Seaweed Is Quietly Reshaping Global Farming, and the Science Is Catching Up Fast

Marine macroalgae, better known to most of us as seaweed, are quietly becoming one of the most talked-about tools in the push for sustainable farming. A new bibliometric review published in Discover Agriculture has mapped two decades of global research on seaweed-based soil amendments and biostimulants, and the picture it paints is striking: scientific output on the topic has grown at an average annual rate of 11.94 percent between 2000 and 2024, with a sharp acceleration after 2018 and a record 30 publications in 2024 alone. The analysis, led by Sukamal Sarkar and colleagues at the Ramakrishna Mission Vivekananda Educational and Research Institute in Kolkata, India, distills a sprawling, interdisciplinary field into a coherent evidence base for researchers, policymakers, and agribusiness.

The team searched the SCOPUS database using a deliberately stringent four-domain strategy, requiring studies to simultaneously address seaweed or marine algae, specific crop types, yield and productivity parameters, and nutrient uptake or soil fertility. From more than 55,000 seaweed-related records and over a million crop-focused publications in the database, the intersection yielded just 156 non-redundant English-language journal articles. That narrow funnel was intentional, the authors explain, because it captured only research sitting squarely at the soil–crop–nutrient nexus rather than the broader universe of algal science. A parallel search in Web of Science returned 139 articles with roughly 89 percent overlap, lending confidence that the core literature was well captured.

Geographically, the field is dominated by Asia, which produced 84 of the 156 papers, with India alone contributing 41. Europe followed with 41 publications, led by Italy, Greece, and Portugal, while North America added 12. The authors attribute Asia’s leadership to abundant coastal biodiversity, long-standing cultural use of marine biomass in farming, and national programs encouraging bio-input adoption. Europe’s output, they note, has been stimulated by the EU Fertilising Products Regulation, which formally recognized biostimulants as a product category in 2019. Africa and South America remain strikingly underrepresented, a gap the researchers link to limited marine access, infrastructure, and research funding rather than any lack of agronomic potential.

What exactly makes seaweed so valuable to crops? The answer lies in a dense cocktail of bioactive compounds. Brown seaweeds such as Ascophyllum nodosum contain alginates, laminarin, and fucoidan; red species like Kappaphycus alvarezii and Gracilaria supply carrageenan and agar; green algae such as Ulva contribute their own sulfated polysaccharides. Layered on top are phytohormones including auxins, cytokinins, and gibberellins, along with betaines, phenolic antioxidants, amino acids, and micronutrients. Together, these molecules modulate plant physiology at multiple levels, from photosynthetic efficiency to the expression of nutrient transporter genes in root membranes.

The molecular evidence is particularly compelling. Transcriptomic analyses show that seaweed extracts reprogram key metabolic pathways, including phenylpropanoid and flavonoid biosynthesis, and upregulate genes tied to photosynthesis, hormone signaling, and carbon, nitrogen, and sulfur metabolism. In rapeseed, Ascophyllum nodosum extract improved nitrogen and sulfur acquisition by boosting the transcription of root membrane transporters for those nutrients. Betaines in the extracts appear to inhibit chlorophyll degradation, preserving photosynthetic capacity, while enhanced activity of enzymes like Rubisco and carbonic anhydrase supports greater carbon assimilation and starch biosynthesis.

Field results back the laboratory findings. Seaweed sap applied as a foliar spray or soil drench has boosted yields in rice, wheat, maize, green gram, tomato, kiwifruit, and citrus across multiple studies. One trial reported a nearly 19 percent grain yield increase in boro rice with Ascophyllum-derived biostimulants compared to untreated controls. Nutrient uptake enhancements ranged from modest 7 to 11 percent gains in potato tubers to extraordinary responses exceeding 200 to 400 percent in sesame, though the authors caution that this variability reflects species-specific and application-dependent differences. Notably, most experimental evidence comes from India, where Kappaphycus alvarezii and Gracilaria edulis dominate the literature, raising generalisability concerns that the review flags explicitly.

Beyond the plant itself, seaweed amendments reshape the soil. Polysaccharides like alginate form gel-like matrices that improve soil aggregation, aeration, and moisture retention, while humic and fulvic acids in seaweed sap buffer soil pH. The amendments also feed rhizosphere microbial communities, including nitrogen-fixing bacteria and phosphorus-solubilizing fungi, accelerating organic matter decomposition and nutrient mineralization. Seaweeds even act as chelating agents, adsorbing heavy metals from contaminated soils and shielding crops from toxicity. Under stress conditions, seaweed extracts help plants maintain favorable potassium-to-sodium balances under salinity, preserve leaf turgor during drought, and activate salicylic acid and jasmonic acid signaling pathways that prime defenses against pathogens.

The thematic mapping revealed four dominant research clusters: algal physiology and bioactive mechanisms, seaweed-based inputs for yield and nutrition, soil health and organic amendments, and biofertilizers combined with stress adaptation strategies. Temporal clustering showed the field’s evolution from taxonomic and foundational algal studies in the early 2000s toward applied agronomic research after 2010, and finally toward integrated soil health and climate-smart agriculture in recent years. The post-2018 surge in soil health and biofertilizer research coincides with the EU regulation and the launch of the UN Decade of Ecosystem Restoration, suggesting policy is actively steering the science.

Economically, the picture is promising but incomplete. Commercial products such as Stimplex, Kelpak, Maxicrop, and Sagarika have achieved market penetration, and studies on rice and maize in India reported net returns exceeding 15 to 25 percent above conventional fertilizer-only treatments. Yet comprehensive techno-economic assessments for smallholder contexts in South Asia and sub-Saharan Africa remain scarce, and production costs hinge heavily on harvesting methods, extraction technology, and formulation type. Integrating seaweed processing into coastal biorefineries, where co-products like agar and carrageenan offset costs, offers one pathway to economic sustainability within a circular bioeconomy.

The review’s authors are candid about remaining gaps: standardized application protocols, multi-location field trials across diverse agroclimatic zones, multi-omics elucidation of molecular mechanisms, life-cycle assessments, and systematic screening of underutilized red and green seaweed species all demand attention. Still, the trajectory is unmistakable. As agriculture grapples with soil degradation, nutrient leaching, and climate volatility, seaweed-based amendments offer a rare combination of benefits, feeding crops, restoring soils, and supporting microbial life, all from a renewable marine resource. The evidence base is now consolidated; the challenge ahead is translating it into reproducible, affordable practice at farm scale.

Subject of Research: Bibliometric analysis of global research trends on seaweed-based soil amendments and biostimulants for crop productivity and soil health from 2000 to 2024

Article Title: Global research trends on seaweed-based amendments for soil health and crop productivity

Article References: Sarkar, S., Dutta, S., Dey, S., Dhar, A., Garai, S., Ghosh, S., Brahmachari, K., & Ghosh, A. (2026). Global research trends on seaweed-based amendments for soil health and crop productivity. Discover Agriculture, 4(1), Article 289. https://doi.org/10.1007/s44279-026-00741-x

Image Credits: AI Generated

DOI: 10.1007/s44279-026-00741-x

Keywords: seaweed, biostimulants, soil health, crop yield, sustainable agriculture, macroalgae, biofertilizers, nutrient uptake, bibliometric analysis, Ascophyllum nodosum, Kappaphycus alvarezii, climate-smart agriculture