Main Article Content
Lettuce production in the winter on the Adriatic coast, especially in a non-heated plastic tunnel, requires longer cultivation and is characterised by lower head mass and yield. In these conditions, the effect of biostimulant Bio-algeen S-90 and fertilizer Megagreen on the production of the traditional winter lettuce cultivar ‘Four Seasons’ was tested. Both treatments showed a positive effect on the growth and total yield of winter lettuce, and decreased the share of non-marketable yield. Bio-algeen S-90 treatment increased the plant height by 61.5%, and foliar treatment with Megagreen by 60.9%, as compared to the control treatment. Equally, both treatments resulted in higher leaf numbers (47.7% for Bio-algeen S-90 and 37.2% for Megagreen). The head mass of lettuce treated with Bio-algeen S-90 and Megagreen was 30.3% and 25.0% higher than in the control treatment, respectively. Megagreen contributed more to chlorophyll and carotenoid content, while Bio-algeen S-90 elevated the amount of vitamin C and dry matter. The pH value of lettuce juice decreased after Bio-algeen S-90, while the mineral content (N, P and K) did not differ between the tested treatments. Lower nitrate content was detected after both treatments. The obtained results elucidate the effect of Bio-algeen S-90 and Megagreen on “low input” lettuce production.