To produce cheap corn on poor land, one needs a clear understanding of what elements of the crop air and water will furnish, and what they cannot supply.  It should be remembered that the atmosphere is precisely the same over ground which yields 100 bushels of corn per acre, that it is over that which produces only five bushels per acre.  Now, the whole matter which forms the stems, leaves, roots, cobs, and seeds of corn, where the crop is 100 bushels per acre, is not part and parcel of the soil.  A harvest equal to fifty bushels per acre can be obtained without consuming over ten per cent, of earth, as compared with the weight of the crop.  No plant can imbibe more of the substance of the soil in which it grows, than is dissolved in water, or rendered gaseous by the decomposition of mould.

The quantity of matter dissolved, whether organic or inorganic, during the few weeks in which corn plants organise the bulk of their solids, is small.  From 93 to 97 parts in 100 of the dry matter, in a mature, perfect plant, including its seeds, cob, stems, leaves, and roots, are carbon (charcoal) and the elements of water.  It is not only an important, but an exceedingly instructive fact, that the most effective fertilisers known in agriculture are those that least abound in the elements of water and carbon.  The unleached dry excrements of dunghill fowls and pigeons, have five times the fertilising power on all cereal plants that the dry dung of a grass-fed cow has, although the latter has five times more carbon, oxygen, and hydrogen, per 100 pounds, than the former.  Although it is desirable to apply to the soil in which corn is to grow as much of organised carbon and water as one conveniently can, yet, where fertilisers have to be transported many miles; it is important to know that such of the measure as would form coal, if carefully burnt, can best be spared.  The same is true of those elements in manure which form vapor or water, when the fertiliser decomposes in the ground.

Carbonic acid and nascent hydrogen evolved in rotting stable manure are truly valuable food for plants, and perform important chemical offices in the soil; but they are, nevertheless, not so indispensable to the economical production of crops, as available nitrogen, potash, silica, magnesia, sulphur, and phosphorus.  These elements of plants being less abundant in nature, and quite indispensable in forming corn, cotton, and every other product of the soil, their artificial supply in guano, night soil, and other highly concentrated fertilisers, adds immensely to the harvest, through the aid of a small weight of matter.  In all sections where corn is worth 30 cents and over a bushel, great benefits may be realised by the skilful manufacture and use of poudrette.  This article is an inodorous compound of the most valuable constituents of human food and clothing.  It is the raw material of crops.

It is not necessary to restore to a cornfield all the matter removed in the crop to maintain its fertility.  A part of each seed, however, ought to be carried back and replaced in the soil, to make good its loss by the harvest.