The Healthy Soil 



13 



the soil, three definite processes take place, all thanks 

 to the work of certain soil micro-organisms. 



1. Ammonification, In this process, the soil bac- 

 teria attack the complex proteids and convert them 

 into ammonia. The odor of ammonia from decom- 

 posed urea, manure, or any other organic matter is 

 always an indication that ammonification takes 

 place. According to Sackett * and others the ability 

 to bring about this change is attributed to the follow- 

 ing soil bacteria: Bacillus mycoides^ Bacillus pro- 

 teus vulgaris^ Bacillus mesentericus vulgatus^ Bacil- 

 lus suhtilis^ Bacillus janthinus^ Bacillus coli commu' 

 nis^ Bacillus megatherium^ Bacillus fluorescens lique- 

 faciens^ Bacillus fluorescens putidus and Sarcina 

 lutea. 



Recent investigations by Waksman f and others 

 indicate that certain classes of fungi are even 

 stronger ammonifiers than are bacteria. Trichoderma 

 Koningi and the Mucorales fungi were found to be 

 strong ammonifiers. Fungi, too, are very strong 

 cellulose decomposers. Further extensive investiga- 

 tions on soil fungi will no doubt more strongly es- 

 tablish their relationship to ammonification. 



2. Nitrification. In order to be readily available 

 for plants, ammonia and ammonia compounds must 

 be changed still further into simpler compounds or, 

 as the process is known, must undergo nitrification. 

 The ammonia is first oxidized into nitrous acid and 

 nitrates. This is accomplished by soil bacteria, Ni- 



♦Sackett, W. G., Colorado Agr. Expt. Sta. Bui. 196: 3-39, 1916. 

 t Waksman, A., Soil Science 2: 103-155, 1916. 



