86 Effective Farming 



Phosphates from iron furnaces. In the manufacture of 

 steel from phosphatic iron ore, a slag results as a by-product 

 which contains phosphorus. This material when ground 

 makes a valuable fertilizer. It is called basic slag, also Thomas 

 slag. It contains about 8 per cent phosphorus in the tetra- 

 calcium form, which is more readily available than the tri- 

 calcium form in untreated bone or raw rock, and the fertilizer, 

 for this reason, is usually applied to the soil as powder without 

 treatment with sulfuric acid. The slag contains lime also which 

 is of value, especially if applied to acid soils. (See paragraph 

 43.) 



37. Potassic fertilizers. The chief potassic fertilizers are 

 salts taken from mines in Germany, wood-ashes, and certain 

 American products. The potash mines in Germany are located 

 at Stassfurt and the industry is an extensive one. During the 

 war with Germany these fertilizers are not available and a 

 relatively small quantity of potash can be procured. 



Salts from German mines. The chief fertilizers from the 

 mines in Germany are a crude salt known as kainit and two 

 refined salts, muriate of potash and sulfate of potash. Kainit 

 is about 12 per cent potash ; both of the refined salts contain 

 about 50 per cent potash. All of these fertilizers are soluble 

 in water and are used without treatment. 



Wood-ashes. If they can be secured unleached,. wood-ashes 

 are valuable for the potash and phosphorus they contain. 

 Formerly they were more plentiful than at present. Unleached 

 ashes contain about 5 per cent of potassium and 5 per cent of 

 phosphorus. 



American potash. With no potash available from Germany, 

 it became necessary to develop the potash resources of this 

 country. As a result of investigations by the Government and 

 the fertilizer companies, several sources have been developed 

 and much of the product placed on the market. Among the 

 materials used are ground kelp, charred kelp, Great Salt Lake 

 potash, and Searles Lake potash, which furnish the plant-food 



