Excerpts from Jim Conrad's
Naturalist Newsletter

from the October 23, 2011Newsletter issued from Mayan Beach Garden Inn 20 kms north of Mahahual; Caribbean coastal beach and mangroves, ~N18.89°, ~W87.64°, Quintana Roo state, MÉXICO
GARDENING WITH SEAWEED
Each day brings a new crop of wind- and current-dumped seaweed onto our beaches. Some local property owners expect their live-in caretakers to keep their sand yards free of seaweed and everything else, so the daily gathering up this flotsam can be a major chore. Seeing the situation, recent visitor Lorna couldn't suppress her opinion that not using the seaweed was a waste. In Lorna's native Isle of Jersey, off the coast of Normandy, traditionally seaweed was collected and plowed into the soil to enrich it.

When Lorna returned home she sent me a link to a 1966 paper in the journal Agricultural History Review by Brian Blench, called "Seaweed and its Use in Jersey Agriculture," at http://www.bahs.org.uk/14n2a4.pdf.

Among several colorful eye-witness accounts, the paper quotes J. Poingdestre writing in 1682 after a visit to the islands. He reported that "every one of them (had) enough (seaweed) to lay it upon theire grounds as thick as ye spade or plough can turne and cover with conveniency."

Soon after my arrival here on our sand ridge I mixed sand and washed-up seaweed that had lain awhile to have the salt rained off it, and got a mixture in which seeds germinated and plants grew -- until Black Iguanas ate nearly every plant. The few remaining plants grew up stunted and yellowing, displaying classic signs of nutrient deficiency, especially nitrogen. Decomposed seaweed would have provided more available nutrients. I encouraged the staff to pee with me onto the compost heap, for urine has a lot of nitrogen in it, but somehow the practice didn't catch on. I think that urine and livestock manure added to seaweed and properly watered and aerated would compost into a fine, nitrogen-rich growing medium.

Lorna mentions making a nutrient-rich "tea" of seaweed soaked in buckets of water. On the Isle of Jersey, seaweed also was burned to produce potassium-rich ashes for use as fertilizer.

Lacking a good nitrogen source here, maybe our best use of washed-up seaweed would be as mulch during the dry season.

For years Marcia has fed kitchen scraps and seaweed to a certain spot which was never aerated, so that basically things rotted anaerobically. Parts of that pile eventually produced fine potting soil, though it crawls with tiny biting ants.