Biofortification of kale microgreens with selenate-selenium using two delivery methods: Selenium-rich soilless medium and foliar application

Selenium (Se) is essential for human health as it is involved in various fundamental biological functions. This study aimed to assess the effects of Se enrichment in kale microgreens through biofortification in a soilless cultivation system. Two Se (as sodium selenate) application methods were assessed, including supplementation into the nutrient solution or as a foliar spray at four concentrations: 0, 10, 20 and 40 µM Se in a completely randomized design considering triplicates. For this purpose, minerals, nitrate and ammonium content, as well as fresh yield and dry matter of kale microgreens, were recorded after a 14-day growing period in an environmentally controlled vertical farm. Results showed that kale microgreens successfully accumulated up to 893.3 and 24 µg Se/ kg dry matter under the nutrient solution and foliar treatments, respectively, while yield remained unaffected. Selenium (Se) enrichment of the nutrient solution at 20 µM Se concentration resulted in the optimum treatment for fresh consumption purposes and supplying this element in human diets in the future, providing adequate dietary Se in less than five grams of the fresh kale microgreens.