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

The study, conducted by scientists at the State University of Ponta Grossa and the Federal University of Santa Catarina and published in the journal Blue Biotechnology, tested two commercially available mineral fertilizers enriched with hydrolyzed extracts of the red seaweed Kappaphycus alvarezii and the brown seaweed Ascophyllum nodosum. One product, designated FR and intended for seed treatment, contained 3.0 percent total nitrogen, 10.0 percent P2O5, cobalt, molybdenum, boron, zinc and nickel alongside the algal extracts. The second, designated FG and used as a foliar spray, contained 2.0 percent nitrogen, 2.0 percent P2O5, boron, zinc, sulfur, manganese, magnesium and nickel with the same seaweed extracts.

Alongside these commercial formulations, the researchers prepared aqueous extracts from a blend of three microalgae species grown in their own laboratory: the cyanobacterium Arthrospira platensis, the green microalga Tetradesmus obliquus, and the marine diatom Chaetoceros muelleri. Cultures were grown to the stationary phase in tailored media, harvested by centrifugation, frozen at minus 80 degrees Celsius, lyophilized, and then macerated in deionized water with the pH adjusted to 5.5. The team used 2.5 milligrams of dry biomass from each species per treatment batch, delivering the blend either as a seed coating or as a foliar spray in 150 liters of solution per hectare.

The field experiment took place during the 2023 winter growing season at the Capão da Onça School Farm in Ponta Grossa, Paraná, at roughly 1,002 meters above sea level on a sandy Dystrophic Haplic Cambisol managed under no-till for fifteen years. The researchers employed a randomized block design with four replications in a 3 by 3 factorial arrangement: three seed treatments crossed with three foliar treatments produced 36 experimental units. The barley cultivar Imperatriz was sown at a target density of 2.5 million plants per hectare with base fertilization of 200 kilograms per hectare of 10-20-20 N-P-K and a topdressing of 120 kilograms per hectare of nitrogen at tillering. Foliar applications occurred at 24, 45, 65 and 87 days after sowing, and the 140-day crop cycle was assessed for plant stand, height, stem diameter, tillers, grains per ear, ear length, 100-grain weight and final yield.

The headline result was striking. Seed treatment with the commercial FR product combined with foliar application of the commercial FG product increased barley yield by 49.73 percent, equivalent to 784.24 kilograms per hectare, while the same seed treatment paired with the blended microalgae spray raised yield by 50.53 percent, or 788.84 kilograms per hectare, both compared with untreated controls. Even FR seed treatment alone, when followed by either foliar option, delivered yield gains of roughly 32 percent, translating to approximately 583 to 584 extra kilograms per hectare, or about 9.7 sixty-kilogram sacks.

The physiological story behind these numbers is intricate. FR seed treatment increased the number of tillers per plant by 19.37 percent and plant height by 8.47 percent, likely because the seaweed extracts supply auxin-like, gibberellin-like and cytokinin-like compounds that drive cell division and elongation, while the product’s 10 percent phosphorus content fuels ATP-dependent growth. However, the same treatment shortened ear length by 10.80 percent and reduced 100-grain weight by 5.43 percent. The authors suggest the surge in tillering, and the resulting yield, may partly reflect a compensatory response: unusually heavy early rainfall cut the initial plant stand by 43.13 percent below the intended population, and the sparser crop responded with more tillers and taller plants.

Intriguingly, foliar application alone produced no significant effect on any growth or yield parameter. The researchers attribute this to the formidable physicochemical barriers that dissolved molecules must cross, from the leaf cuticle through the apoplast, before reaching the protoplast of leaf cells. Molecules in the extracts, they note, may simply fail to reach their targets in sufficient concentrations, which helps explain why earlier studies using other growth stimulants reported positive foliar responses in spring barley. The yield benefits in this trial emerged only when the treatments were stacked: the foliar products acted synergistically with FR seed treatment rather than additively, mitigating the seed treatment’s negative effects on ear traits.

The economics look promising on paper. In March 2025 the combined cost of FR and FG was about 14.56 US dollars per hectare, while the extra grain harvested with both products was worth roughly 165 dollars at prevailing prices for a sixty-kilogram sack, a gross gain of about 150 dollars per hectare before labor, fuel and machinery costs. The authors caution, however, that a rigorous economic analysis accounting for all operational expenses remains necessary, and they stress that the FR dose used was based on the manufacturer’s wheat recommendation, since no barley-specific label exists.

The researchers are careful to flag the limitations. Total rainfall over the 140-day cycle hit 1,064.2 millimeters, far above the 450-to-600-millimeter optimum for barley and likely suppressing both disease-free growth and treatment responses, particularly for foliar products. The 100-grain weight averaged 3.79 grams, well below the cultivar’s expected 4.54 grams, and soil conditions were suboptimal. The team therefore calls for multi-year, multi-site trials to confirm the results, alongside deeper investigation into the physiological mechanisms by which macroalgal and microalgal biocompounds—polysaccharides, polyphenols, amino acids, sterols, vitamins and phytohormone mimics—act on germination, tillering and grain filling.

Even with those caveats, the study stands as one of the first field demonstrations that marine macroalgae and freshwater-to-marine microalgae can work together as a coherent biofertilizer system in a temperate cereal crop. With barley demand steady and growers under pressure to cut synthetic inputs, the message from Paraná is that the ocean’s flora, harnessed as seed coatings and leaf sprays, may offer a genuinely scalable route to larger harvests—potentially half again as much grain from the same land, without a single extra kilogram of conventional nitrogen or phosphate.

Subject of Research: Field evaluation of seaweed-extract biofertilizers and blended microalgae extracts for enhancing barley crop growth and yield

Article Title: Seed treatment with seaweed extract biofertilizers and foliar application of blended microalgae extracts enhanced barley (Hordeum vulgare) crop yield

Article References: de Moraes, V. C., Ruivo, L. B., Lopes, R. G., Barboza, L. E., Matiello, R. R., Owatari, M. S., Derner, R. B., & Ohse, S. (2026). Seed treatment with seaweed extract biofertilizers and foliar application of blended microalgae extracts enhanced barley (Hordeum vulgare) crop yield. Blue Biotechnology, 3(1), Article 3. https://doi.org/10.1186/s44315-026-00055-z

Image Credits: AI Generated

DOI: 10.1186/s44315-026-00055-z

Keywords: barley, Hordeum vulgare, biofertilizers, biostimulants, seaweed extract, Kappaphycus alvarezii, Ascophyllum nodosum, microalgae, Arthrospira platensis, Tetradesmus obliquus, Chaetoceros muelleri, sustainable agriculture