Plant biostimulants are innovative products designed to enhance plant growth and resilience through mechanisms beyond simple nutrient supply. According to the European Union (EU) definition, these products stimulate plant nutrition processes, aiming to improve nutrient use efficiency, stress tolerance, quality traits, and soil nutrient availability (EU, 2019). One prominent category of plant biostimulants is seaweed extracts, which are derived from various seaweed species including brown, red, and green seaweeds. These extracts undergo diverse extraction processes—alkaline, neutral, or acidic aqueous extractions, high-pressure milling, and cryo-grinding, among others (Goñi et al., 2020; Sujeeth et al., 2022).
The global market for non-microbial plant biostimulants, including seaweed-based products, was valued at approximately $2.54 billion in 2021 and is projected to grow steadily. In 2021, seaweed-based plant biostimulants alone accounted for $758 million, making up about 30% of the market share (Dunham-Trimmer, 2022). With the new Fertilising Products Regulation enacted in July 2022, which facilitates the introduction of plant biostimulants into the European Union market, the use of seaweed-based products is anticipated to increase further.
Seaweeds have been utilised historically to enhance soil fertility and crop productivity, particularly in coastal regions. Early observations linked their benefits to nutrient supply and improved soil conditions. Today, scientific research supports these benefits, highlighting several key effects of seaweed-based plant biostimulants:
1. Enhanced Growth and Stress Tolerance: Studies show that seaweed extracts can stimulate rooting, enhance chlorophyll content, and improve stress tolerance (Ferrante et al., 2013; Rasul et al., 2021). For instance, extracts from Ascophyllum nodosum have demonstrated the ability to mitigate drought stress by modulating gene expression related to stress response and growth (Rasul et al., 2021; Cocetta et al., 2022).
2. Improved Nutrient Use Efficiency: Seaweed extracts can enhance nutrient uptake and reduce the need for chemical fertilisers. Research indicates that A. nodosum extracts can reduce nitrogen fertiliser applications by up to 27% while maintaining or increasing crop yields (Goñi et al., 2021).
3. Biochemical and Molecular Effects: Seaweed-based biostimulants influence various biochemical pathways and gene expressions in plants. For instance, polysaccharides from seaweeds have been linked to enhanced nutrient efficiency and stress tolerance through modulation of plant metabolic pathways (Carmody et al., 2020; Sujeeth et al., 2022).
What poses regulatory challenges to the use of seaweed extracts?
The growing popularity of seaweed-based plant biostimulants brings several regulatory challenges, particularly concerning their approval and market access. To address these issues, EBIC released a whitepaper on the use of seaweed as a biostimulant.
The EU Fertilising Products Regulation, which came into effect in July 2022, provides a standardised framework for the registration and marketing of plant biostimulants. However, this regulation requires comprehensive documentation and validation of the efficacy and safety of seaweed-based products, which can be resource-intensive.
Despite promising research, the regulatory approval process demands robust scientific evidence to substantiate claims made by biostimulant products. This includes demonstrating the specific mechanisms through which seaweed extracts enhance plant growth and resilience.
The efficacy of seaweed-based plant biostimulants can vary based on extraction methods and seaweed species used. Regulatory bodies require consistency and reliability in product performance, necessitating detailed characterisation of each product’s composition and effects.
As the market for plant biostimulants expands, companies face the challenge of navigating varying national regulations and standards within the EU. This can impact the timely and cost-effective introduction of innovative seaweed-based products to market.
Recent advancements in the understanding of seaweed-based plant biostimulants underscore their potential to enhance plant growth and resilience through complex biochemical mechanisms, independent of traditional plant hormones. Despite their benefits, regulatory hurdles pose significant challenges for their widespread adoption. Continued research and clear regulatory guidelines will be crucial in advancing the development and application of these innovative biostimulants.