Biostimulants from Marine Algae

Marine algae have been used since ancient times, either directly or in composted form, as soil conditioners. In recent years, they have been intentionally incorporated into products as biostimulants or biofertilizers. The use of various marine algae species offers a promising alternative to conventional fertilizers and a potential solution to current agricultural challenges.

Marine algae are a large and diverse group of plants. Some consist of just a single cell, while others can grow to great lengths. All are capable of photosynthesis. For biostimulant and biofertilizer applications, brown algae are predominantly used worldwide.

Marine algae are rich in nutrients and natural growth hormones and can fix atmospheric nitrogen, making them an excellent source of organic matter for improving soil.

Biostimulants can provide at least one of the following plant or rhizosphere benefits (Yakhin et al., 2017):

• Nutrient use efficiency (availability, uptake)
• Tolerance to abiotic stress
• Quality traits (flower count, root length, root density)
• Availability of bound nutrients in the soil or rhizosphere

Brown algae are mainly found along the North Sea coasts of Europe, the northern Atlantic, and Greenland. Their habitat is tidal, so Ascophyllum nodosum alternates between being submerged and exposed to air. Ascophyllum nodosum is rich in nitrogen, potassium, phosphorus, and trace elements such as iron and manganese. Due to its high concentrations of cytokinins and gibberellins, it directly stimulates vegetative growth, flowering, and fruit set. Auxins, in contrast, are found in higher amounts in Ecklonia maxima (kelp), which directly stimulates root growth. Ascophyllum nodosum also contains significant levels of mannitol, betaine, vitamins, alginic acid, and amino acids.

When used as a biofertilizer, brown algae can improve soil fertility, stimulate root growth, and increase crop yield. As biostimulants, they also enhance vegetative growth, vitality, flowering, and fruit set, mainly by improving nutrient uptake. Ascophyllum nodosum can boost plant resilience against abiotic stresses such as extreme temperatures, drought, waterlogging, or frost. Processing Ascophyllum nodosum improves soil swelling and crumb formation and has been shown to increase cation exchange capacity.