Evaluating the photodegradation of iron chelates: BHH/Fe3+ as an alternative to persistent iron fertilizers

Aminopolycarboxylic acids (APCAs) are widely used as chelating agents in agriculture to address iron (Fe) deficiency. However, the environmental concern of the most common APCAs, such as EDTA, has prompted the search for more sustainable alternative molecules. In this sense, the benzeneacetic acid 2-hydroxy-α-[(2-hydroxyethyl)amino] (BHH) has been presented as a novel chelating agent for Fe fertilization. This study investigates the photodegradation behavior of BBH Fe chelate, and compares it to the traditional Fe chelates (EDTA, HBED, and o , o EDDHA). Photodegradation experiments were conducted under various conditions, such as chelate concentration, pH, and light source, which can vary depending on the growing conditions where these fertilizers are used. The results showed that BHH/Fe 3+ exhibited an intermediate behavior between traditional phenolic and non-phenolic Fe chelates, undergoing degradation under light and dark conditions. The novel chelate BHH/Fe 3+ was more susceptible to light than its phenolic analogues. However, it maintained at least one-half of the initial Fe concentration under the most sensitive conditions (more extended time, low concentration, low pH, and high irradiation intensity). This stability was higher than that of the EDTA/Fe 3+ , indicating moderate stability under light exposure. In contrast, the traditional phenolic chelates remained the most stable under the tested conditions. Notably, the novel chelate BHH/Fe 3+ presented a great stability at pH 8, typical of calcareous soils where Fe chelates are required. This study highlights the importance of assessing the photodegradation performance of Fe chelates, which are typically exposed to light during their agronomical use. The factors under investigation, including chelate concentration, pH, and light type, exhibited a differential impact on the stability of Fe chelates. The chemical structure of Fe chelates was found to be a predominant factor in determining their stability. The high stability observed for the BHH/Fe 3+ at alkaline pH (less than 20–50% photodegraded in 7 days) suggests its potential as an alternative to traditional Fe chelates, especially EDTA/Fe 3+ . However, further research is still needed to determine its effectiveness in plants.