How may this devastation be arrested?
Is any soil inexhaustible?
What is usually the best source from which to obtain phosphoric acid?
The evident tendency of cultivation being to continue this murderous system, and to prey upon the vital strength of the country, it is necessary to take such measures as will arrest the outflow of this valuable material. This can never be fully accomplished until laws shall be made preventing the wastes of cities and towns. Such laws have existed for a long time in China, and have doubtlessly been the secret of the long subsistence and present prosperity of the millions of people inhabiting that country.
We have, nevertheless, a means of restoring to fertility many of our worn-out lands, and preserving our fertile fields from so rapid impoverishment as they are now suffering. Many suppose that soils which produce good crops, year after year, are inexhaustible, but time will prove to the contrary. They may possess a sufficiently large stock of phosphoric acid, and other constituents of plants, to last a long time, but when that stock becomes so reduced, that there is not enough left for the uses of full crops, the productive power of the soil will yearly decrease, until it becomes worthless. It may last a long time, a century, or even more, but as long as the system is—to remove every thing, and return nothing,—the fate of the most fertile soil is evident.
The source mentioned, from which to obtain phosphoric acid, is the bones of animals. These contain large quantities of phosphate of lime. They are the receptacles which collect nearly all of the phosphates in crops, which are fed to animals, and are not returned in their excrements. For the grain, etc., sent out of the country, there is no way to be repaid except by the importation of this material; but, all that is fed to animals, or to human beings, may, if a proper use be made of their excrement, and of their bones after death, be returned to the soil. With the treatment of animal excrements we are already familiar, and we will now turn our attention to the subject of
BONES.
Of what do dried bones consist?
What is the organic matter of bones?
The inorganic?