NITROGEN, NITRIFICATION, NITROGENOUS MANURES 139 



151. Moisture Necessary for Nitrification. - - Nitrifica- 

 tion cannot take place in a soil deficient in moisture ; 

 as in all fermentation processes, moisture is necessary 

 for the chemical changes to occur. In a very dry time 

 nitrification is arrested for want of water. Water is as 

 necessary to 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. 



152. 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. 44 In northern latitudes nitrification 

 is checked during the winter, while in southern latitudes 

 this change takes place throughout the entire year. As 

 a result, many soils in southern latitudes contain less 

 nitrogen than soils in northern latitudes where forma- 

 tion and leaching of nitrates are checked by climatic 

 conditions. Crops which require their nitrogen early 

 in the growing season are frequently placed at a dis- 

 advantage because there is less available nitrogen in 

 the soil at that time than later. 



153. Strong Sunlight checks Nitrification. Nitrifica- 

 tion cannot take place in strong sunlight; it prevents 

 the action of all organisms of this class. In fallow land 

 there is no nitrification at the surface, but immediately 



