142 NITRIFICATION 



A very small quantity of free ammonia dr of ammonium 

 carbonate, which dissociates easily, also stops the growth 

 and multiplication of the nitrate organisms, but does not 

 much influence the oxidizing power of those already in 

 existence. Any nitrite formed in the soil may be 

 oxidized immediately to nitrate, even in the presence of 

 a certain amount of free ammonia, where species of 

 Nitrobacter are abundant. Generally, however, free 

 ammonia is absorbed at once and rendered inert by the 

 constituents of the soil. 



The nitrifying organisms are remarkable in possessing 

 the power of manufacturing the organic compounds needed 

 for growth and multiplication of their bodies from simple 

 inorganic salts and carbon dioxide. In this respect they 

 resemble green plants, but they carry on their work 

 without the assistance of chlorophyll or sunlight. The 

 energy necessary for the reduction of carbon dioxide is 

 derived from the oxidation of ammonium compounds ; 

 from 33 to 37 grams of nitrogen are oxidized for each 

 gram of carbon assimilated, a fact which to some extent 

 explains the extremely slow development of these 

 organisms. 



Every endeavour should be made by agriculturists to 

 assist the nitrifying organisms in their work of preparing 

 available nitrates for the needs of crops. The applica- 

 tion of lime, the removal of superfluous water from the 

 soil, and the provision of good aeration by thorough 

 cultivation, especially during summer, are among the 

 most important practices which can be adopted by 

 farmers for the stimulation of these useful soil organisms. 



Sulphate of ammonia and manures, which must be 

 nitrified before the nitrogen is available to plants, are 

 best applied to soils of light porous character in which 



