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Kelvin Passfield: Seaweed is a good local fertiliser

Saturday 23 May 2020 | Written by Losirene Lacanivalu | Published in Environment


Kelvin Passfield: Seaweed is a good local fertiliser
Tehahawai Passfield. 3, with turbinaria seaweed. 20052233

OPINION: Fertilise your organic vegetables and help clean up the coastline at the same time.

This week, Te Ipukarea Society staff joined the Ministry of Marine Resources to assist with a seaweed survey around the island of Rarotonga.

This provided us an opportunity to see what some of our most common seaweeds were currently in our lagoon.

It also provided an avenue to continue our line of articles in recent weeks based around home gardening as a useful way to get through a pandemic. So today we are discussing using seaweed as a natural organic tonic for your plants.

Seaweed is known as one of the best soil conditioners because it contains so many trace nutrients.Seaweeds also contain nitrogen in the ionic form, which is more readily absorbed by the plants.

Most people will recall about four years ago we had an excess of seaweed being produced in our lagoon, especially in Muri.

This was a real problem for tourism accommodations in the area, as well as being very unpleasant for tourists. The main culprit at that time was a type of Caulerpa seaweed. Caulerpa is still very abundant in Muri, and remains present all around the island.

Another very common seaweed in our lagoon is Turbinaria. In India they use this seaweed as a fertiliser for farming. It contains the elements nitrogen, phosphorous and potassium, which are all components of the commercial NPK fertiliser you buy from the store, though in much lower concentrations. It also has many other trace minerals that your plants will love.

You can use the seaweed that washes up on the beach directly on to your garden as a mulch. If you are concerned about the salt content of the seaweed, just spread it out and hose it down or leave it to rinse in the rain before putting it around your plants.

However, because it is slightly alkaline, it is not recommended for some plants that like a lot of acid such as strawberries.

You can also make a liquid tonic for your garden by soaking the seaweed in a container of freshwater with a loose-fitting lid for six to eight weeks.

You can put the seaweed into an old onion sack first, so you can later squeeze it out like a giant tea bag! Best to do this away from your house, as it can generate quite the unpleasant smell.

Also, make sure there are no gaps where mosquitoes may get in to breed.

This solution will contain all the trace elements and nutrients released from it. It is quite concentrated, so only add about 500mls to a full bucket of water and pour this around your plants. You can also spray it on the leaves.

If you like the idea of using locally-produced organic fertiliser, but don’t want to go to the trouble and inconvenience of making your own, there is an alternative.

Dennyfield (soon to rebrand as Southside Organic) are selling fish emulsion fertiliser at Aquaflow in Tupapa, CITC Building Centre in Avatiu, and Vonnia’s Yard Stop in Arorangi. They will soon also have a seaweed emulsion in production.

So go local and healthy by growing your own organic vegetables fed by your own locally made fertiliser!