136 



SOILS AND FERTILIZERS 



gen of the soil to the form of nitrates or nitrites. 

 Broadly speaking, it is the process by which the inert 

 nitrogen of the soil is rendered available as crop food. 

 The organisms which carry on the work of nitrification 

 were first isolated and studied by Winogradsky. 



148. Conditions Necessary for Nitrification are : 



1. Presence of the nitrifying organisms and food for 

 them. 



2. A supply of oxygen. 



3. Moisture. 



4. A favorable temperature. 



5. Absence of strong sunlight. 



6. The presence of some basic compound. 



In order to allow nitrification to proceed, all of these 

 conditions must be satisfied. The process is frequently 

 checked because some of the conditions, as presence of 

 a basic compound, are unfulfilled. 



FIG. 32. Nitrous Acid Organisms. (After Winogradsky.) 



