Commercial Fertilizers. 151 



known as red and black blood. The red variety has been more 

 carefully dried, while the black blood has resulted from a too 

 rapid drying. The red blood contains from 13 to 14 per cent 

 of nitrogen, while the black variety is less constant in composi- 

 tion and contains from 6 to 12 per cent. Dried blood ferments 

 very readily in the soil and is one of the most valuable organic 

 materials. 



Meat scrap or meat meal. This is a packing house product 

 and consists of various parts of animal bodies that have been 

 kept separate from the tankage. It is rather variable in com- 

 position, containing usually from 10 to 12 ]5er cent of nitrogen, 

 with a small amount of phosphoric acid about 3 per cent. It 

 is often used for feeding purposes, as well as for fertilizer. 



Tankage. This is a general mixture of the refuse material 

 from the slaughter houses. It has usually been steam-cooked in 

 order to separate the fat and gelatine, a process which renders it 

 more easily fermentable in the soil. From the great variations 

 in the nature of the materials entering into its make-up, it must 

 of necesssity have a variable composition. It contains from 4 

 to 9 per cent of nitrogen and from 3 to 12 per cent of phosphoric 

 acid. It is a valuable form of fertilizer as it supplies the crop 

 with both nitrogen and phosphoric acid. 



Dried fish and fish scrap. Most of the fish fertilizers are 

 made from menhaden, a fish that is caught in large numbers 

 ^along the Atlantic coast. The fish are steamed and pressed to 

 extract the oil and the remaining '^pLQmace" is dried and ground. 

 This material contains from 8 to 11 per -cent of nitrogen and 

 3 to 5 per cent of phosphoric acid. Some of Itefish fertilizers 

 consist of the residue of the canning factories, but these are not 

 considered so valuable as those derived from menhaden. This 

 material readily undergoes nitrification and is a quick acting 

 fertilizer. 



Cotton-seed meal. This is obtained by removing the hulls 

 and oil from the cotton seed. The material is then ground and 

 put upon th' market. It contains about 7 per cent of nitrogen. 



