Benefits of Seaweed as a Fertiliser

Known as a biofertiliser or biostimulant, seaweed has immense benefits for plant growth. In this post, you will learn about the benefits of seaweed as a fertiliser. Liquid seaweed fertiliser is the most popular choice among gardeners as solid fertilisers take time to become soluble in the soil. 

Seaweed fertilisers contain complex carbohydrates and various other essential minerals that plants need to grow healthily. If you want to avoid using chemical fertilisers and reap the benefits of organic gardening, try using seaweed as it is completely natural and sustainable. 

Read on to know the benefits that plants derive from seaweed fertilisers.

8 Benefits of Seaweed as a Fertiliser

Improves Plant Health by Stimulating Growth

Using seaweed fertilisers can improve the plant’s stress-bearing capacity by improving its overall health. It helps in making the plants more resistant to diseases and pests by boosting their immune systems. Seaweed fertilisers contain naturally occurring growth stimulants that can greatly increase crop yield. 

Seaweed fertiliser is an organic and sustainable way to feed plants. Learn all about seaweed and its benefits for plants as a fertiliser.

Seaweed contains about 70 kinds of minerals and vitamins such as calcium, potassium, phosphorus, magnesium, and iron. A large amount of organic matter present in seaweed provides abundant minerals and stimulates natural growth regulators in plants.

Potassium present in seaweed helps improve the plant’s resistance to extreme temperatures, drought, salinity, and diseases. By thickening the cell walls, potassium helps prevent disease infections. 

Improved Crop Yield

If you want long-lasting fruits and vegetables, introduce seaweed fertiliser to your fertilization schedule for better and healthier produce. It also stimulates growth by promoting budding in flowering plants.  

If applied 10 to 12 days before harvesting, seaweed fertiliser extends the shelf life of fruits and vegetables. It also improves the plant’s resistance to stress conditions like frost and diseases. Some plants like cucumber had an increased yield of almost 40 percent. 

Improves Soil Quality

Seaweed fertiliser works quite well with the soil ecosystem and by increasing the organic matter in the soil, it improves the overall soil consistency and texture. It activates microorganisms present in the soil that act as catalysts thereby increasing the soil quality.

The alginates present in seaweed act as soil conditioners and by reacting with metals in the soil, form cross-linked polymers in the soil. These polymers help retain moisture for a long time keeping the soil aerated and healthy. Alginate is a part of the cell wall that makes seaweed flexible making it resistant to shocks. 


Since seaweed-based fertilisers are derived from organic sources, they are non-toxic and completely safe to use on plants. Fertilisers with seaweed are also harmless to pets and humans and have no harmful effects on the environment. 

Obtained from the ocean, seaweed is completely non-toxic and full of nutrients.

Due to increased awareness about the ill effects of using conventional fertilisers, many gardeners have shifted to more sustainable options such as seaweed. An increase in the demand for biostimulants has led to more people being aware of seaweed, kelp and their benefits. 

Faster Seed Germination

Many scientific pieces of research have proven that seeds soaked in seaweed extract germinates faster and have a larger root mass. Such plants have better growth and high survival rates. Soaking the seeds in seaweed extract reduces the risks related to transplant shock and leads to speedier root growth.  

It has also been found that plants that were fertilized with seaweed produced more flowers per plant. A higher seed germination rate leads to better yields. As a form of mulch, it keeps the soil moist for longer and reduces the amount of water needed. 

Reduces Leaching

Leaching takes place when nutrients get pushed down in the soil out of the root zone. Through rainfall and irrigation, the nutrients are pushed down but over time, they get pushed down so deep into the soil that the plant roots cannot access the necessary nutrients.

Microorganisms present in seaweed exude sticky substances that help bind the nutrients to the soil. These nutrients are then readily available to the plant roots instead of leaching into the lower soil layers. 

Works Well in Hydroponics

Seaweed enriches the plants grown hydroponically by providing the essential nutrients that are generally present in the soil. Kelp is easily absorbed by plant roots leading to more efficient nutrient absorption.

Prevents Pests and Weeds

Seaweed contains salts, the smell and texture of which pests and insects such as slugs, worms, and snails hate. Using seaweed fertilisers also reduces the need to weed the garden. We recommend using liquid seaweed fertiliser as it does not blow away in the wind, unlike dry compost and mulch. 

Ideal Time To Use Seaweed Fertiliser 

You can apply seaweed fertiliser in the early morning or the evening when the temperatures are lower than usual and there is no sunlight. Use it once every two to four weeks for the best growth results. 

You can use seaweed as a whole or as a liquid solution. It can be crushed and composted in the soil. Dried and crushed seaweed meal is commonly composted in the soil.

What Are Seaweed Fertilisers Made of?

Most seaweed fertilisers are made from kelp. Kelp is a brown seaweed variety that grows in shallow saltwater near coastal areas. This variety is rich in nutrients like magnesium, zinc, iron, potassium, and nitrogen. It is known to have more than 70 crucial minerals, vitamins, and enzymes. 

Kelp or seaweed works as an amazing fertiliser for hydroponically grown plants.

Seaweed in itself is not a fertiliser. Instead, it is designed as a root growth stimulant to improve plant performance. Commonly available fertilisers with seaweed are liquid seaweed fertilisers, seaweed extract powder, kelp meal, and calcified seaweed. 

Liquid seaweed fertilisers are prepared from seaweed collected from coastal areas. Saltwater is rinsed and seaweed is allowed to decompose in water until all the solid material gets broken into a liquid. 

Final Thoughts

We cannot speak enough about the immense benefits seaweed holds for your plant’s overall health. A fantastic source of minerals and trace elements, it can greatly improve your plant’s performance. Use it in your garden and get ready to see some impressive growth results. 

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