Leonardite iron humate and synthetic iron chelate mixtures in Glycine max nutrition.

BACKGROUND: The aim of this work was to study the possible synergic effect between mixtures with iron leonardite humate (L/Fe3+ ) and synthetic chelates iron (Ch/Fe3+ : o,oEDDHA /Fe3+ or HBED/Fe3+ ), and to reevaluate the classical chelate shuttle-effect model. Different molar ratios of L/Fe3+ :Ch/Fe3+ , different doses, and different sampling times were used in hydroponic and soil experiments using soybean (Glycine max) as a model Strategy I crop in calcareous conditions. Ligand competition between the humate and chelating agents was also examined. RESULTS: Iron humate participates in the chelate shuttle mechanism, providing available Fe to the chelating agent and then to the plants, showing a slight synergic effect. After a few days, the contribution of the chelates to the Fe nutrition decreases substantially, but the contribution of the humates is maintained. CONCLUSIONS: The most efficient ratio was two parts of iron humates and one part of iron chelate. In particular, HBED/Fe3+ was the most suitable iron chelate because its lasting effect fits the iron humate long-term effect better. The soluble iron in soil increased and the shoot-to-root iron translocation improved due to a synergic effect by a shuttle effect exerted by iron chelate in the mixture. © 2021 Society of Chemical Industry.

Eco-Friendly Iron-Humic Nanofertilizers Synthesis for the Prevention of Iron Chlorosis in Soybean (Glycine max) Grown in Calcareous Soil.

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 Mössbauer 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 µmol 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.

Long-Term Effect of a Leonardite Iron Humate Improving Fe Nutrition As Revealed in Silico, in Vivo, and in Field Experiments.

Novel, cheap and ecofriendly fertilizers that solve the usual iron deficiency problem in calcareous soil are needed. The aim of this work is to study the long-term effect of an iron leonardite fertilizer on citrus nutrition taking into account a properly characterization, kinetic response with a ligand competition experiment, efficiency assessment using Saccharomyces cerevisiae strain and finally, in field conditions with citrus as test plants. Its efficiency was compared with the synthetic iron chelate FeEDDHA. Leonardite iron humate (LIH) is mainly humic acid with a high-condensed structure where iron is present as ferrihydrite and Fe3+ polynuclear compounds stabilized by organic matter. Iron and humic acids form aggregates that decrease the iron release from these kinds of fertilizers. Furthermore, LIH repressed almost 50% of the expression of FET3, FTR1, SIT1, and TIS11 genes in Saccharomyces cerevisiae cells, indicating increasing iron provided in cells and improved iron nutrition in citrus.

EDTA Shuttle Effect vs. Lignosulfonate Direct Effect Providing Zn to Navy Bean Plants (Phaseolus vulgaris L 'Negro Polo') in a Calcareous Soil.

Zn-Lignosulfonates (LS) fertilizers are used as an eco-friendly alternative to chelate formulations. The mechanisms of Zn release in the rhizosphere by both types of products are compared. The ability to provide Zn to Phaseolus vulgaris L of non-modified and chemically modified ZnLS and ZnEDTA is compared in a hydroponic assay. Stable isotope 67Zn was used to study Zn source (fertilizer, ZnFer, or native, ZnNat) uptake and distribution in plants in two soil pot experiments. ZnEDTA was the best treatment to provide both ZnFer and ZnNat to navy bean plants. A shuttle effect mechanism and an isotopic exchange may occur. ZnLS from eucalyptus (ZnLSE) provides more Zn to the plant than LS from spruce. Chemical modifications of ZnLSE does not improve its efficiency. A double dose of ZnLSE provides similar ZnFer in leaves and similar soluble ZnFer content in soil than ZnEDTA. A model for the Zn fertilizers behavior in the soil and plant system is presented, showing the shuttle effect for the synthetic chelate and the direct delivery in the rhizosphere for the ZnLS complex.