Influence of complex stability on iron accumulation and redistribution for foliar- applied iron-organic acid complexes in maize

ABSTRACT

The relation between chemical attributes of complexed Fe sources and the efficiency of foliar fertilization is still unclear. This study aimed to investigate the influence of Fe-complex stability on iron accumulation and redistribution in maize by foliar application. The iron complexing agents used were biodegradable citric acid (CA), malic acid (MA), tartaric acid (TA), and oxalic acid (OA). The prepared FeSO₄ based complexes in the foliar spray solutions had ‘Fe: organic acid’ stoichiometric ratios of 1:1 and 1:2. Additionally, Fe-EDTA and FeSO₄ were also tested. The iron complexed fraction and the main complexed chemical species in the foliar spray solutions were determined using the Minteq software. Molecular modeling helped obtain probable complex structures and stabilities. The parameters, such as dry maize matter, shoot N accumulation, SPAD index, Fe-shoot, and Fe-root accumulation were determined. The complexes with TA and CA prepared at the stoichiometric ratio 1:2 showed the most favorable results in plant growth, iron nutrition. The stability and solubility of complexes affected iron accumulation and plant growth. The results indicate that iron redistribution to the roots increased in tandem with complex stability. Additionally, shoot iron accumulation was more significant for complexes with high solubility and low stability.

KEYWORDS:

• Carboxylic acids
• foliar fertilization
• iron deficiency
• iron complexes
• Gibbs free energy

Acknowledgments

Sara Dantas Rosa for cooperation in the experiment conduction, CNPq (307447-2019-7), and CAPES PROEX/AUXPE 593/2018 for financial support and scholarship provided for the first author. Many thanks to Dr. Maria Ligia de Souza Silva for allowing the use of hydroponics facilities in greenhouse conditions

Disclosure statement

The authors present no conflict of interest.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior; Fundação de Amparo à Pesquisa de Minas Gerais.