74 SUCCESSFUL FARMING 



extent gathered from different parts of the world, and are either treated 

 to increase availability or combined into mixed fertilizers before being 

 offered to the farmer. Fortunately the fertilizing element most needed 

 in the soils of the United States and Canada, namely, phosphorus, is 

 secured chiefly from extensive deposits of phosphate rock in Florida, 

 South Carolina and Tennessee and a few other states. This supply is 

 supplemented to some extent by bone phosphate, which comes chiefly 

 from the slaughter-houses of the country; also by basic slag, a by- 

 product of steel manufacture. 



The potash salts are secured almost exclusively from the extensive 

 potash mines in Germany. Potash salts come to us in different forms. 

 Most of them have been manipulated and more or less purified. The 

 one most extensively used is known as muriate of potash and is a chloride 

 of potassium (KC1). Sulphate of potash and carbonate of potash are 

 used to a somewhat less extent. In addition to these we have some of the 

 crude potash salts, such as kainite and manure salt. A comparatively 

 new source of potash suitable for commercial fertilizers has been found in 

 the extensive kelp groves in the Pacific Ocean off the coast of the United 

 States and Canada. As yet these have not been extensively used as a 

 commercial source of potash. 



Nitrogen is available chiefly in the form of nitrate of soda, which 

 comes from Chile. We also have sulphate of ammonia, an extensive by- 

 product from coke ovens and from the manufacture of artificial gas. As 

 yet the nitrogen escaping from coke ovens is not all transformed into 

 sulphate of ammonia. There are also organic forms of nitrogen, chief of 

 which are cottonseed meal, dried blood, tankage, fish scrap, guano, castor 

 pomace, together with small amounts of horn, hair, feathers and wool 

 waste. 



Carriers of Nitrogen.— Nitrate of soda (NaN0 3 ) contains 15 per 

 cent of nitrogen. It is readily soluble in water, and nitrogen in this form 

 is immediately available for plants. It should be applied in small quan- 

 tities and not long prior to the time plants most need their nitrogen supply. 



Sulphate of ammonia (NH 4 ) 2 S0. 1 contains 20 per cent of nitrogen. 

 Like nitrate of soda, it is quick acting, but for most crops the ammonia 

 must first be converted into the nitrate form before it can be utilized. 

 Some crops, however, can utilize ammonia as such. Sulphate of ammonia 

 is not leached from the soil quite as rapidly as nitrate of soda, but never- 

 theless it should not be applied in larger amounts than are necessary, 

 nor far in advance of the needs of the crop. 



Cottonseed meal is another source of nitrogen which is extensively 

 resorted to in the cotton belt. It contains from 3 to 8 per cent of nitrogen, 

 with an average of about 6.8 per cent. It is not wholly a nitrogenous 

 fertilizer, since it also contains an average of 2.9 per cent phosphoric 

 acid and 1.8 per cent potash. The nitrogen in cottonseed meal being in 

 an organic form, is rather slowly available. Availability is gradually 



