NITROGEN AS AMINE OR PROTEIN 217 



running from 6 to 12 per cent. It may also carry 3 or 4 

 per cent, of phosphoric acid. 



The availability of the best grades of dried blood is roughly 

 three-fourths that of sodium nitrate, although it varies with 

 soil conditions. Its nitrogen is in the protein form and must 

 undergo the complete process of ammonification and nitri- 

 fication before becoming available. In cold, acid soils this 

 process is not so rapid and as a result dried blood is not a 

 good fertilizer for such soils. The nitrogen is not lost from 

 soils since leaching cannot take place except as the protein 

 nitrifies, and this is not rapid enough to cause loss. 



Dried blood has no marked effect on the soil, except that 

 its tendency is toward making a soil acid, it being organic 

 in nature and the decomposition of organic matter produces 

 organic acids. Nitrification also produces acids which must 

 be neutralized. But it must be remembered that the natural 

 tendency of cultivated and fertilized soils is toward acidity 

 and this condition should not be feared. Plenty of calcium 

 carbonate in the soil prevents acidity from appearing and 

 liming will overcome this condition if necessary (See Chapter 

 XII). 



162. Dried Meat, Meat Meal. — Refuse meat from slaughter 

 houses and packing houses, and waste from beef extract 

 factories are first rendered, that is, steamed under pressure 

 to remove fat, then dried and ground. Sometimes bones are 

 mixed with the meat before rendering, and in this case, 

 of course, the product contains phosphoric acid. The best 

 grades of dried meat carry 13 or 14 per cent, of nitrogen, 

 although many samples run less. 



The availability of meat meal is not quite so high as dried 

 blood, but it makes a very satisfactory nitrogenous fertilizer 

 when rapid availability is not wanted. Its nitrogen is in the 

 protein form and like that of dried blood is not lost by 

 leaching. Its effect on the soil is similar to that of dried 

 blood. 



163. Tankage. — Besides the refuse meat there are other 

 waste animal products that are used as fertilizers. Tendons, 

 intestines, lungs, and hair, together with bones, horns, and 

 hoofs are treated with steam under pressure to remove fat 



