence. S-Fe2O3 NMs also improved 13.7% of the soybean yield and promoted the nutritional quality (e.g., free amino acid content) of the seeds as compared with EDTA-Fe with an equivalent Fe dose. Our findings demonstrate the significant potential of γ-Fe2O3 NMs as a high-efficiency and sustainable crop fertilizer strategy.

Progress toward Room-Temperature Synthesis and Functionalization of Iron-Oxide Nanoparticles

“…Moreover, Moringa oleifera treatment with Fe 3 O 4 NPs improved its growth by reducing the salinity effects [ 6 ]. On the other hand, experiments with soybeans demonstrated the outstanding potential of γ-Fe 2 O 3 NPs as sustainable and highly efficient crop fertilizers, especially NPs with the smallest sizes [ 7 ]. In water remediation, several bare and functionalized γ-Fe 2 O 3 and Fe 3 O 4 NPs exhibit remarkable removal efficiencies of toxic metal ionic species and different dye types [ 2 , 8 ].…”

“…There are several works reported in the literature that deal with the synthesis parameters and their optimizations to produce iron-oxide nanoparticles for different applications [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. In particular, a current review [ 2 ] summarizes the principal issues of these nanomaterials, where features such as scalability, production, and application costs are discussed because they are some of the main challenges for their industrial-level implementation.…”

Biosynthesized metal oxide nanoparticles for sustainable agriculture: next-generation nanotechnology for crop production, protection and management

“…Furthermore, S-Fe 2 O 3 NMs boosted carbon absorption in nodules, supplying greater energy for nitrogen fixation, according to transcriptome and metabolomic investigations. 109 Likewise, it was observed that treatment to Fe 3 O 4 NPs boosted symbiotic nitrogen fixation and increased total nitrogen content in the shoot (26.5–50.2%) and root (24.1–48.2%) of exposed common bean plants as compared to controls. 110…”

Carbon Dots Improve Nitrogen Bioavailability to Promote the Growth and Nutritional Quality of Soybeans under Drought Stress

“…The moisture content in soybean tissues was calculated from the ratio of dry to fresh weight. The carbohydrate content was determined as previously reported . Morphological parameters of roots were analyzed by a root scanner (Instruments Regent LA2400, Japan).…”

“…The carbohydrate content was determined as previously reported. 66 Morphological parameters of roots were analyzed by a root scanner (Instruments Regent LA2400, Japan). The detailed collection method of root exudates is described in text S4 in the Supporting Information.…”