98 DEPARTMENT OF AGRICULTURE GEORGIA. | [384] 



pound, which, when applied to the soil, supplies available 

 plant food in such form as to be readily absorbed by the 

 roots of plants under natural circumstances. 



Fertilizing agents aid plants in appropriating plant-food 

 already in the soil without directly supplying it warmth 

 and moisture are fertilizing agents. 



The great bulk of the food of plants is derived from the 

 atmosphere, which is invariable in composition, and beyond 

 the control of human agencies. 



It is of such fertilizing substances as may be made tribu- 

 tary to plants through their application to the soil, the 

 productive capacity of which is, to a large degree, under the 

 control of the skillful agriculturist, that this chapter will 

 treat. 



The principal fertilizers of animal origin are fish, excre- 

 mentitious matters from animals and fowls, and the flesh, 

 blood, bones, horns, hoofs and hair of animals. 



Fish and fish scraps, the refuse from oil factories, are 

 used as a commercial source of ammonia, of which it con- 

 tains over five per cent, with a moderate per cent, of phos- 

 phoric acid. It is used for the purpose of supplying am- 

 monia to commercial compounds. 



The fish, however, decomposes so promptly that its ni- 

 trogen is, in a very short time, converted into actual am- 

 monia, which, being all promptly available, acts injuriously 

 in cases of drouth, and is exhausted before the period of 

 growth of our summer crops is completed. For the cot- 

 ton plant, which continues its growth throughout our long 

 summers, a part should be actual, and a part potential am- 

 monia, or nitrogen, in such a form as to be capable of being 

 converted into ammonia. In the case of fish, the decom- 

 position is so rapid that its entire nitrogen is promptly con- 

 verted into actual ammonia, and hence the tendency of 

 fertilizers, ammoniated with fish, to "fire" crops in times 

 of drouth. 



Excrement varies in its composition : 



