NITROGEN IN SOILS 95 



portant compounds of nitrogen are those contained in 

 the organic matter. 



96. Nitrification. — All the nitrogen compounds of 

 plants are, as stated before, called by one name — 

 protein. When plants decay in the soil the protein 

 compounds are destroyed l»v the bacteria which feed 

 on the organic matter. Most of the nitrogen of the 

 protein compounds is finally changed by the processes 

 of decay into other compounds of nitrogen, which are 

 known as nitrates, and this change is called nitrifi- 

 cat 1 1 



All of the changes which the protein compounds 

 undergo in being converted into nitrates are caused 

 by bacteria, which work only under certain conditions. 

 These conditions have already been stated on page 78, 

 and they show that in temperate regions of the earth 

 nitrification can only take place during the summer 

 months. This is fortunate, for the nitrogen compounds 

 formed by this process are very easily dissolved in 

 water, and if not taken up by growing plants would he 

 quickly washed from the soil by rain water and so lost. 

 NitrifiY.iti >n can only take place in moist soils well 

 supplied with air, and is most active when the tem- 

 perature is between 95° and 100° P. Nitrification 

 when the temperature rises above 130° F. or 

 falls below 53° *\ The nitrates are easily dissolved in 



. and in this condition pass into the roo: 

 plants and are finally built dp by the growing plant 

 into fresh protein compounds. By this process of 

 nitrification the same nitrogen is need over and over 

 again. But, of course, there is always some loss of 



