Iron is an essential micronutrient for the growth and development of both plants and humans, as it plays vital roles in processes such as protein synthesis, respiration and DNA replication. Leafy greens, vital dietary sources of iron, can be cultivated with increased bioavailable iron through hydroponics by customizing nutrient solutions. Conventionally, iron chelates like EDTA and DTPA, are used in hydroponics, but challenges persist in iron acquisition due to their pH dependency as well as quick oxidation to ferric ion which is harder to uptake by plants. Good sources of chelates that respond well to high pH values, like EDDHA, are often more expensive. Studies suggest that iron complexed with humic substances exhibits higher efficiency, though confirmation in large-scale hydroponic systems is still needed. Fulvic acids are water-soluble humic substances with lower molecular weights that hold promise as alternatives or supplements to synthetic chelates, enhancing iron uptake and stress tolerance. Hydroponic systems, such as Deep-Water Culture (DWC) or Nutrient Film Technique (NFT), impact plant growth and nutrient uptake differently based on temperature, EC, and pH. This research compared the effects of various iron chelators on lettuce and kale cultivation in DWC and NFT systems. Results indicate significant yield loss in iron-deficient kale, while iron-chelated solutions enhanced yields. The addition of fulvic acid to EDTA-chelated solutions notably improved kale yield in DWC compared to no iron and EDTA-only solutions. Leafy greens showed higher chlorophyll fluorescence (Fv/Fm ratio) and chlorophyll content in DWC compared to NFT. The results showed species-specific and system-specific responses. Notably, iron-chelated plants exhibit higher iron content correlating with increased shoot weight and chlorophyll content. The effect of fulvic acids and synthetic chelates might be synergistic, with both providing different advantages that can be complementary in hydroponic solutions. This study highlights the importance of iron management in hydroponics and the way forward for iron fortification techniques.
