Page 1

Seaweed A Precious Material for Plant Nutrition

by Luis Bartolo

Seaweed has been harvested for food, fertilizer and medicine for thousands of years. History books record that the Chinese used seaweed for medicinal purposes as early as 3000 B.C. The Greeks for example used seaweed as animal food as early as the first century B.C. One translated text written in 46 B.C states: "The Greeks collected seaweed from the shore and having washed it in fresh water, gave it to their cattle." Today China and Japan are the biggest consumers of seaweed worldwide, with China harvesting 500 million tons a year for food use alone.


MAXIMUM YIELD USA - September 2009

Seaweed has been as a source of organic material to add to soil or soilless cultivation. It is only during the latter half of the last century that techniques were developed to fully understand the physiological responses which seaweed clearly produces. Parallel to laboratory and industrial studies to characterize and understand seaweed, techniques were developed to extract and concentrate active ingredients used to influence the plant physiology. So the use of seaweed in agriculture has moved from using a simple dried product, which was harvested by hand and spread on the soil, to distribution of so called seaweed derived products manufactured into small dried flakes, suspensions or solutions containing active ingredients produced from the seaweed raw material.

But what is seaweed exactly? In the classification of all living things, seaweed is classified within the ‘plant’ group, although they are apparently a little behind in evolutionary terms compared with the more familiar plants seen every day. Seaweed may belong to one of several groups of multicellular algae: the red algae, green algae and brown algae. As these three groups are not thought to have a common multicellular ancestor, the seaweeds are a paraphyletic group. In addition, some tuft-forming blue green algae (Cyan bacteria) are sometimes considered as seaweeds. "Seaweed" is a colloquial term and lacks a formal definition. Botanists refer to these broad groups as Phaeophyceae, Rhodophyceae and Chlorophyceae, respectively. Brown seaweeds are usually large, and range from the giant kelp that is often 65 feet long, to thick, leather-like seaweeds from six to 13 feet long, to smaller species 11 to 23 inches long. Red seaweeds are usually smaller, generally ranging from a few inches to about three feet in length; however, red seaweeds are not always red. They are sometimes purple, even brownish red, but they are still classified by botanists as Rhodophyceae because of other characteristics. Green seaweeds are also small, with a similar size range to the red seaweeds. Seaweed contains all known trace elements. These are present in a form that is acceptable and available to plants. Trace elements can be made available to plants by chelating - that is, by combining the mineral atom with organic molecules.

Effect of Seaweed Research shows that high quality seaweed extracts can have a five-principle effect on plant growth. All of them remove or reduce the influence of a number of growth constraints, with the result that treated plants function better, and produce higher yields and better quality crops. Seaweed supplies all trace elements required for plant growth across the entire spectrum. Seaweed and seaweed products also exert some form of biological control over a number of common plant diseases such as pythium. Soil fungi and bacteria are known to produce natural antibiotics which hold down the population of plant pathogens, and when these antibiotics are produced in sufficient quantities, they enter the plant and help it to resist disease. The production of such antibiotics is increased in soil high in organic matter, and it may be that seaweed still further encourages this process. Seaweed also acts as a soil conditioner. It has the ability to transform light and sandy soils into denser mediums by creating organic polymars which bind the soil particles together. This creates better structure and also assists in water retention.

Immune system: A regular application to the foliage of plants induces Localised Acquired Resistance (LAR) against a range of fungi, bacteria and viruses. There are indications that this effect may also be systemic. Applications also improve the plant's ability to withstand certain levels of environmental stresses and reduce the attacks and flare-ups of sap-sucking insect pests on the plants. As well as resistance to frost through this method, a localised resistance to heat stress can also be utilized by the plant through the application of seaweed. The plant’s cells respond to the seaweeds nature of existing in deep cold, helping the plant to cool down.

MAXIMUM YIELD USA - September 2009


Seaweed: A Precious Material for Plant Nutrition

"Applied to plants that can cold acclimatize, seaweed extract initiates or speeds up the acclimatization process even when the plant is not subjected to a cold stress." Chlorophyll: Foliar application of seaweed extracts will result in greater maintenance of chlorophyll, leading to greener plants. This is in part due to a complex family of different betaines in the seaweed extract, which help reduce natural damage to the photosynthetic process. Research has shown that application through foliar sprays and watered into the growing medium has the same effect on enhanced chlorophyll, and in most cases produced actual higher levels of chlorophyll in the plants.

Microbes: Specific carbohydrates in seaweed extracts serve as a source of food for beneficial and benign soil bacteria, resulting in a large increase in microbe numbers. These microbes produce plant growth stimulating compounds that encourage root growth and a significantly larger root mass. The increased bacterial population can also both physically exclude and compete with potential plant pathogenic soil fungi. Research has proven that seaweed contains qualities that make plants more resistant to insect and fungal disease. The activation of the natural microbial structure of the soil or medium in combination with all trace elements makes the plant stronger and better able to deal with attacks. The carbohydrates in seaweed and seaweed products work in natural combination with the iron, cobalt, copper, manganese, zinc and other trace elements. That is why these trace elements in seaweed and seaweed products do not settle out, even in alkaline soils, but remain available to plants which need them at all times.

Nematodes: The complex range of compounds found within seaweed extracts can help reduce nematode damage. This includes a reduction in hatch and a disorientation or simple 'burn-out' of immature nematodes (J2s), minimizing root penetration.

Frost: Applied to plants that can cold acclimatize, seaweed extract initiates or speeds up the acclimatization process even when the plant is not subjected to a cold stress. This allows plants to tolerate greater levels of cold, reducing the amount of damage. As you can see seaweed is one of the unique organic compounds that can be used in agriculture in many different ways. Beside the immune system the usage of seaweed has a lot of benefits: • beneficial for the environment • does not harm birds or any other animals • increases root depth and branching • fortifies the plant’s natural defenses • increases plant’s nutrient absorption capacities • improves color/quality of vegetables, ornamentals or lawn • breaks down large organic molecules into easier to absorb subunits MY Learn more about natural nutritional alternatives including seaweed at under our article archive.


MAXIMUM YIELD USA - September 2009

Sea Weed  
Sea Weed  

by Luis Bartolo 100 MAXIMUM YIELD USA - September 2009 Effect of Seaweed 101MAXIMUMYIELDUSA - September 2009