MANURES, LIME AND FERTILIZERS 69 



to its popularity. The availability of bone meal depends 

 primarily upon its state of division, the finest decom- 

 posing most rapidly. 



Sources of phosphoric acid. As previously stated, 

 ground bone is used extensively by florists and to some 

 extent by vegetable forcers. The phosphoric acid in 

 bone meal ranges from 20 to 30 per cent. There are two 

 classes, viz., raw bone and steamed bone. Raw bone 

 meal is coarser in texture, contains the natural fat and 

 decomposes slowly. Steamed bone meal has had the 

 fatty material removed by treating the bones with steam 

 under high pressure before they are ground. The 

 steamed bone meals and flours are of fine texture, and 

 for this reason and because of the absence of fats they 

 decompose and become available much more quickly 

 than the raw bones. 



Acid phosphate may also be used in greenhouse soils. 

 In this form, from 14 to 17 per cent of the phosphoric 

 acid is available. Floats, or the untreated ground rock, 

 might also be used to advantage in greenhouse soils 

 which are so heavily charged with organic matter. 



Thomas slag, which contains from 15 to 20 per cent of 

 phosphoric acid, should prove satisfactory in vegetable 

 forcing. 



Sources of potash. Of the various forms of potash, 

 muriate of potash is used most extensively for open 

 ground crops, and there is no evidence that it is not as 

 satisfactory as other potash materials for greenhouse 

 work. It contains about 50 per cent of actual potash. 

 Sulphate of potash, another product of the German 

 mines, contains about the same percentage of potash as 

 does muriate of potash, though the purer grades carry 

 larger amounts. Tobacco stems and wood ashes are 

 also available as sources of potash. 



