ASHS 2025 Conference

Iron (Fe) deficiency is one of the leading micronutrient deficiencies in the world, impacting almost two billion people globally. Contributing factors include non-diverse diets (cereal grain-centered diets, processed and junk foods) that are characterized by relatively low bioavailable Fe levels. Additionally, 30% of cultivated soils around the world report low Fe availability. Inadequate levels of dietary Fe can cause numerous physiological disorders and impaired cognitive functioning, with pregnant women and infants being particularly vulnerable. To help alleviate the harm of Fe malnutrition, a straightforward and sustainable solution to increase dietary Fe availability is through agronomic biofortification of crops. Unfortunately, Fe uptake by plants is problematic, especially in alkaline and oxidizing conditions. However, various studies have reported the role of ascorbic acid (AA) as an enhancer of Fe absorption. A suitable candidate crop for Fe biofortification are microgreens, as they are nutritional powerhouses that have low phytic acid levels, short growth cycles, and are typically consumed raw. Testing the use of AA for Fe biofortification in microgreens has received limited attention in literature. Therefore, in this study we investigate in a soilless system the effect of different Fe sources with and without organic acids (Ferric sulfate, Ferric sulfate 0.1% Ascorbic acid, Ferric citrate), applied via fertigation at different concentrations (0, 15, 30, 45 mg/L of Fe), on Fe content of sunflower microgreens. Treatments were arranged in a completely randomized factorial design using three replications. We discovered that Ferric sulfate 0.1% AA provided at 45 mg/L was the most effective source and rate in increasing Fe content, resulting in approximately 300% increase compared to the untreated control. Fertigating with Ferric sulfate 0.1% AA also showed a significant increase in total antioxidants and total phenol concentrations, but a decrease in chlorophyll and carotenoid levels. When using sodium hydroxide (NaOH) to adjust the nutrient solution pH, the same treatment was associated with relatively high Na content and resulted in an average reduction in fresh and dry biomass of 50% and 30%, respectively. Further assessment of Fe sources, concentrations, and bases for pH adjustment should be considered to not compromise yield and nutritional quality. However, these results indicate that through fertigation, the supplementation of AA with Fe fertilizers can significantly promote the enrichment of Fe as well as certain phytochemicals in sunflower microgreens. This strategy can produce Fe-biofortified functional foods that can potentially improve health outcomes of Fe-deficient individuals.