CROPS AND SOIL IMPROVEMENT 



nearly as much nitrogen as nitrate of soda, run- 

 ning from 13 to 15 per cent. The nitrogen is not 

 as quickly available as that in the nitrate, but is 

 more so than that in any other form of organic 

 nitrogen. One would rarely go amiss in the pur- 

 chase of dried blood as a carrier of nitrogen if the 

 price were relatively as low as in the case of 

 nitrate of soda, but he should not let any preju- 

 dice in favor of animal origin of fertilizers lead 

 him to pay an excessive price per pound for the 

 nitrogen contained in it. Such a prejudice has 

 caused the nitrogen in a good red blood to sell for 

 one half more per pound than in nitrate of soda, 

 and it is not a good purchase on that basis. 



The lower grades of dried blood on the market 

 contain as low as 6 per cent of nitrogen, and the 

 animal refuse put into it gives it a content of a 

 few per cent of phosphoric acid. This black 

 blood is very variable in composition, and should 

 always be accompanied by a guaranteed analysis. 



Tankage. The waste from the slaughter of 

 animals goes into a product called tankage. The 

 refuse is cooked for removal of the fat, and then 

 ground. It may run high in nitrogen on account 

 of the amount of meat in the mixture, and it may 

 be low in nitrogen and very high in phosphoric 



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