24 Fertilizers 



ganic form, in animal or vegetable matter, derived from 

 any form of life, which must first decay before it can serve 

 as plant-food. (2) As the decay goes on ammonia is 

 formed, and then (3) from the ammonia the nitrate is 

 formed, which is the form in which plants take up the 

 largest proportion of their nitrogen. This process is the 

 direct result of bacterial activity and is known as nitri- 

 fication. Inasmuch as products exist which contain 

 nitrogen in these three distinct forms, it is possible by their 

 use to control largely the feeding of the plant in respect 

 to this element, while in the case of natural manures, 

 the feeding of the plant with nitrogen depends upon 

 conditions which cause its change from the organic 

 into the other forms. As these conditions are variable, 

 the problem of the economical feeding of plants 

 with nitrogen, other things being equal, becomes a more 

 difficult matter with the natural than with the artificial 

 manures. 



Phosphoric acid also exists in different forms, the 

 form measuring to a large degree its availability: the 

 organic, in which the availability depends upon the 

 rapidity of decay; and the soluble and immediately 

 available form, that is, the form that distributes 

 everywhere, and which the plant can absorb immedi- 

 ately it comes in contact with the roots. Commercial 

 products exist which contain the phosphoric acid in these 

 distinct forms. The user is therefore enabled to supply 

 this constituent in such form as may best suit his crop and 

 soil conditions. 



In the case of potash, distinct forms, as muriate, sul- 

 fate and carbonate, also exist, though in the case of potash, 

 the form in which it is combined exerts less influence 

 upon the availability of the element to the plant than is 



