X. MANURES (cont.)
Nitrate of Soda. Potash. Artificial Manures.
Nitrate of Soda
Cubic saltpeter, or nitrate of soda, has now become one of our staple manures. The fertilizing power of common saltpeter or nitrate of potass has been known from the earliest times, but its high price has hitherto hindered its use as a manure, except in the form in which it is obtained as refuse from the gunpowder mills. The cubic nitre is brought from Peru, where there are inexhaustible supplies of it. The principal deposits of nitrate of soda are in the plain of Tamarugal, at a distance of 18 miles from the coast. The beds are sometimes 7 or 8 feet in thickness, and from these it is quarried with ease. It is not found in a perfectly pure taste, but contains a mixture of several substances, chiefly common salt. To fit it for certain uses in the arts, it is subjected to a process of purification by boiling and evaporation. But for its use as a manure this is altogether unnecessary, and the cost would be greatly lessened if the nitrate were imported as quarried. As cubic nitre and guano contain very nearly the same percentage of nitrogen (the element to which the fertilizing power of all manures is mainly due), it may seem surprising that the former should ever be used in preference to the latter. In practice, however, it is found that when applied as a top-dressing on spring, the former frequently yields a better profit than the latter; and hence the importance to farmers of getting it at a more reasonable price. Nitrate of soda is used as a manure for grain and forage crops. It is now extensively used as a top-dressing for wheat. For this purpose it is applied at the rate of 84 lb per acre, in combination with 2cwt. of salt. The nitre and salt are thoroughly mixed, and carefully sown, by hand, in two or three equal portions, at intervals of several weeks, beginning early in March, and finishing by the third week in April. If nitre alone is used, it has a tendency to produce over-luxuriance, and to render the crop liable to lodging and mildew. But the salt is found to correct this over luxuriance, and a profitable increase of grain is thus obtained. Mr. Pusey [Footnote 353-1] informs us that an application of 42lb of nitrate of soda and 84 lb of salt per acre, applied by him to ten acres of barley that had been injured by frost, had such an effect upon the crop, that he had seven bushels more grain per acre, and of better quality, than on part that was left undressed for comparison. These seven bushels per acre were attained by an outlay of 6s. 4d. only. This nitre is also applied with advantage to forage crops. Mr. Hope, Fenton Barns, East Lothian, states that he finds the use of it as a top-dressing to clover, at the rate of one-cwt. of nitrate and two of guano per acre, profitable. Its beneficial effects are most apparent when it is applied to light and sterile soils, or to such as have been exhausted by excessive cropping.
Crude potash, or kainite, has of recent years been largely imported from Germany, and has been somewhat extensively used in combination with other manures for potatoes and other root crops --- two cwt. per acre being a common rate for the potash.
Besides this substances, the most important of which we have now enumerated, which are available as manure in their natural state, there are various chemical products, such as salts of ammonia, potash, and soda, copperas, sulphuric and muriatic acid, &c., which, in combination with lime, guano, night-soil, and other substances, are employed in the preparation of manures, with a special view to the requirements of particular crops. In some cases these preparations have been eminently successful, in others but doubtfully so. Many failures are probably due to the spuriousness of the article made use of; as it is known that enormous quantities of worthless rubbish have, of late years, been sold to farmers, under high sounding names, and at high prices, as special manures. We would recommend those who desire information regarding the preparation and use of such compounds to study the article on Agricultural Chemistry, by Mr. Lawes of Rothamstead, in the Journal of the Royal Agricultural Society of England (vol. viii. p. 226); the accounts of experiments with special manures in the Transactions of the Highland and Agricultural Society of Scotland; and the articles relating to Agricultural Chemistry in Mortons Cyclopedia. Those who purchase manures of this kind ought to be very careful to insist in every instance upon the seller producing an analysis by some chemist of established character, and granting a written warranty that the article sold to them is at least equal to the value indicated by the analysis. Were all farmers to insist upon this mode of buying their manures, they would at once put an end to that wholesale system of fraud by which they have been so enormously cheated of late years.
In applying these concentrated manures, those only of a slowly operating character should be used in autumn or winter, and at that season should invariably be mixed with the soil. Those in which ammonia abounds should in spring also be mixed with the soil when crops to which they are applied are sown. When used for top-dressing growing crops they should be applied only in wet weather.
353-1 Journal of Royal Agricultural Society, vol. xiii, p. 349.
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