356 EXPERIMENT STATION RECORD. 



stationary in the lot of soil wbicli bad been sterilized.' It should b© 

 observed here that the ferments which briu^ about the transformation 

 of nitrogenous matter into ammonia are very resistant, and that if they 

 are subjected to 10(P for only a short time they are not completely 

 destroyed. It is necessary to subject them to a temperature of 120'^ tor 

 several hours in order to completely check their activity. 



Miintz and Condon bave isolated and cultivated several of the micro- 

 organisms of the soil and have found that almost all of tliem possess 

 the property of forming- ammonia. The organisms which bring about 

 this transformation are very numerous and belong to widely separated 

 species, being found not only among the molds but also among the 

 bacilli and micrococci. Ammoniacal fermentation is not due, therefore, 

 to a particular species, but is a function possessed in common by a large 

 number of species. A young Belgian agriculturist, E. Marclial, has 

 suggested that in arable soils the action of bacteria is predominant, 

 while in liumus soils of an acid reaction, such as those of meadows, the 

 formation of ammonia is due in large part to the molds.^ 



In very moist soils highly charged with humus, where the air circu- 

 lates with diflicultyj ammonia predominates and serves as plant food, 

 but in well cultivated soils thoroughly aerated the transformation to 

 nitric nitrogen is very rapid and complete. The different phases of this 

 transformation will be discussed in the following pages. 



FORMATION OF NITRATES IN THE SOIL — DISCOVERY t)F' THE NITRIC 



ferment: 



It was held for a long time that nitrification of ammonia was due 

 simply to chenucal action. A celebrated experiment by the well-known 

 chemist Kuhlmann served to confirm this erroneous view. He observed 

 that when a current of air charged with ammonia was conducted over 

 sijongy platinum, or better, platinum black, gently heated, the ammonia 

 was burned, its hydrogen lorming water and its nitrogen nitrous 

 vapors. 



This experiment led.to extravagant generalizations. It was held that 

 when saltpeter appeared on the walls of stables or sheepfolds, or in 

 the soil of a cave, it \\ as due to ammonia which had been burned by 

 oxygen under the influence of a porous body acting in the same man- 

 ner as the platinum black. The porous body to which was attributed 

 the property of favoring the combustion was supposed to be the 

 rough walls or the soil. This view was held until 1862, when Pasteur 

 observed that almost all slow combustions are brought about by micro- 

 organisms. Alcohol, for example, is not transformed by oxidation into 

 acetic acid m the process of vinegar-making until the surface of the 

 liquid to be acetified is covered by a thin veil of the white mold (Myco- 

 (lerma aceti). Should not the oxidation of ammonia and its trausfoima- 



' Anu. Agrou., 19, p. 209. =Anu. Agrou., 19, p. 506, 



