« AnteriorContinuar »
possessors by their fertility, while they have exposed those who succeeded them to immense expense and numberless failures; and this, through the sterility which abuse and mismanagement entailed upon them. Liebig has quoted the case of Virginia, where "harvests of wheat and tobacco were obtained for a century from one and the same field without the aid of manure; but now whole districts are abandoned and converted into unfruitful pasture-land, which, without manure, produces neither wheat nor tobacco. From every acre of this land there were removed in the space of 100 years 12,000 pounds weight of alkalies, in leaves, grain, and straw; it became unfruitful, therefore, because it was deprived of every particle of alkalies fit for assimilation, and because that which was rendered soluble again in the space of one year was not sufficient to satisfy the demands of the plants." What in this respect came under the writer's personal observation, illustrates still farther the facts stated by Liebig: several of the principal farms both in Virginia and Maryland, where the cultivation is similar,—as, for instance, those belonging to Mr. Charles Caroll of Carollton, to Messrs. Caton, Harper, Oliver, Taloe, &c, — had been a continuous source of ruinous expenditure and disappointment to their proprietors; and this for years, before they were brought to yield a tolerably good crop of wheat. Mistaken notions respecting the principles of the physiology of plants, and the agency of earths and alkalies in the process of nutrition, rendered that expenditure tenfold the amount which in the present day, with the assistance of "chemistry as applied to agriculture" would have been required to restore the productive power.
South America too, as well as North, presents several provinces, as the Sierra de Cordova, St. Juan de Ariqja and the Maypu of Chili, where the richest soils of former times now yield nothing unless they are irrigated; which again, though furnishing alimentary substances to crops of wheat, must, through the process of a fresh and continuous disintegration of earthy salts and alkalies, end in draining completely the soil from such ingredients, and in rendering it fit only for a vegetation which lives on silica and carbon.
In New South Wales the effects of exhaustion of soils begin to be felt also, and in Van Diemen's Land similar examples are not wanting. The soils No. 36 and 37, of the farms of Mr. Jamieson, of Glenlee, which in the course of eighteen years of cropping, without manure, have lost half of their productive power, offer one of the most striking examples.
"A soil," says Liebig, "will naturally reach its point of exhaustion sooner, the less rich it is in the mineral ingredients necessary as food for plants; but it is obvious that we can restore the soil to its original state of fertility, by bringing it back to its formercomposition, that is, by returning to it the constituents removed by the various crops of plants."
Again, "the principal object of agriculture is to restore to our land the substances removed from it, and which the atmosphere does not give, in whatever way the restoration can be most conveniently effected. If the restoration be imperfect, the fertility of our fields or of the whole country will be impaired; but, if, on the contrary, we add more than we take away, the fertility will be increased."
The restitution, then, to the soil of what is subtracted from it by cropping, becomes the imperative and sacred duty of every farmer: to withhold it, with a knowledge of the injury thus inflicted on the soil, and entailed upon its next possessors, borders upon a crime against society: at any rate it becomes a most flagrant abuse of the gifts of nature.
Now, in order that such restitution may be accomplished systematically and with economy of time and money, there is required in Australia, as elsewhere, a previous knowledge respecting —
First, The constituents of the plants which are to be produced, by which knowledge we obtain an evidence of the kind of food that each plant requires from the soil.
Secondly, Respecting the physical and chemical character of the soil which is intended to produce these plants, by which we ascertain the store of provision it contains to meet the demands which will be made upon it.
Thirdly, Respecting the constituents or the chemical nature of the manures, by which we may be enabled in case of need to heighten the energies of the soil, and to apply the remedy with a knowledge of what we are doing, and consequently with success.
The published analyses of the ashes of different plants, and of the greatest number of manures, by Liebig, Boussingault, Dumas, and other chemists, who in their most praiseworthy devotion to the public good and to science, have not shrunk from all the disgusting contact and painful exercise of patience which such analyses imply and require, furnish most ample information on the first and the last of the above points of knowledge essential to the farmer.
On the second point, which relates to the analysis of soils, knowledge cannot be arrived at except through the assistance of an analytical chemist: but, although more difficult to obtain, it deserves, on account of the range of its usefulness, the most serious attention of the Australian farmer.
It is high time, indeed, when the progress of civilisation is becoming like the rise of a tide, which drowns those who do not keep pace with its flow, that the farmer, to whom science is ready to offer her services, should emancipate himself from the old hackneyed custom, under which he committed seeds to soils indiscriminately, and, in case of failure, applied remedies in total disregard and utter ignorance of the seat or cause of the evil; remedies, which, like the panaceas of a quack treatment, were experiments, but not improvements.
The knowledge of the three above pointed out requisites will lead the farmer to adapt either the plant and the manure to the soil, or the soil and manure to the plant, with equal success; and, in either case, without risk of time or money.
As a practical illustration of these rules: —Amongst the reviewed soils, and not included in the Table I. and II., are the soils No. 20, No. 25, and No. 29, of which the physical and chemical character is as follows: —