SOURCES OF PLANT-FOOD 



acid by reason of the large amount of bone in the 

 mixture. Only a guarantee of analysis affords 

 safety to the buyer. It is a relatively slow and 

 good fertilizer, and is used usually in connection 

 with forms of plant-food that are more quickly 

 available. 



Fish. Near the Atlantic coast a large quantity 

 of ground fish, after the extraction of oil, is used 

 as a fertilizer, but the cost of the nitrogen and 

 phosphoric acid in this carrier is relatively too 

 high to justify its free use. Like dried blood, its 

 organic character gains for it a popularity that 

 does not have full justification in fact. 



Animal Bone. The original source of phos- 

 phoric acid as a fertilizer was animal bone, just 

 as hard- wood, unleached ashes were the source 

 of potash. The organic character of the animal 

 bone made it appear more truly a manure than 

 could any rock or other inorganic substance. 

 There is no more satisfactory source of phosphoric 

 acid than animal bone, and if it were in full supply 

 for the needs of soils, there would be little occasion 

 to discuss the merits of rock-phosphate and other 

 similar materials. The supply is a small fraction 

 of the need. If all animal bone were carefully 

 saved and returned to the land that produced all 



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