Synergistic effect of cultivation methods and seaweed-based biostimulations on iceberg lettuce in sustainable agriculture

This research, conducted over two consecutive years in the production fields of the Iceberg Lettuce Centar in Belgrade, aimed to investigate the impact of biostimulants on the morphological and phytochemical characteristics of iceberg lettuce in two seasons (spring and autumn), using greenhouse and open field cultivation. The biostimulator was derived from a seaweed (Kelpak). The effects of different applications (seedling soaking and foliar treatment once, twice, and three times during the growing season) on plant growth (total plant mass, leaf mass, and stem mass) and phytochemical properties, including pigments (chlorophyll a, chlorophyll b, carotenoids), as well as antioxidant activity (TAC, polyphenols), were investigated. The results showed that the application of biostimulators, particularly through the seedling soaking method, contributed to an increase in plant mass and greater biomass accumulation, whereas foliar treatments enabled better development in both seasons. Plants grown in the greenhouse had more stable growth and better quality, while the spring season proved to be more favourable than autumn. Biostimulators also had a positive effect on the content of photosynthetic pigments and antioxidants, which improved the nutritional value and stress resistance of plants.