Unlocking the potential of tropical red and brown seaweed-based biostimulants—a comparative assessment for sustainable maize (Zea mays) production

The pressing need for sustainable agriculture has led to increasing interest in seaweed biostimulants as a green alternative to chemical fertilizers. This study aimed to investigate and confirm the effectiveness of extracts from two cultivable red seaweeds, Kappaphycus alvarezii (KAE) and Gracilaria debilis (GDE), and a naturally harvestable brown seaweed, Sargassum cinctum (SCE), as biostimulants on maize. The chemical composition showed them to be rich in macronutrients, carotenoids, proline, micronutrients, total phenols, flavonoids, and hormones, many of which have known bioactivities in plants. Field trials were carried out over two years to assess various growth parameters, cob and yield attributes, grain quality, and the status of soil enzymes and nutrients. The findings demonstrated that all three seaweed extracts significantly enhanced plant growth, crop yield, and grain quality. The most effective dosage for maximum benefit was determined to be 7.5%, as further yield improvement was not observed beyond this point. The increases in yields were 19, 21, and 20% over their respective controls in the KAE, GDE, and SCE treatments, respectively, even at the lowest dose of 2.5%. Furthermore, the extracts had positive effects on soil properties, such as increasing enzymatic activities and nutrient availability, which contributed to improved crop nutrition. The active ingredients in the extracts, including plant growth hormones and phenolic compounds, likely influenced plant physiological processes and metabolic pathways, leading to improved shoot and root growth, yield and nutrient absorption. This study highlights the potential of seaweed biostimulants in sustainable agriculture, enhancing productivity, grain quality, soil health and profitability.