The Colorado Experiment Station. 
14 
maintaining the soil-nitrogen by the application of manure or com¬ 
mercial fertilizer, it will be but a few years, relatively speaking, un¬ 
til our fields will be unproductive and worthless. 
During their growth, green plants use nitrates to build up com¬ 
plex nitrogenous compounds which we call proteids, and the ani¬ 
mals which feed upon them, convert these proteids into still differ¬ 
ent forms. Such substances as bone glue or glutin, mucus, gelatine, 
egg albumin, legumin and the fibrin of the blood are produced in 
this manner. A portion of the proteid appropriated by animals is 
retained throughout life, but a second part is consumed by the body 
to furnish heat and energy. However, while this is going on, the 
proteid is being broken to pieces. Much of the carbon is oxidized 
and exhaled as carbon dioxide, while the waste nitrogen is carried 
off by the kidneys as urea in the urine. I11 this way, the complex 
nitrogen molecule is considerably simplified, but not to such a de¬ 
gree that the resulting compounds are of any immediate benefit to 
plants. It has been estimated that the human race alone excretes 
38,000 tons of urea daily, to which must be added the much greater 
amount voided by animals. In the light of this fact, does it not be¬ 
hoove all thrifty farmers to provide some means for conserving 
the liquid manure around the stables. Who knows how long such 
thoughtless waste is to go unpunished? 
When these same plants and animals die, and they are returned 
to the soil, quantities of nitrogen remain locked up in the complex 
proteid compounds of their bodies. Neither they nor the urea, just 
mentioned, are of any use whatsoever to future plant generations 
unless their nitrogen can be converted into nitrates. Thanks to the 
presence of soil micro-organisms, a means has been provided by 
which the complex nitrogenous compounds in decaying organic mat¬ 
ter can be converted into- nitrates, and if the agriculturist will see 
to it that his land receives a reasonable amount of organic nitrogen 
from year to year, either as stable manure or green crops, and if he, 
himself, is equally diligent in the cultivation and irrigation of his 
soil, there need be no alarm over a nitrogen famine. 
A mmonification. 
In the transformation of the nitrogen of proteid bodies and 
their cleavage products we recognize three well defined stages. The 
first of these deals with the production of ammonia by bacteria from 
the complex organic matter; in the second, the ammonia nitrogen is 
converted into nitrous acid and nitrites, and in the third, the ni¬ 
trites are changed into nitric acid and nitrates. The term “Am- 
monification” is applied to the first process while the combined 
