Seaweed/Kelp: for Agriculture and Horticulture: A Natural Biostimulant Powerhouse

Written By Aicx

Seaweed and kelp-based fertilisers

They are natural biostimulants derived from marine algae, particularly brown seaweeds like Ascophyllum nodosum.

What is Seaweed or Kelp Fertiliser?

Seaweed and kelp-based fertilisers are natural biostimulants derived from marine algae, particularly brown seaweeds like Ascophyllum nodosum. These are harvested from nutrient-rich ocean environments and processed into liquid, powder, or granulated products for agricultural and horticultural use.

Unlike traditional NPK fertilisers, seaweed doesn’t just feed plants—it enhances the plant's metabolic functions, stimulates soil biology, and improves stress tolerance, making it a valuable tool in both conventional and regenerative farming systems.

What Makes Seaweed So Effective?

For centuries, seaweed has been used as a natural plant tonic. However, in the past few years, science has revealed the real reason it works so well: naturally occurring growth regulators, amino acids, and trace minerals that enhance plant performance on multiple fronts.

Key Components That Drive Seaweed’s Performance:

🌿 Natural Plant Hormones:

  • Cytokinins – Stimulate cell division and delay senescence

  • Auxins – Encourage root growth

  • Gibberellins – Promote flowering and shoot elongation

⚛️ Amino Acids:

  • Essential for enzyme production, photosynthesis, and stress recovery.

💧 Mannitol:

  • A sugar alcohol that acts as a natural chelating agent, improving the availability of trace minerals to plants.

🌱 Micronutrients:

  • Seaweed contains more than 60 minerals, including:

    • Iron, Zinc, Manganese, Copper, Molybdenum, Boron, and Cobalt

🧪 Alginates & Complex Sugars:

  • Improve soil structure, water retention, and promote a healthy root microbiome.

Benefits of Seaweed for Plants and Soil

✅ For Plants:

  • Improved germination and seedling establishment

  • Increased root development and nutrient uptake

  • Enhanced flowering, fruit set, and yield

  • Better resistance to drought, frost, and disease

  • Faster recovery from environmental stress

✅ For Soil:

  • Feeds and supports beneficial microbes in the rhizosphere

  • Improves soil structure and aeration

  • Increases moisture-holding capacity

  • Enhances the availability of nutrients already in the soil

Why Ascophyllum nodosum is the Gold Standard

Ascophyllum nodosum, native to cold North Atlantic waters, is regarded as one of the most potent seaweed species for agriculture. It has evolved to survive extreme environmental stress, and this resilience is passed on to plants through its use.

It contains:

  • Over 70 minerals

  • 17 amino acids

  • 4 natural growth regulators

  • Powerful chelating agents and alginates

These compounds help activate soil microbes, enhance nutrient cycling, and strengthen plant immune systems—leading to better yields, improved quality, and superior resilience.

Combine Seaweed with Liquid Fertilizers for Even Greater Results

Adding seaweed extract to your liquid fertiliser—such as Liquid N or N+S blends from Vernado—supercharges the performance of both the fertiliser and the plant.

🌾 Synergistic Benefits:

  • Increased nutrient uptake – Seaweed improves root absorption and stomatal activity, allowing nitrogen and sulphur to be absorbed more efficiently.

  • Reduced stress – Plants under nitrogen boost can be prone to stress. Seaweed moderates the uptake curve, supporting more balanced growth.

  • Boosted biological activity – When combined with liquid fertilisers, seaweed feeds soil microbes, improving nutrient cycling and microbial resilience.

  • Enhanced growth response – The natural growth hormones in seaweed amplify the vegetative response typically seen with Liquid N applications.

By combining seaweed extract with your base fertiliser, you’re not just feeding the plant—you’re also stimulating root growth, supporting soil life, and improving the plant’s ability to resist disease and environmental extremes.

Explore our fertiliser range at Vernado Fertiliser Solutions to learn how seaweed can be integrated into your crop nutrition program.

Application Methods

Seaweed is highly flexible and compatible with most farming systems. Recommended methods include:

  • Foliar Spray – Rapid absorption through leaf stomata

  • Soil Drench – Boosts root and microbial activity

  • Seed Treatment / Dip – Enhances establishment

  • Fertigation / In-Furrow – Seamless integration with liquid applications

Tip: Regular, small doses throughout the growing season yield better long-term results than large one-off applications.

Organically Approved and Environmentally Friendly

Most seaweed-based products are approved for organic farming, making them ideal for environmentally conscious growers. They support soil regeneration and help reduce dependence on synthetic inputs, aligning well with regenerative and sustainable farming practices.

Look for certifications like BioGro NZ or NZS 8410 when selecting products.

Final Thoughts

Seaweed and kelp extracts—especially from Ascophyllum nodosum—are much more than a foliar feed. They act as powerful biostimulants, plant strengtheners, and soil enhancers, delivering better root development, higher resilience, and stronger yield potential.

When added to liquid fertilisers like Liquid N or N+S, seaweed creates a high-performance blend that not only feeds your crops but supports long-term soil and plant health.

Ready to Harness the Power of Seaweed?

Whether you’re growing pasture, maize, brassicas, or horticultural crops, we can help integrate seaweed into your fertility program.
📞 To discuss your crop needs or request a product sample, click the link below:

Aicx
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