RE:I had no weeds, and at harvest time, no digging to do, and the potatoes were large and blemish free. The seaweed prevented any weeds from growing before next planting.

it was common to use sea weeds as fertilizer, and salt hay (hay from grasses grown in salt marshes) as mulch in times past. many of them have seeds that will only germinate in brackish water, so they do not create weed problems they way letting a field go fallow, and be planted with rye grass or or grass the was plowed back into the earth would.

but vraic is a new word... is vraic {wrack} related to wrack and ruin? --(is this a YART? i dimmly recall some discussion of this--something about wrack and wreck some time ago...)