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