524 VARIOUS FERTILITY FACTORS 



or brand tax of commercial fertilizers sold in his state, as a source 

 of revenue for the support of his department of investigation. 



FORMS AND SOURCES OF COMMERCIAL NITROGEN 



Aside from the free nitrogen of the air,, there are four distinct 

 " forms " of nitrogen : (i) organic nitrogen, (2) ammonia nitrogen, 

 (3) nitrate nitrogen, and (4) cyanamid nitrogen. 



Aside from farm manure and crop residues, the chief sources of 

 organic nitrogen are (i) dried blood and tankage from the slaughter 

 houses or stock yards, (2) cotton-seed meal from the oil refineries 

 in the South, and (3) fish-scrap in the Eastern and extreme West- 

 ern states. (Near the coast seaweed often becomes the staple 

 manure. It contains about as much nitrogen and phosphorus as 

 farm manure, and nearly five times as much potassium.) 



Dried blood. A good grade of dried blood contains 14 per cent 

 of nitrogen, while tankage is of various grades, ranging almost 

 from blood to bone. It contains much of the offal, and may include 

 the undigested contents of the stomach and intestinal tract. 

 One common grade is "7 and 30" tankage, meaning 7 per cent 

 of ammonia (NH 3 ) and 30 per cent of " bone phosphate," Ca 3 (PO 4 ) 2 , 

 corresponding to 6 per cent each of nitrogen and phosphorus. A 

 mixture containing about 2 parts of tankage, 3 or 4 parts of acid 

 phosphate, i part of kainit, and i or 2 parts of filler will produce 

 the " 2-8-2 formula," with about 2 per cent of "insoluble 

 phosphoric acid derived from animal bone." The annual pro- 

 duction of tankage and blood amounts to about i million tons. 



Dried peat. Train loads of dried peat are shipped from the peat 

 beds of Illinois and elsewhere to the fertilizer factories for use as a 

 filler; and as a filler it is said to be superior to all other materials, 

 because it is a very effective absorbent and thus keeps the acidu- 

 lated fertilizers in excellent mechanical condition. Dried peat con- 

 tains from 3 to 4 per cent of nitrogen which may be "found" by 

 analysis, although the nitrogen in peat is at best no more active 

 than that in the ordinary organic matter of the soil, which usually 

 amounts to 3000 to 5000 pounds per acre in the plowed soil, so 

 that 50 pounds of peat in 200 pounds of "complete" fertilizer 

 would not appreciably affect the crop. 



