128 COTTON 



lizers, we find several materials for supplying 

 nitrogen : 



Nitrate of Soda or Chili Salt-peter is a white 

 solid which is mined in the rainless districts of 

 South America, especially in Chili and Peru. 

 When prepared for commercial use it contains 

 from 15 J to 16 per cent of nitrogen or 320 pounds 

 to the ton. 



Nitrate of soda dissolves easily in water, and 

 rapidly distributes itself through the soil where 

 plant roots can make use of it. The plants take 

 their nitrogen from the soil in the form of nitrate, 

 regardless of the source of supply, hence this 

 material is the most immediately available form 

 of plant food found in commercial substances. 

 When used in large quantities there is danger of 

 loss because of the ease with which the material 

 becomes soluble. 



Sulphate of Ammonia: This substance con- 

 tains about 20 per cent of nitrogen or 400 pounds 

 to the ton. While quite available it must be 

 changed first into nitrate form before being used by 

 plants. 



Dried Blood: Contains from 8 to 12 per cent of 

 nitrogen and 7 to 14 per cent of phosphoric acid, 

 and is the richest substance coming from animal 

 products. 



Tankage: A by-product of the slaughtering 

 house, contains from 4 to 8 per cent of nitrogen and 

 7 to 14 per cent of phosphoric acid. It slowly de- 

 composes in the soil, but is a valuable material 

 for cotton fertilizers. 



Dried Fish Scrap: This substance is a by- 

 product of the fish oil and canning factories. It 

 contains both nitrogen and phosphorus, there 



