The Farmer's Assistant, p. 23-24 (1817)
John Nicholson

BURN-BAKING. A method of manuring stiff clay lands. It is performed by paring off the sward, in pieces about eighteen inches long, a foot wide, and two or three inches thick; these are set on their edges, leaning against each other, to dry, which in good weather requires about three weeks. They are then laid up somewhat in form of ovens, with their mouths to a common windward side, having a hole in the top of each for the smoke to pass off. In a dry day, when the wind blows into the mouths, they are set on fire with straw, and if they burn too briskly some earth must be thrown on to deaden the fires. At the end of about three days they will be completely burnt through, and then the burnt earth is spread over the ground and ploughed in with a shoal furrow.

For cuting up the swards in squares for burn-baking—a roller with sharp iron rims round it, at suitable distances, is to be used. As the roller passes over the ground the rims sink into it sufficiently deep. The ground is first to be cut one way with this implement; then with another implement, resembling a wheel plough; it is cut into squares, by crossing the direction of the roller, and the squares are at the same time severed underneath by a broad thin share for the purpose, and are turned over in the manner of turning over sward ground. They are then to be set up, as before directed.

Mr. Young, the late famous Agriculturalist, of Great-Britain, recommends burn-baking, where it can be easily performed, as highly beneficial to cold, stiff, and clayey soils.

BURNT CLAY. This is a good manure for clay and other heavy soils. In "The Complete Grazier," it is also recommended for light soils. The method of preparing it is as follows:

In the first place, dig your clay in spits of the size of bricks, and let them be well dried in the sun: Take small billets of wood, or faggots of brush, and pile them up in the form of a sugar-loaf three or four feet high; then pile your spits of dried clay closely round this, leaving a hole on one side to kindle the fire and another in the top for the smoke to pass off: Surround the pile again with two more enclosures of the spits of clay, and then kindle the fire. When it has gotten well on fire stop up the holes with clay, and the innate heat will so fire the mass, that wet clay may be thrown on in great quantities. Care must however be taken, not to lay it on so fast, nor so closely, as to put out the fire, as in that case you must begin anew. By raising a stage round the pile you may throw on clay till you get it as high as you please. The pile must be watched day and night, till fully burnt.

Farmers possessing clay lands will do well to make experiments of this manure. From ten to twenty loads of it is a suitable dressing for an acre.