The condition of clay soils is also permanently improved by mixing a due proportion of sand in them. The most durable and perfect soil is chiefly composed of certain proportions of sand, clay, lime, and vegetable matter in a state of decomposition, and, whenever any soil is destitute of a due proportion of any of these, the addition of such earthy substance can never fail to serve as a manure.
The stony earth called Pyrites, when pulverised by the aid of a proper degree of calcination, is much used; and highly esteemed in Flanders as a top dressing for grass lands, as is mentioned in a communication of the late Chancellor Livingston to the Society for the promotion of the useful arts in this state. We will refer the reader to the 2d vol. published by that Society for the manner of preparing this manure, and the quantity to be used, &c.
Of coal, we shall merely state that, from the results of experiments made by the late Mr. Muhlenburg, (of Penn.) about 40 bushels to the acre of this substance, pulverised in the manner of gypsum, was found a good manure, when applied as a top dressing.
Common salt, pulverised, and applied as a top dressing, at the rate of from two to four bushels to the acre, has, in many instances, powerful effects as a manure. Sea-water is peculiarly adapted for this purpose. Mr. Deane, in his Farmer's Dictionary, mentions an instance where a crop of potatoes, and another of flax, were greatly increased in product by an application of sea-water to them while growing. About a pint of the water was applied to each hill of potatoes, and for the flax crop the water was sprinkled over the ground.
Some trials have been made in this country of using burnt clay as a manure, and its use is recommended, particularly for all dry arable lands, not inclining to clay. The first step in preparation for burning clay, is to have a considerable quantity of this earth dug up in spits, and laid to dry in the sun: when pretty well dried you prepare for burning by raising a little pile of dry wood in the shape of a pyramid, say 4 or 5 feet high;--round this you build up the dried spits of clay, leaving a hole at the bottom, for the entrance of the air, and another at the top for it to pass off. Such, at least, was the method formerly practised in Great Britain, but the modern improvement of retaining the smoke within the mass, agreeably to the plan spoken of by Mr. Cobbett, for burning earth, ought also to be pursued in burning clay. After the fire has been set to the wood you continue digging up fresh clay and piling it around and over the heap, as fast as the fire penetrates the mass, taking care, however, not to pile on so much at once as to extinguish the fire. If there be danger of its becoming extinguished, it may be advisable to make one or more holes in the sides of the heap by running a hole into it. The fresh earth is to be added during pleasure or until a sufficient quantity is burned. After the heap has cooled it is fit for use, either by mixing with the soil as directed by Mr. Cobbett, for applying burnt earth, of which we will next speak.