562 Agricultural Chemistry — Turnips. 



alkalies ; while the wheat removes about 12 lbs. of potash and 30 

 lbs. of phosphates. We see, therefore, that much of the organic 

 matter of the turnip is lost to the farm by respiration, the 

 phosphate of lime largely in the formation of bone ; while the 

 export of potash is so small that the quantity contained in one acre 

 of turnips would not be entirely exported under twenty years. It 

 is clear, then, that unless by actual waste, there is, under an ordi- 

 nary course of farming, without the use of imported food, a com- 

 paratively small decrease in the amount of available alkalies in 

 the soil ; but when we consider the vast amount of alkalies existing 

 in the soil itself, and set free by annual decomposition, and that 

 in every well-cultivated farm there will be a considerable quantity 

 imported in cattle food, there can be little doubt that, under or- 

 dinary circumstances, the alkalies accumulate in the soil. It may 

 be further remarked, that in our experiments the alkalies, in 

 whatever form we applied them, were always injurious to the 

 vigorous growth of the young plant. Although the export of 

 phosphate of lime from a farm is very much larger than that of 

 the alkalies, the continual use of it as a manure for the turnip-crop 

 could not be advocated upon the ground of mere exhaustion ; for 

 it could be proved that where the supply of it to the turnip-crop 

 during successive years has been much greater than what has been 

 removed in produce, the effects of further applications were equally 

 successful. 



We are therefore inclined to limit the economical application 

 of mineral manures to phosphate of lime alone, and even then in 

 most cases it is employed not as an element of which the soil is 

 deficient, but as an agent for promoting to a remarkable degree 

 the early and vigorous development of the young plant, and car- 

 rying it with rapidity over those stages, any delay in which is at- 

 tended with great injury, and often with the destruction of the 

 whole crop. The sources of phosphate of lime are guano, bones^ 

 and the compound of bones and sulphuric acid, called super- 

 phosphate of lime. The latter manure is the form which is found 

 to produce the greatest effect upon the young plant, and espe- 

 cially upon the development of a large amount of fibrous roots. 

 Although strongly acid, it may be drilled with the seed without 

 the slightest injury to it. It must, however, be clearly under- 

 stood that the bulk of an agricultural crop of turnips depends 

 materially upon the amount of organic matter contained in the 

 soil, without which the development of the power of growth by 

 means of the phosphate wdll be unavailing. The first application 

 of a mineral phosphate is liable to produce heavier crops of tur- 

 nips than those which follow, unless the carbonaceous matter 

 taken from the soil by the turnips, and lost by the respiration of 

 the stock consuming them, has been made up by imported cattle 

 food. Rape-cake, as containing a large amount of organic matter. 



