BRIAN KIDD: Seaweed – the perfect manure for improving light, sandy soils

Seaweed - free from any public beach
Seaweed - free from any public beach
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Again, thank you for your letters. This week’s article is inspired by Sally who lives alongside the sea at Hayling Island where her soil dries out because it’s so sandy and the wind blows it on to the beach.

Sandy soil is easy to work. It warms quickly and is excellent for growing root vegetables. The problem is it dries too rapidly and nutrients in the soil often drain away in heavy rain.

The same conditions apply to city soils where the ground has been cultivated for many years. The soil becomes dark and light in texture. These black soils are gradually turning into silt.

Mother Nature can improve things and it’s a case of working with her over many years so the soil structure can be gradually improved.

For years good gardeners have used seaweed as a manure – it’s just what is needed to improve light soils.

Seaweed is full of jelly. If mixed with straw it does a great job improving light soils.

Imagine you’re in the kitchen and someone is making a jelly. Pinch a cube, pop it in your mouth and you can taste the flavour. As it dissolves, put a drinking straw in your mouth and slide it across your tongue. Now sprinkle some sand on a piece of paper, take the straw from your mouth and roll it in the sand. The sand sticks to the straw. This is what we’re going to do by adding straw and seaweed to the ground, making the sand bind the straw and seaweed.

Choose a freshly-dug area of soil and use either a compost bin, an old dustbin upside down or surround the area with boards ensuring there are no gaps between them and no holes in the sides. If you can’t do this, use a wire surround and, inside, peg old compost bags so moisture will be retained in the new heap.

On the soil, put a four-inch layer of straw. Strawy manure is fine. Then add an activator such as Garrota or sulphate of ammonia dissolved in water. This must be evenly sprinkled, not poured. Now add a four-inch layer of any kind of seaweed. You can gather this from any public beach. Add the activator again and a four-inch layer of straw. After every layer add the activator. This is essential.

Cover the top immediately with old carpet or polythene bags to retain the moisture, ammonia gas and heat.

Once the container is full, cover again after giving the heap a good soaking of the sulphate of ammonia, about a gallon to each square yard surface, sprinkled slowly. Now cover the top.

In two months you will have one of the finest mediums for sandy soil, just like peat. The great thing is that you will be able to fork it into the soil in spring.

Lightly work it into the top few inches or scatter it over the top of the ground.

What happens next?

This material will bind the sand together and absorb moisture and fertiliser elements from the soil and as the roots enter they will absorb what they need.


If you are thinking about cleaning the pond, do it before frogs and toads begin to spawn.

If they are already active, just remove sludge from the bottom of the pond, split water lilies and replant them in baskets.