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compost seaweed

Compost seaweed

Seaweed contains plant nutrients, including potassium, (up to 12%) , but it is low in nitrogen and phosphate. It can contain in the region of 60 trace elements, growth hormones and other nutrients particularly rich in iodine and calcium. Spraying seaweed tea is said to increase resistance to insect infestation. Seaweed has been used as a soil improver for centuries and is still used in the garden as a mulch, liquid feed and in making compost. It is also available commercially both dried and as a liquid.

If considering collecting seaweed it must be noted that many countries have laws or regulations protecting the marine environment and it is likely that these will cover the harvesting of seaweed.

In the UK the Crown Estate licenses sustainable, commercial harvesting of seaweed from areas of foreshore and seabed not privately owned. However, while commercial harvesting of seaweed from areas of Crown Estate foreshore or seabed requires a licence, collection for personal use, in small qualities does not require a licence but the permission of the landowner will be required.

Composting seaweed

Seaweed is a commonly used as a constituent in home composting in coastal areas. It acts as an activator speeding up the compost process. If using a cold composting technique small quantities of seaweed can just be added to the bin in the same way as any other nitrogen rich “green”. There are mixed views as to whether the seaweed should be washed to remove traces of saltwater or sand with the consensus being that it is not necessary. However, not all plants tolerate salt so if in doubt the seaweed should be rinsed in fresh water.

If using a New Zealand or pallet bin, in which layers of greens and browns are alternated, the seaweed can be added as a separate green layer or mixed with other green material. Shredded or chopped seaweed cut in 1- or 2-inch will decompose in a few weeks compared with six months or more for uncut fronds so, as with other materials, it is better to cut the seaweed into small pieces. If the contents of the bin are to be turned to aerate the organic material occasionally in cold composting or regularly as in hot composting cutting the seaweed into short lengths will also make it easier to turn during aeration and speed up the composting process.

Seaweed contains plant nutrients, including potassium, (up to 12%) , but it is low in nitrogen and phosphate. It can contain in the region of 60 trace elements, growth hormones and other nutrients particularly rich in iodine and calcium. Spraying seaweed tea is said to increase resistance t…

Want to boost your soil? Get some seaweed

If you can afford only one type of fertiliser, Alys Fowler says, make it seaweed

‘In general, seaweeds contain 10 times the mineral levels of land-based plants.’ Photograph: Alamy

‘In general, seaweeds contain 10 times the mineral levels of land-based plants.’ Photograph: Alamy

Last modified on Fri 1 Dec 2017 15.42 GMT

I am always in awe of the fact that there is a garden under the sea; that plants can not only survive but thrive in a watery world that is turbulent and ever changing.

Seaweed is magical stuff in the water, and it’s somehow even more so when out of it. It’s incredibly healthful to us, to our animals, to our soils and our plants. It seems anyone who gets to ingest a little seaweed does better for it.

As seaweed breaks down into the soil, it encourages microorganisms whose activities help convert unavailable nutrients into forms that plants can use. It increases chlorophyll production and contains many micronutrients important for soil and plant health, as well as acting as a growth stimulant: it is rich in cytokinins, plant growth hormones that work above and below ground, improving root growth.

I recently went to Inagh Valley Trust, a seaweed research centre in Connemara, Ireland. They’re developing all sorts of interesting seaweed products, including adding seaweed to manufactured bread to increase its shelf life, and creating a seaweed feed for honeybees, to improve hive conditions and combat disease.

I spent a morning geeking out on seaweed spores swirling around in glass jars as they went through propagation, and munching on seaweed health bars. Then I went to the coast and wondered how much beach-strewn seaweed I could cram into my suitcase home – and whether Ryanair would complain about the smell.

It’s very important to collect only seaweed that has washed up; it’s not sustainable for everyone to go around the rocks pulling it off. Winter storms, however, often wash up great mountains of the stuff. There are brown, red and green algae, and all have different nutrient levels, so collect a variety, if you can. In general, seaweeds contain 10 times the mineral levels of land-based plants and are particularly rich in iodine and calcium. You can put them directly on beds; they will be salty, so you can’t plant direct into them, but a winter of rain will wash the excess salt away.

If you can afford only one type of fertiliser, Alys Fowler says, make it seaweed