122 SOILS AND FERTILIZERS 



137. Moisture Necessary for Nitrification. — Nitri- 

 fication cannot take place in a soil deprived of mois- 

 ture. As in all fermentation processes, so with nitri- 

 fication, moisture is necessary for the chemical changes 

 to take place. In a very dry time nitrification is 

 arrested for the want of water. Water is as necessary 

 for the growth and development of the living organism 

 which carries on the work of nitrification, as it is to 

 the life of a plant of higher order. 



138. Temperatures Favorable for Nitrification. — 



The most favorable temperatures for nitrification are 

 between 12 C. (54 F.) and 37 C. (99 F.). It may 

 take place at as low a temperature as 3 or 4 C. 

 (37° and 39 F.); at 50 C. (122 F.) it is feeble, 

 while at 55 C. (130 F.) there is no action. 43 In 

 northern latitudes nitrification is checked during the 

 winter, while in southern latitudes this change takes 

 place during the entire year. Crops which re- 

 quire their nitrogen early in the growing season are 

 frequently placed at a disadvantage because there is less 

 available nitrogen in the soil at that time than later. 



139. Strong Sunlight Checks Nitrification. — Nitri- 

 fication cannot take place in strong sunlight ; it pre- 

 vents the action of all organisms of this class. In 

 fallow land there is no nitrification at the surface but 

 immediately below where the surface soil excludes the 

 sunlight, it is most active. In a cornfield it is more 

 active than in a compacted fallow field. 



