The Composition and Use or Fertilizers. 261 



(8) Leather varies in its rapidity of action according to its con- 

 dition. Raw leather is practically valueless as a source of nitro- 

 gen for plants. Boasted and steamed leather has a little more 

 value than raw leather, but is comparatively valueless. However, 

 the nitrogen in finely-ground leather that has been carefully 

 treated with sulphuric acid has a degree of availability about 

 equal to that of ground fish. 



(9) Cotton Seed Meal and Castor-Pomace, finely ground, fur- 

 nish nitrogen that is utilized by plants in about the same degree as 

 ground fish or even dried blood. 



Various experiments have been made to determine the com- 

 parative plant-food value of nitrogen in the more common animal 

 and vegetable materials. While the results have not been uni- 

 form, they serve as a fair guide. Taking results secured with 

 nitrate-nitrogen as 100, the following table can be made: 



TABLE Showing Comparative Plant-Food Value of Nitrogen in 

 Animal and Vegetable Materials. 



Availability or 

 crop produc- 

 ing value. 



Nitrate of soda 100 



Dried blood 70 



Cotton seed meal 70 



Castor-pomace 70 



Fish, dried and ground 68 



Horn and hoof meal 68 



Dissolved leather 65 



Steamed 15 



Koasted leather 10 



Raw leather 2 



It must be understood that the above figures are only approxi- 

 mate and are not of universal application. They indicate what is 

 fairly true when used on the same crop under the same conditions. 

 To illustrate: If by the application of 50 pounds of nitrate-nitrogen 

 we were able to increase a wheat crop 100 pounds an acre, the 

 application of the same amount of nitrogen in the form of dried 

 blood, cotton seed meal or castor-pomace would increase the crop 

 TO pounds an acre; the increased yield from use of dried fish, 

 horn and hoof meal would be 68 pounds; from raw leather, two 

 pounds, etc 



