Microalgae-based biostimulants may help reduce inputs in protected ornamental production, yet evidence across multiple growing seasons remains limited. We conducted a three-year polytunnel trial with six Pelargonium cultivars and applied two strains from the Mosonmagyaróvár Algal Culture Collection (MACC-612, Nostoc piscinale; MACC-922, Chlorella vulgaris). Using a factorial general linear model, we detected significant treatment effects on total dry mass, root mass, plant height, and root-collar diameter (all p 22% under both treatments. Root-collar diameter was strongly associated with overall plant size (R2 = 0.89). Treatment × year interactions were not significant (p > 0.05), providing no statistical evidence of season-specific treatment effects within the three-year trial. Cultivars differed mainly in response magnitude rather than direction. Overall, microalgae applications improved biomass accumulation and root-linked structural traits associated with plant vigor under this production system.
Németh et al. (Thu,) studied this question.