Iron (Fe) and Zinc (Zn) are two micronutrients which are crucial for human health and proper functioning of the circulatory, endocrine, immune, nervous, and reproductive systems. Deficiencies in dietary Fe and Zn can result in numerous illnesses and disorders and are among the most prevalent micronutrient deficiencies worldwide. There is an urgent need for improving the dietary intake of these micronutrients and a promising, quick, and effective improvement strategy is agronomic biofortification. Microgreens are an ideal and versatile choice for meeting nutritional needs. They are nutrient-dense, have low phytic acid content, can be produced for a range of species, and have a relatively short growth cycle – making them a convenient biofortification target crop. Previous studies’ attempts towards the simultaneous biofortification of Fe and Zn have indicated their antagonistic interactions during uptake, where the increase of one mineral led to a decreased uptake of the other. However, limited information is available about the opportunity of enriching microgreens with both nutrients using fertigation. Therefore, in this study we aimed to assess the optimal combination of Fe and Zn fertilizer concentrations, provided via fertigation, to maximize their simultaneous accumulation in radish and sunflower microgreens without impairing yield and quality. Using a completely randomized block design setup, a factorial combination of FeSO4 (0, 20, and 40 mg/L of Fe) and ZnSO4 (0, 10, and 20 mg/L of Zn) was tested. Across both species, it was observed that fertigation using the treatment combination of 40 mg/L FeSO4 and 20 mg/L ZnSO4, (Fe40-Zn20), resulted in a substantial increase of both micronutrient levels. Compared to the untreated control, the Fe40-Zn20 treatment increased Fe and Zn accumulation by about 200% and 900%, respectively, in radish microgreens, and about 180% and 600% in sunflower microgreens. Additionally, this treatment resulted in minimal yield reduction. Fresh and dry biomass decreased by approximately 23% and 9%, respectively, in radish microgreens, and 38% and less than 1% in sunflower microgreens. Although increasing both Fe and Zn content proves to be a challenging endeavor, this study revealed evidence of an optimal combination of selected Fe and Zn sources and application rates that, via fertigation, was effective in their simultaneous enrichment in two microgreen species.
