64 AGRICULTURE 



required, and the result produced, are much 

 less than in the case of cereals. 



Another essential condition of nitrification 

 is a sufficient supply of moisture, but if water 

 in the soil is so abundant as materially to 

 reduce the supplies of air, or to keep the soil 

 cold, it may have a retarding rather than a 

 stimulating influence upon the process of 

 nitrification. 



Lastly, the conversion of organic or 

 ammoniacal nitrogen into nitric acid, and 

 finally into a nitrate, is dependent upon 

 the presence of a base with which the nitric 

 acid may combine as soon as it has been 

 formed. Nitric acid, as is well known to 

 those who have had any laboratory experi- 

 ence, is a highly corrosive substance, which, 

 if accumulating in quantity in the soil, would 

 immediately react upon the organisms pro- 

 ducing it, and put them out of action. There 

 is a law, applicable both to physical and 

 biological problems, that may be expressed 

 by saying that the accumulation of the 

 products of an action tends to put a stop to 

 that action. If, for instance, the product of 

 the action of nitrification, namely nitric 

 acid, be allowed to accumulate in the soil it 

 will quickly interfere with the activity of the 

 organisms, and compel them to cease working. 



