1907.] MOST ECONOMICAL SOURCES OF NITROGEN. I59 



before it serves as plant food. If in every stable there should 

 be kept a supply of ground phosphate rock and this phosphate 

 rock be freely used in dusting the stable floors and the gutter 

 and if it were sprinkled freely over the manure itself, it would 

 serve not only to prevent losses of ammonia, but owing to the 

 fermentation which takes place in the manure, phosphoric acid 

 itself would gradually be changed from the insoluble form into 

 the form available for plant food. Nearly all forms of phos- 

 phoric acid are being purchased. This is without doubt the 

 wisest practice, but would it not be a wiser practice to 

 purchase this phosphoric acid, at least a part of it, in the form 

 of ground rock, or floats, and by the use of this material in the 

 stables save the ammonia which would otherwise disappear. 



In every fertile soil there takes place what is known as 

 nitrification. Nitrification is the changing of the nitrogen of 

 organic compounds into the form of nitrates and nitrate 

 nitrogen is that form of nitrogen which is immediately avail- 

 able for the plants' use. 



While there is much about this mysterious process of 

 nitrification which is not yet understood, yet we have learned 

 some things definite with reference to it during the past few 

 years. We have learned that in order to have this take place 

 there must be in the soil compounds containing nitrogen. 

 These organic compounds may consist of rye which has been 

 plowed under, of sod from grass lands, of various legumes or 

 even from farm manures. In addition to these organic com- 

 pounds containing nitrogen, there must be present oxygen, 

 moisture but not saturated with water, proper temperature 

 and the presence of certain organisms known as nitrifying 

 bacteria. All of these things being present there is still one 

 other condition which must be secured before these bacteria 

 begin their work and that condition is an alkaline soil. This 

 alkaline soil may be secured by applications of lime or wood 

 ashes, but it must be secured if nitrates are to be formed in the 

 soil. These nitrates are formed most rapidly during the season 

 when nitrogen is most required by the growing plants. During 

 June, July and early August, the formation of nitrates may 

 take place very rapidly in the soil and there may be in the soil 

 nitrates secured in excess of the nitrates used by the growing 

 plants. As fall approaches and the soil becomes colder, nitri- 

 fication lessens and finally ceases at the approach of winter. 



