Your Comprehensive Guide to Seaweed Fertilizer: Types, Benefits, and Agricultural Uses
Table of Contents
- The Global Importance of Seaweed and Algae
- Benefits of Seaweed for Plants
- Types of Seaweed
- Seaweed Used in Agriculture
- Unique Chemical Compounds in Brown Seaweed
- Benefits of Seaweed Fertilizer
- How to Use Seaweed Fertilizer
The Global Importance of Seaweed and Algae
Seaweed, including macroalgae and microalgae, contributes to approximately 30% of global aquatic production, offering social and economic benefits to coastal communities. Seaweed plays a crucial role in enhancing human and environmental health. The diverse contributions of seaweed and microalgae to human health, environmental benefits, and ecosystem services have increasingly drawn attention to the untapped potential of seaweed and microalgae cultivation.
Benefits of Seaweed Fertilizer for Plants
Since the 1950s, seaweed extracts have been used as biostimulants. These extracts enhance plant growth, increase crop productivity, improve product quality, and boost plants’ resistance to abiotic stress and diseases.
Seaweed extracts stimulate physiological responses in plants, such as:
- Enhancing plant growth.
- Increasing tolerance to various abiotic stresses (salinity, drought, frost).
- Reducing the severity of fungal, viral, and insect infections.
- Improving flowering and crop yield.
- Enhancing the quality and nutritional content of edible products.
- Extending product shelf life.
Types of Seaweed
Seaweed, commonly known as macroalgae, is classified into three main groups based on color:
- Brown Algae (Phylum: Ochrophyta, Class: Phaeophyceae)
- Red Algae (Phylum: Rhodophyta)
- Green Algae (Phylum: Chlorophyta; Classes: Bryopsidophyceae, Chlorophyceae, Dasycladophyceae, Prasinophyceae, Ulvophyceae)
Seaweed varies significantly in biochemical composition, including pigment content, storage compounds, cell wall composition, presence or absence of flagella, cell division methods, intercellular communication structures, and chloroplast structure.
Seaweed Used in Agriculture
The most commonly used seaweed species in agriculture include:
- Green algae: Azolla, Spirulina
- Brown algae: Ascophyllum, Ecklonia, Ectocarpus, Fucus
There are about 1,800 species of brown algae, most of which are marine. Brown algae are generally larger in size and predominantly found in cold waters. They contain varying amounts of chemical components that play a vital role in plant physiology, microbial soil communities, and antimicrobial properties, making brown seaweed the most commonly used in seaweed-based fertilizers.
Unique Chemical Compounds in Brown Seaweed
Brown seaweed, such as Ascophyllum, contains key compounds including:
- Macronutrients: Phosphorus, Potassium, Calcium, Magnesium, Sulfur
- Micronutrients: Boron, Iron, Manganese, Zinc
- Free Amino Acids: Glycine, Alanine, Valine, Methionine, Isoleucine, Threonine, Cysteine, Phenylalanine, Serine, Lysine, Glutamic Acid, Aspartic Acid, Arginine, Hydroxyproline
- These aid in balanced plant growth, improved nutrient uptake, stress resistance, root development, and enhanced chlorophyll concentration.
- Simple Sugars and Sugar Alcohols: Provide energy for protein synthesis and boost plant defense mechanisms.
- Plant Hormones (Cytokinins, Auxins): Delay senescence, prevent leaf and fruit drop, maintain chlorophyll levels, promote cell division, encourage root growth, and enhance storage capacity in leafy crops like lettuce and parsley.
- Alginic Acid: Released from seaweed cell walls during extraction, forming water-soluble chelates of minerals (Fe, Zn, Mn, Mg, Ca), improving nutrient availability.
- Laminarin: Stimulates plant immune responses.
- Fucose-Containing Polysaccharides (FCPs): Possess antiviral and antioxidant properties.
- Vitamins: Thiamine (B1), Riboflavin (B2), B12, Vitamin C, which regulate plant growth, enhance photosynthesis, and promote root development.
Average Chemical Composition of Ascophyllum Nodosum (Pereira et al., 2020)
- Water: 12–15%
- Cellulose: 8%
- Ash: 17–20%
- Protein: 5–10%
- Alginic Acid: 20–29%
- Fucoidan: 19%
- Mannitol: 5–8%
- Laminarin: 2–36%
- Carotene: 30–60 mg/kg
Macronutrients:
- Phosphorus: 0.1–1.15%
- Potassium: 2–3%
- Calcium: 1–3%
- Magnesium: 0.5–0.9%
- Sulfur: 2.5–3.5%
Micronutrients:
- Iron: 150–1,000 mg/kg
- Manganese: 10–50 mg/kg
- Zinc: 50–200 mg/kg
- Boron: 40–100 mg/kg
- Molybdenum: 0.3–1 mg/kg
- Sodium: 3–4%
Trace Elements:
- Cobalt: 1–10 mg/kg
- Iodine: 700–1,200 mg/kg
- Nickel: 2–5 mg/kg
- Barium: 15–50 mg/kg
Vitamins:
- Vitamin C: 500–200 mg/kg
- Vitamin A: 30–60 mg/kg
- Vitamin K: 10 mg/kg
- Vitamin E: 150–300 mg/kg
- Folic Acid: 0.1–0.5 mg/kg
Vitamin B Complex:
- B1: 15 mg/kg
- B2: 5–10 mg/kg
- B3: 10–30 mg/kg
- B6: <1 mg/kg
- B7: 0.1–0.4 mg/kg
- B12: 0.004%
- B9 (Folic Acid): 0.1–0.5 mg/kg
How to Use Seaweed Fertilizer
Seaweed fertilizer can be applied directly to plant leaves or added to soil around plant roots. It can also be used for seed soaking before planting to improve germination. Regular application throughout plant growth stages enhances development and increases resilience against environmental stress.
The highest recorded concentration of Ascophyllum nodosum in a fertilizer formulation is found in ForalgBMO by AsfertGlobal (Portugal), making it the most potent and effective product for promoting plant growth and resilience.
References
Cai, J., Lovatelli, A., Aguilar-Manjarrez, J., Cornish, L., Dabbadie, L., Desrochers, A., Diffey, S., Garrido Gamarro, E., Geehan, J., Hurtado, A., Lucente, D., Mair, G., Miao, W., Potin, P., Przybyla, C., Reantaso, M., Roubach, R., Tauati, M. & Yuan, X. (2021). Seaweeds and microalgae: An overview for unlocking their potential in global aquaculture development. FAO Fisheries and Aquaculture Circular No. 1229. Rome, FAO. https://doi.org/10.4060/cb1229
