When Welsh farmers were reliant on the humble seaweed for fertiliser

While exploring parts of the Welsh coast we began to wonder about the man-made ramps seen on cliff slopes. Even when partly concealed by scrub, they are surprisingly frequent.

What, we wondered, might have been of sufficient value to warrant the labour of making routes to shores for pack animals, or even carts?

Beyond the transport of goods by sea, or to get to places suitable for launching fishing boats, there must have been other reasons for improving access to the shore.

Pre-industrial accounts from all Welsh coastal counties, from Glamorgan to Denbigh, make frequent reference to seaweed as “manure”.

The term “‘manure”, before artificial fertilisers were available, covered much more than just farmyard muck. Seaweed was usually spread on the land and then ploughed in, though sometimes it was composted.

It was often collected in large quantities after being washed up by storms. A striking, but perhaps exaggerated account, records that as many as 2,000 cart loads of seaweed were cast up by a storm near New Quay, all of which were carried away by farmers in a fortnight.

Elsewhere there is a claim that for 70 years “undiminished” crops of barley were taken from a field manured with seaweed.

A letter in the Anglesey Archives tells of two men drowning in 1843 when the boat they were using to collect seaweed for potato manure capsized.

Roman writers mentioned the use of seaweed as manure and in Wales there is some documentary evidence of it at least back to Tudor times.

Seaweed may have continued to be used on a limited scale long after artificial fertilisers became available.

Often they contain high amounts of potash, particularly oarweeds or kelps. When the German source of potash fertiliser ceased during WWI, there was renewed interest and a flurry of scientific studies, which showed that some constituents of seaweed were also acting as conditioners in clay soils.

Memory of seaweed use on coastal farms still persists. Bryn Jones, National Trust countryside manager in Anglesey, said it was added to farmyard manure heaps in alternating layers.

Some was even was fed to livestock: indeed, in a few places where cattle have access to the shore, they can still be seen eating freshly stranded kelp.

The enhancement of farmland productivity in coastal districts by using marine manures is likely to have been a long established practice.

At the same time the sea was a major highway for trade and in a few places the sea even provided the power to grind corn.

It is tempting to suggest that Anglesey’s reputation as Môn Mam Cymru may have rested in part on fertility derived from the sea.

Co-authors Ivor and Jane Rees have a long standing interest in the natural histories of Anglesey.

 

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