Combining non-microbial biostimulants and different application methods affects yield, antioxidant activity,...

Microgreens are considered a good source of nutritional and functional compounds, offering humans significant health benefits. Biostimulants are recognized as a sustainable tool to elicit growth and development of vegetables. The aim of this research was to evaluate the effects of a plant protein hydrolysate (PH) and a seaweed extract (SWE) - supplied via seed priming or root application - on pea and arugula microgreens performance. Moreover, a partial budget analysis was conducted to assess the economic implication of biostimulants application. Hydropriming and PH-priming treatments enhanced pea microgreens yield compared to the root application treatment's counterpart by 53.2% and 33.3%, respectively. Nitrates were increased by SWE application and reduced by PH supply, in both species, compared with the not biostimulated plants, particularly when biostimulants were applied via root application [SWE, + 26.6% (pea); PH, -19.9% (pea), SWE, + 6.5% (arugula); PH, -24.3% (arugula)]. The combination of biostimulants and priming enhanced ascorbic acid compared to the control × root application (negative control) in pea microgreens by 20.9%, whereas, in arugula, either the biostimulants or priming alone significantly improved the aforesaid parameter. Biostimulants boosted total polyphenol content in pea microgreens, supplied via priming (SWE, + 21.5%; PH, 22.8%, compared to the hydropriming) or root application (SWE, + 15.7%; PH, 14.6%, compared with the negative control). Total polyphenols in arugula microgreens increased when PH and SWE were supplied via priming (+14.3%, for both biostimulants, compared to the hydropriming). Biostimulants significantly increased the antioxidant capacity (DPPH), although the method of application did not significantly affect DPPH. These findings confirmed the efficacy of biostimulants in modulating microgreens qualitative features. Furthermore, the partial budget analysis underlined that the use of both biostimulants, independently of the type of application, is economically suitable for pea, but not always convenient for arugula. The application of PH or SWE, especially via root application, was a suitable strategy to increase the nutritive and functional values of pea and arugula microgreens, contributing to their potential as valuable novel foods for human consumption.