Sea-Sludge, or Salt-clod, is the surface, or that part of a saline marsh, which is deposited by the high tides. It is much richer, and less intermixed with sand, than the land which is more regularly overflowed.
Sea-sludge is an excellent ma-nure; and though it be attainable only in a few situations, yet it deserves to be more generally employed. The best sludge is completely covered with grass: it is cut out of the marshes, to the depth of a spade, and, during the summer, is carted upon the land; on the surface of which it is spread, and suffered to remain in small clods, till it has become thoroughly mellowed by the winter frosts. It is then pulverized, by passing a harrow over the soil, after which it is ploughed-in with a thin furrow, for spring corn.
The proportion of this manure necessary for an acre, varies in different places, according to the nature of the ground; but, in general, it will be advisable to spread as much as will form a coat, or stratum, about an inch and a half or two inches in thickness. In some parts of Lancashire and Cheshire, sea-sludge is occasionally employed as a substitute for marle, to which it is greatly superior, both on account of its ameliorating properties, and the longer duration of its effects; instances having occurred, in which land, manured with such mire to the depth of two inches, has retained its fertility thirty years.