Harnessing the power of microalgae consortia for sustainable crop production: case study on lettuce (Lactuca sativa L.)

Due to global food demand and need to protect the environment, improving crop productivity while reducing agrochemical use has become crucial. Microalgae offer a potential solution as they exhibit biostimulant and biofertilizer effects, improving both crop and soil quality. This study aimed to assess the impact of suspensions of freeze-dried Chlorella vulgaris (UTEX 265), Scenedesmus obliquus (UTEX 393), and Haematococcus pluvialis (UTEX 2505) biomass in distilled water on lettuce (Lactuca sativa L.) germination and development. Different microalgae treatments, individually and mixtures, were applied. The study evaluated various plant growth parameters and the concentration of nutritional constituents, including reducing sugars, total polyphenols, antioxidant capacity, and chlorophyll a. In the first stage (germination), microalgae treatments (C. vulgaris 2 g (CV2),; C vulgaris 0.66 g, S. obliquus 0.66 g and H. pluvialis 0.7 g (CV0.7:SO0.7:HP0.7) and C. vulgaris 1.5 g and S. obliquus 1.5 g (CV1.5:SO1.5) increased L. sativa seed germination rate and the number of germinated seeds. Significant changes were observed in growth-related variables such as height (CV0.7:SO9.7:HP0.7), stem diameter (C. vulgaris 3 g (CV3)), root length (S. obliquus 3 g (SO3)), and leaf area (CV1.5:SO1.5). In the second stage (plant development), microalgae treatments significantly increased dry weight from 2.71% (CV1.5:SO1.5) to 48.52% (SO3), reduced sugars from 3.20% (CV3) to 59.05% (CV1.5:SO1.5), total polyphenols from 7.99% (CV3) to 40.15% (CV1.5:SO1.5), antioxidant capacity from 0.77% (CV0.7:SO9.7:HP0.7) to 17.40% (CV1:HP1), and chlorophyll a from 23.01% (CV1.5:SO1.5) (p ≤ 0.05). C. vulgaris and S. obliquus in blending were identified as the main microalgae promoting positive effects on L. sativa development. This study confirms that microalgae, particularly C. vulgaris and S. obliquus, can enhance crop quality, specifically in L. sativa. These findings demonstrate the potential of microalgae as biostimulants, supporting their application to improve crop productivity and emphasizing their role in sustainable agriculture.