130 



Food for Nitrogen of organic matter and ammonia salts. It is due 

 to the action of microscopic organisms, and all Nitrogenous 

 manures undergo this process before plants use it. 



Phosphoric acid, one of the essential fertilizing ingre- 

 dients, is derived from materials called phosphates. It does 

 not exist alone, but in combination, most commonly as 

 phosphate of lime in the form of bones, rock phosphate, 

 and phosphatic slag. Phosphoric acid occurs in fertilizers 

 in three forms— soluble, reverted, and insoluble phosphoric 

 acid. 



Superphosphate. — In natural or untreated phosphates 

 the phosphoric acid is insoluble in water and not readily 

 available to plants. Superphosphate is prepared from these 

 by grinding and treating with sulphuric acid, which makes 

 the phosphoric acid more available. Superphosphates are 

 sometimes called acid-phosphates. 



Potash, as a constituent of fertilizers, exists in a num- 

 ber of forms, but chiefly as sulphate and muriate. All 

 forms are believed to be nearly, if not quite, equally 

 available. The chief sources of potash are the potash 

 salts from Germany — kainit, sylvinit, muriate of potash, 

 sulphate of potash and magnesia. Canada wood ashes and 

 cotton-hull ashes are also sources of potash. 



Ammoniates. 



Per cent 

 ammonia. 



Nitrate of Soda 19 



Dried blood 14-5 



Tankage '3-3 



Dry fish scrap . 10 



Cotton seed meal 8.5 



Barnyard manure 0.6 



Phosphates. 



Per cent Lbs. Phosphoric 



phosphoric acid. Acid per ton. 



Superphosphate 15 300 



Ground bone 22 440 



Bone tankage 12 240 



Thomas slag 16 320 



Barnyard manure 0.32 6.40 



