THE RELEASE OF SOIL NITROGEN 



ate acceptance by plants, and the latter, also, although 

 not to the same degree maybe only after passing into a 

 nitrate form. 



The fact that nitrogen is a soil constituent, and one that 

 is easily and continually lost, makes the control of the 

 nitrogen supply the most serious problem of crop pro- 

 duction. 



Original sources of the nitrogen of the soil. The fol- 

 lowing are important sources of the nitrogen that plants 

 use : 



1. Organic matter from both the plant and the animal. 



2. Ammonia that is given by air, rain, and snow. 



3. Free nitrogen of the air that bacteria fix in the soil. 



4. The chemical salts supplied from other places. 



It matters not in just what form the nitrogen supply is 

 obtained. The two great sources of this supply are : or- 

 ganic matter and the bacterial contributions. 



Organic matter must be torn apart. If the stores of 

 plant food, locked in organic matter, are to be of benefit 

 to future generations of plants, it is necessary for the 

 many compounds contained therein to be destroyed: or- 

 ganized compounds must be torn apart and broken down 

 into simpler substances. This work is done by decom- 

 position, by decay and putrefaction, as we call them. 

 The former takes place in the presence of air when an 

 abundance of oxygen is found and the latter only in the 

 absence of much oxygen. 



The agents back of these performances are bacteria 

 tiny little plants that, unaided, neither eye can see nor 

 ear can hear, as they go on with their work, performing 

 their simple duties and their essential labors. 



And what do you think they are working for? Simply 

 carbon. They must have it. Just as bird or beast or man 

 looks to starch and fat and protein for life and suste- 



