NITRIFICATION 103 



acre. In the making of composts the frequent stirring of 

 the pile favors the process of ainmonification, and of nitri- 

 fication especially. 



Nitrification goes on very slowly in acid soils, such as 

 marsh or peat soils. If these are treated with lime in such 

 quantities as to establish an alkaline reaction, the formation 

 of nitrates will be greatly increased. In water-logged soils 

 the decomposition of the organic matter is incomplete, and 

 the acid produced accumulates. The removal of the water 

 by drainage permits the air to enter, and thus gives oppor- 

 tunity for the growth of aerobic microorganisms, such as 

 molds, that will decompose the acids, making the soil a bet- 

 ter home for the nitrifying bacteria. 



The nitrification process goes on slowly at low tempera- 

 tures. It is probable that it continues as long as the soil is 

 not frozen. 



Conservation of nitrogen. When moisture and tempera- 

 ture conditions are most favorable for crop production, the 

 yield is often limited by the lack of sufficient quantities of 

 some one element. Generally speaking, this limiting ele- 

 ment is most often nitrogen. It is again probable that the 

 ammonia is oxidized as rapidly as it is formed, but not 

 sufficient ammonia is formed for the needs of the crop. As 

 has been indicated, the process of ammonification is favored 

 by the same conditions as are known to favor the process 

 of nitrification. The plant leads a sort of hand-to-mouth 

 existence, as far as the supply of nitrates is concerned, since 

 in the growing season the nitrates are used as fast as they 

 are formed. After the crop is removed the process of de- 

 composition continues, and the nitrates accumulate in the 

 soil, to be removed in the wet periods of the fall, winter 

 and spring. 



Since nitrogen is most frequently the element limiting 

 the growth of the crop, and since the store of nitrogen in 



