Zinc biofortification via fertigation using alternative zinc sources and concentration levels in pea, radish, and sunflower microgreens

Zinc (Zn) is a key micronutrient essential for human health, and its deficiency affects over 17 % of the global population. The consumption of Zn-biofortified foods is one strategy for addressing this malnutrition issue. Supplying Zn-enriched nutrient solutions via fertigation is a prominent method for enhancing the content of Zn in vegetable crops. Among vegetables, microgreens are considered a particularly suitable biofortification target crop due to their high nutrient density, swift growth rate, and low phytic acid content. However, there is limited knowledge on the optimal Zn sources and application rate for the biofortification of different microgreen species via fertigation. Therefore, this study aimed to examine the effects of alternative Zn sources (ZnSO4, ZnO, and Zn-EDTA) and application rates (0, 5, 10, and 15 mg/L of Zn) on yield components, mineral content, and phytochemical profile of pea, radish, and sunflower microgreens grown in a soilless cultivation system. Zn fertigation increased Zn content and the nutritional profile (flavonoids, total phenols, antioxidant activity, and ascorbic acid) of all three microgreen species. Microgreens fertigated with 15 mg/L ZnSO4 solution, increased Zn content nearly by a factor of 5, 13, and 6 in pea, radish, and sunflower, relative to their control not supplied with Zn (61.01, 50.26, and 65.87 mg/g DW), respectively. ZnSO4 was the most effective source of Zn, followed by ZnO and Zn-EDTA. Zn accumulation resulted in minimal or no fresh yield reduction. However, the concentration of other essential microminerals, like Fe, decreased with Zn accumulation in all three species. In conclusion, Zn biofortification via fertigation is effective in enriching microgreens with Zn, while also enhancing their nutritional profile. Nevertheless, selecting the proper Zn source and application rate is critical to achieving the target Zn concentration without reducing yield and/or the content of Fe and other minerals.