BONES AS MANURE. The employment of hones as a manure is one of the greatest modern improvements in agriculture. They are applied either simply reduced to small fragments or a coarse powder called bone dust (q.v.), or. after undergoing chemical preparations of various kinds, as the basis of highly valuable artificial manures.—See BONE-ASH, and BONES, DISSOLVED.—All the substances which enter into the composition of bones are desirable additions to the soil, but particularly the phosphates. Phosphoric acid, usually found in combination with magnesia. and more particularly lime, enters into the structure of every plant and animal; it is a substance, therefore, which cannot be dispensed with either in the vegetable or animal economy. Being very sparingly diffused through most soils, it is often essential to add it artificially. The productive ness in many districts of Britain had become much impaired by the diminution of phosphoric acid in the soil, owing to the quantity taken off in corn, cheese, and the B. of animals, which were annually raised and exported. The fine red sandstone learns of Cheshire were comparatively sterile in the end of the last century, which was entirely owing to the deficiency of phosphoric acid in the soil, no doubt partly to be attributed to the quantity yearly abstracted by the dairy produce sent to market. So _much was this the case, that a liberal dressing of common or calcined B. had the effect of at once doubling the value of the worn-out pastures. Iu other parts of Britain, however, such as the clay-soils of Suffolk—wbich at one time were under dairv-farms—the Pon is rich in phosphates, and the application of B. as a manure is there attended with little effect.
It becomes, therefore, of practical impw-tEnce to ascertain when this substance slicul,1 be added, and when it is not necessrry ti) do so. It is important to observe, that although phosphoric acid is as essential to one crop ns to another, yet fOnle crops, such as turnips, require a far more liberal or';figiat supply of it than others, or wheat. which :actually require as much to build up their structure. We will shortly state the prin ciples which should regulate the practice of bone-manuring.
All perennial Plants, such as grasses, are enabled to extract phosphoric acid from the soil more rembly than annual plaits, owing to their numerous and well-developed roots, which are ready,. even at the beginning of the growing season, to draw supplies from a large muss of soil. Grasses, therefore, are only benefited by phosphoric manures whit n the soil is more than usually deficient in phosphates. If grass-lands arc sterile, it is easy to ascertain if a deficiency of phosphoric acid is the cause, by adding calcined or crushed B., and watching their effect. An experiment of this sort is a intieh better guide than any analysis of the soil In Cheshire, the quantity of 13. applied to the i pastures is from half it ton to a ton per acre; and this dressing will last from 16 to 25 years.
Wheat, also, from the long time it occupies the ground before it Is ready to be reaped, and its slow growth during its early singes, MR thrive with a small supply of phosphates. These substances are, therefore, comparatively seldom applied directly Lisa manure for this crop. So, alai), with carly-sown oats or barley. When thee latter crops, however, are late sown, and the rapidly growing conditions of heat and moisture exist, phosphates are often applied with great benefit.
It is as an application to the turnip that phosphoric acid is so marked in its effects, even when the soil already contains.:,. in considerable quantity. The reason of this is not difficult to trace. The seed of the turnip is small, and it is sown at the warm st riot, wilco' the growth is rapid. The seeds themselves have only a limited quantity of phos phates stored up for the benefit of the roots and leaves of the young plants.
the roots, therefore, while yet short, meet with a concentrated supply, the other elements of the food of the plant—carbonic acid, water, and ammonia—however abundantly they may be present, cannot be assimilated, and its growth is arrested. Besides, a liberal supply of phosphates has the effect of pushing on the turnip -threw :11 its early stages, when it is so liable to injury from various insects.
The effects of B. as a manure for the turnip are greatly increased by dissolving them in sulphuric acid, and manufacturing the soluble superphosphate of lime. sug gested such a Ilse of sulphuric acid in and since then, hundreds of manofactories of this manure have arisen over the land. The utility of the discovery, however, is cot at present so great as is sometimes represented, owing to the large supply of rhosphatie guanos now in the market. In these the pho.Thate of lime is in a finely divided state, and is readily enough taken up by plants without being dissolved by acids. No doubt, as the scarcity of guano begins to be experienced, and its price rises, it will again become a lunch greater object than at present to manufacture superphosphate from mineral phos phates or hones. Three to four cwts. of dissolved B. or of phosphatic guano is the quau tity usually applied to an acre of turnips.
The vatue of B. as a manure has been long known in some parts of England, hot their use was merely local, until more than two decades of the 110 e. had passed; aril they were merely broken by a hammer, or rudely or imperfectly crashed by being laid in rats where cart-wheels might pass over them. The first machines for brne-cntshing were employed in Yorkshire and Lincolnshire in 1814 or 1815, and reduced them only to pieces about the size of n walnut, much larger than the coarsest or "rough" hone dust: now in use. The employment of this manure did not become general in Scotland till about 1830, although it had been introduced in East Lothian some years before. It.; use has now extended to different parts of the continent of Europe and to North Ame rica.