# Iron Solubility and Uptake in Fava Bean and Maize as a Function of Iron Chelates under Alkaline Hydroponic Conditions

## TL;DR

This study compares how different iron chelates affect iron and phosphorus availability in fava bean and maize under alkaline conditions.

## Contribution

The study introduces Fe-HBED as a more effective iron chelate for maintaining solubility and nutrient uptake in alkaline soils.

## Key findings

- Fe-HBED outperformed Fe-EDTA and Fe-DTPA in maintaining Fe and P solubility under high alkalinity.
- Fava bean showed improved nutrient uptake and stress tolerance with chelated micronutrients.
- Speciation modeling revealed Fe displacement from Fe-EDTA at high pH, forming insoluble compounds.

## Abstract

Iron-EDTA becomes unstable above pH 6.5, resulting in
competition
among metal ions (Fe, Cu, Zn, and Mn) for EDTA and reduced Fe availability.
This study examined nutrient precipitation dynamics and interactions
between chelated and sulfate forms of Zn, Mn, and Cu with Fe-EDTA
in fava bean and maize under increasing alkalinity (0, 5, and 15 mM
NaHCO3). In fava bean, chelated micronutrients significantly
increased shoot Fe, P, and Zn concentrations and improved metabolic
activity and oxidative stress tolerance. Maize was more sensitive
to alkalinity but showed similar nutrient responses at 5 mM NaHCO3. Speciation modeling (MINEQL+5.0) indicated Fe displacement
from Fe-EDTA at high pH, forming insoluble FePO4 and Fe­(OH)3. Incubation studies demonstrated that Fe-HBED maintained
higher Fe, Ca, and P solubility than Fe-EDTA and Fe-DTPA under alkaline
conditions. SEM-EDX analysis linked stable Fe chelates to lower P
in precipitates. Results highlight Fe-HBED’s effectiveness
in ensuring Fe and P availability under alkalinity.