Effect of Application of Biostimulants on the Biomass, Nitrate, Pigments, and Antioxidants Content in Radish and Turnip Microgreens

Microgreens are a functional food that is very appreciated for their good taste and product features. They are produced all year without fertilizers and pesticides. In this paper, the effects of the application of commercial and natural biostimulants on the yield and nutraceutical properties of turnip greens and radish microgreens were investigated. The experiment consisted of four treatments based on biostimulants (Bio-1: TRAINER^®; Bio-2: AQUAMIN^®; Bio-3: leaf moringa extract; C: distilled water (control)) applied in two species (turnip greens and radish). Fresh and dry biomass, nitrate content, pigments, antioxidants, and antioxidant activity were measured. All biostimulants promoted biomass (both fresh and dry) accumulation in the radish but not in turnip greens. The treatment with biostimulant did not affect plant growth in the radish, while a depressive effect of Bio-1 upon plant growth was observed in turnip greens (−19% smaller than control). In radish, Bio-3 led to microgreens with the highest chlorophyll <i>a</i> content (+75% with respect to the control). Bio treatments did not affect the Chl (<i>a</i>, <i>b</i>, total) content in turnip greens. Biostimulants significantly lowered the nitrate content compared to the control (−27% nitrates) and significantly promoted TPC (+19% over the control) in the radish. They also stimulated antioxidant activity (DPPH), with the highest value in Bio-1, in the turnip, and in Bio-2 and Bio-3, in the radish. Conclusively, biostimulant treatments showed a positive effect on microgreens and, in particular, on those of the radish, improving various nutraceutical parameters.