• This meta-analysis evaluates seaweed extracts (SWEs) effects on tomato growth, yield, fruit quality, and physiology compared to untreated controls. • SWEs at 2%–10% concentration significantly improve tomato growth and yield: plant height (+55%), root fresh weight (+58%), and fruit number per plant (+83%). • Fruit quality is enhanced at 2%–10% SWEs dosage, with lycopene (+88%), vitamin C (+83%), and soluble sugars (+111%) increasing compared to untreated controls. • SWEs application is associated with the increasing activities of key antioxidant enzymes (SOD, CAT, PAL, PPO) by 38.8%–120.7%. Seaweed extracts (SWEs) are recognized as environmentally sustainable biostimulants which enhance crop productivity and stress resilience. Here, we conducted a comprehensive meta-analysis of global literature (n = 40 publications) to quantify the integrated effects of SWEs on tomato growth, yield, fruit quality, and physiological traits. The research results show that compared with not applying SWEs, applying SWEs can significantly increase plant height (55.31%) and fresh root weight (57.65%). Within the dataset analyzed in this study, the best effect occurs within the concentration range of 2%–10%. Yield parameters also exhibited concentration-dependent responses: floral initiation and fruit number per plant peaked at 2%–10% (56.32% and 83.34%, respectively), whereas higher concentrations (10%–100%) maximized yield (55.9%) per plant and single-fruit fresh weight (104.04%). Notably, suboptimal concentrations (0%–0.5%) adversely affected yield. Fruit quality attributes, including size and nutritional composition, were most substantially increased from 81.92% to 125.57% under 2%–10% SWEs. The application of SWEs is related to the enhanced activity of key antioxidant enzymes, which play a regulatory role in physiological processes related to stress. In conclusion, SWEs synergistically enhance tomato production sustainability. Within the dataset analyzed in this study, the most significant positive effects are observed in the concentration range of 2% to 10%, which could achieve the balanced effects in promoting tomato growth, increasing yield, ensuring quality, and enhancing physiological adaptability.
Li et al. (2026) studied this question.