206 THE PRINCIPLES OF AGRICULTURE 



SUGGESTIONS ON CHAPTER XIII 



338a. It is remarkable how the value of manurt increases 

 with the age of the country and the intensity of the agriculture. 

 This comes as a result of experience, wholly without the teachings 

 of science, although science explains why manure is valuable, 

 and points out many of the limitations of its use. The pros- 

 perity of the German peasant is measured by the size of his 

 manure-pile. Gardeners place the greatest dependence upon 

 manure ; but they want it well rotted, which means that they 

 not only want its plant-food in the most available condition, but 

 that they desire to utilize it largely for its mechanical effect in 

 loosening the soil with which it is mixed. 



341a. A ton of clover hay removes about forty pounds of 

 nitrogen, ten pounds of phosphoric acid and forty pounds of 

 potash. A ton of butter removes about two and one-half pounds 

 of nitrogen, and less than one pound each of phosphoric acid and 

 potash. 



346a. "Tankage is a highly nitrogenous product, and con- 

 sists chiefly of the dried animal wastes from the large abattoirs 

 and slaughtering establishments. It is variable in its composition, 

 since it includes the otherwise unusable parts of the carcass, as 

 bone, tendons, flesh, hair, etc. The portions of this from the 

 different animals not only vary in their composition, but they are 

 used in varying proportions, which naturally results in an ex- 

 tremely variable product. What is known as 'concentrated 

 tankage,' which is obtained by evaporating the fluids which con- 

 tain certain extractive animal matter, is the richest in nitrogen, 

 and is more uniform in character than the others ; and because of 

 its fineness of division and physical character, the nitrogen con- 

 tained in it is also more active than in the other forms." Voor- 

 hees, Fertilizers, 43. 



346&. Many other animal substances are used for fertilizers. 

 Those which are used for their nitrogen are dried blood, dried 

 meat, dried and ground fish, sea crabs, hoof meal. Those which 

 are used for phosphates are the various forms and preparations of 



