24 
The Colorado Experiment Station. 
portion had remained practically unchanged, while the other showed 
a decided gain. This proved beyond a doubt that the nitrogen 
increase in the fallow ground was in some way intimately associated 
with the life of the soil microorganisms. Winogradsky, in 1892, 
succeeded in isolating an organism, Clostridium pastori:<num, which 
was capable of forming nitrogen compounds, under anaerobic con¬ 
ditions, in the culture medium which contained no nitrogen. A 
very valuable addition to our knowledge of the subject was made 
when Beijerinck, in 1901, reported his discovery of a group of 
large, aerobic bacteria capable of building up protein compounds 
from atmospheric nitrogen. To this group, he gave the name 
Azotobacter. Two species were described by him, Azotobacter 
chroococcum and Azotobacter agilis , and since then five or six 
others have been added to the list. Both the anaerobic and the 
aerobic forms are widely distributed in cultivated soils. In addition 
to these, a slight fixation has been secured with several of the 
ordinary soil bacteria but not enough to be of any economic im¬ 
portance. 
In this connection may be mentioned the commercial prepara¬ 
tion “Alinit,” a pure culture of Bacillus ellenbachensis, which was 
exploited a number of years ago in Germany as a panacea for worn 
out land. It was to be used for inoculating soil and by virtue of 
the nitrogen fixing bacteria which it contained, wonderful gains in 
nitrogen were to be expected. Like many such phenomenal dis¬ 
coveries, it failed to accomplish the extravagant claims made for it, 
and it was soon forgotten save for its record in the annals of science. 
Several attempts have been made to inoculate soil with pure 
cultures of Azotobacter but with little success. As with Alinit, the 
failure to secure satisfactory results have been due in a large meas¬ 
ure to unfavorable soil conditions, namely, acid soils, insufficient 
moisture, lack of basic carbonates, and mineral salts. 
While the mechanism of nitrogen fixation within the bacterial 
cell is not clearly understood, it is believed that the Azotobacter 
cell utilizes the nitrogen of the atmosphere to build up protein 
compounds. These in turn undergo decomposition, and through 
the action of the ammonifying and nitrifying organisms, they are 
converted into nitrates. 
It is believed that during the process of fixation, Azotobacter 
derives the energy for this function from the organic material 
present, and the results of certain experiments have shown that 
the amount of nitrogen taken up bears a definite relation to the 
quantity of carbonaceous material consumed. From this it follows 
