Page:Encyclopædia Britannica, Ninth Edition, v. 1.djvu/379

Rh MANURES.] AGRICULTURE 353 commended as one of the most powerful of all manures for carrots. In London Labour and the London Poor we find the following statistics as to metropolitan soot : Bush, of Soot per annum. &quot; 53,840 houses, at a yearly rental above 50, producing six bushels of soot each per annum. . . 323,040 90,002 houses, at a yearly rental above 30 and below 50, producing five bushels of soot each per annum 450,010 163,880 house;), at a yearly rental below 30, producing two bushels of soot each per annum . . . 327,760 Total number of bushels of soot annually pro duced throughout London 1,100,810 The price of soot per bushel is but 5d., and sometimes 4^d., but 5d. may be taken as an average. Now, 1,000,000 bushels of soot at 5d. will be found to yield 20,833, 6s. 8d. per annum.&quot; 1 Section 19. Salt. Common salt has often been commended as a valuable manure, but has never been used in this way with such uni form success as to induce a general recourse to it. We have already spoken of it as forming a useful compound with lime and earth. It can also be used beneficially for the destruction of slugs, for which purpose it must be sown over the surface, at the rate of four or Jive bushels per acre, early in the morning, or on mild, moist days, when they are Been to be abroad. It is used also to destroy grubs and wireworm, for which purpose it is sown in considerable quantity on grass land some time before it is ploughed up. It can be used safely on light soils, but when clay pre dominates, it causes a hurtful wetness, and subsequent incrustation of the surface. Its application in its unmixed state as a manure is at best of doubtful benefit; but in combination with lime, soot, nitrate of soda, and perhaps also superphosphate of lime, it appears to exert a beneficial influence. Section 20. Nitrate of Soda. Cubic saltpetre, or nitrate of soda, has now become one of our staple manures. The fertilising power of common saltpetre 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 state, but contains a mixture of several sub stances, 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 per centage of nitrogen (the element to which the fertilising power of all manures is mainly due), it may seem sur prising 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 in spring, the former frequently yields a better profit than the latter ; and hence the importance to farmers of getting it at a more reason able 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 ft per acre, in combination with 2 cwt. of salt. The nitre and salt are thoroughly mixed, and carefully sown, 1 Farmers Magazine for March 1852, p. 254. 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 2 informs us that an application of 42 ft of nitrate of soda and 84 B) 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, profit able. 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. Section 21. Potash. Crude potash, or kainite, has of recent years been largely imported from Germany, and has been somewhat exten sively used in combination with other manures for potatoes and other root crops two cwt. per acre being a common rate for the potash. Section 22. Artificial Manures. Besides those 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, sul phuric 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 pre parations 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 recom mend those who desire information regarding the pre paration 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 Agri cultural Society of Scotland ; and the articles relating to Agricultural Chemistry in Morton s Cyc^cedia. Those who purchase manures of this kind ought to be very care ful 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. 2 Journal of Royal Agricultural Society, vol. xiii. p. 349. I. - 45