Eco-Friendly Iron-Humic Nanofertilizers Synthesis for the Prevention of Iron Chlorosis in Soybean (Glycine max) Grown in Calcareous Soil. Cieschi M.T., Polyakov A.Y., Lebedev V.A., Volkov D.S., Pankratov D.A., Veligzhanin A.A., Perminova I.V., Lucena J.J. //Frontiers in Plant Science. 2019. V.10. P.413.
Iron deficiency is a frequent problem for many crops, particularly in calcareous soils and iron humates are commonly applied in the Mediterranean basin in spite of their lesser efficiency than iron synthetic chelates. Development and application of new fertilizers using nanotechnology are one of the potentially effective options of enhancing the iron humates, according to the sustainable agriculture. Particle size, pH, and kinetics constrain the iron humate efficiency. Thus, it is relevant to understand the iron humate mechanism in the plant-soil system linking their particle size, characterization and iron distribution in plant and soil using 57Fe as a tracer tool. Three hybrid nanomaterials (F, S, and M) were synthesized as iron-humic nanofertilizers (57Fe-NFs) from leonardite potassium humate and 57Fe used in the form of 57Fe(NO3)3 or 57Fe2(SO4)3. They were characterized using Mossbauer spectroscopy, X-ray diffraction (XRD), extended X-ray absorption fine structure spectroscopy (EXAFS), transmission electron microscopy (TEM) and tested for iron availability in a calcareous soil pot experiment carried out under growth chamber conditions. Three doses (35, 75, and 150 mu mol pot-1) of each iron-humic material were applied to soybean iron deficient plants and their iron nutrition contributions were compared to 57FeEDDHA and leonardite potassium humate as control treatments. Ferrihydrite was detected as the main structure of all three 57Fe-NFs and the plants tested with iron-humic compounds exhibited continuous long-term statistically reproducible iron uptake and showed high shoot fresh weight. Moreover, the 57Fe from the humic nanofertilizers remained available in soil and was detected in soybean pods. The Fe-NFs offers a natural, low cost and environmental option to the traditional iron fertilization in calcareous soils.
Foliar Application of Humic-Stabilized Nanoferrihydrite Resulted in an Increase in the Content of Iron in Wheat Leaves. Zimbovskaya M.M., Polyakov A.Y., Volkov D.S., Kulikova N.A., Lebedev V.A., Pankratov D.A., Konstantinov A.I., Parfenova A.M., Zhilkibaev O.T., Perminova I.V. //Agronomy. 2020. V.10. №12. P.1891.
The objective of this study was to synthesize iron (hydr)oxide nanoparticles (IONPs) stabilized by humic substances, and to estimate the feasibility of their use for foliar application on iron deficient plants. The IONPs were synthesized by rapid hydrolysis of iron(III) nitrate in a solution of potassium humate. The iron speciation and nanoparticle morphologies were characterized using X-ray diffraction, transmission electron microscopy, and Mossbauer spectroscopy. The obtained sample of IONPs was applied at concentrations of 1- and 10-mM Fe, and 0.2% urea was used as an adjuvant. Wheat plants (Triticum aestivum L. cv. L15) were used for the iron uptake test. For both of the concentrations tested, spraying the nanoparticles resulted in a 70–75% higher iron content in wheat leaves compared to ferric ammonium salt of ethylenediaminetetraacetic acid (Fe-EDTA). The synergistic effect of humic substances acting as a surfactant seemed to promote an increase in the iron uptake of the ferrihydrite nanoparticles compared to the aqueous Fe-EDTA solution used in this study. We concluded that humic-stabilized IONPs are much better suited to foliar application as compared to soil amendment when applied as a source of iron for plants. This is because humic substances act as a capping agent for nanoparticles and the surfactants enhance iron penetration into the leaf.