l8 CELERY CULTURE 



guanos is in a very soluble state and is quickly 

 available. The nitrogen in sulphate of ammonia, 

 bone meal, and fresh stable manure acts more 

 slowly and its influence extends over a longer period. 



Sources of Phosphorus. — This element is not 

 found in nature except in combination ; calcium 

 phosphate is the usual form. The principal sources 

 of this phosphate are the phosphate rocks of South 

 Carolina, Florida and Tennessee, bones, guano, and 

 stable manure. If bones are ground very finely 

 they become soluble to a limited degree. Phos- 

 phate rock, however, as mined is very slowly avail- 

 able. It is therefore treated with sulphuric acid, 

 which converts part of the phosphate into a more 

 soluble form which for the most part is immedi- 

 ately available to plants. The untreated calcium 

 phosphate when ground very finely is sold under the 

 name of floats, in which form its application to the 

 soil gives a slow but lasting efifect. For celery pure 

 raw bone is perhaps the best form of calcium phos- 

 phate, but its availability depends largely upon how 

 finely it is ground. 



Sources of Potassium. — -This element is com- 

 monly found in the potash salts known as sulphate 

 of potash, muriate of potash, and kainit. Large 

 quantities of potash are also secured in the form 

 of wood-ashes. Stable manure contains a consider- 

 able amount. Most of the heavier soils contain 

 plenty of potash, but in a form that is slowly avail- 

 able for plants to feed upon. Humic, and light soils 

 generally, are deficient in potash owing to their 

 leaching qualities. Potash is one of the cheapest 



