A Study ot Colorado Wheat 5 
Realizing the weight of the misgivings that may be entertained 
regarding the applicability of laboratory results to this process of 
fixation, as it actually takes place in the f’eld, which we have assumed 
in the preceding paragraphs, we have endeavored to meet them by 
taking 3,000 pounds of soil from the field, and determining the fixing 
power of this soil. The details of this experiment do not belong in 
this place but the general results are apropos to the question just 
raised. 
The experiment was continued for 40 days under field condi¬ 
tions; the only departure from these that could possibly be urged 
against the experiment was that we endeavored to keep the moisture 
at uniformly 15.0 percent, it actually varied from this to 18.0 percent. 
We found the maximum gain in total nitrogen during the fourth 
week of the experiment, when the average for the surface foot show- 
'ed a gain of 45.5 p. p. m. 
This period was followed by a rapid increase in the rate of nitri¬ 
fication. We have no check on the loss of nitric-nitrogen by its mov¬ 
ing down to the bottom of our container and perhaps into the under¬ 
lying soil. The important fact in this connection is that at the end of 
40 days, this soil, to which noth’ng except ammonia-free distilled water 
had been added, showed a fixation of 36.0 p. p. m., calculated on the 
dry soil. 
This experiment was performed uiader field conditions, not in an 
incubator nor in a laboratory, but with the soil taken from the wheat 
field and kept out of doors. It was protected so that animals could 
not have access to it, and so that no washings from neighboring soil 
in event of rain, could be carried down on it, and the immediately 
adjacent soil was wet down constantly to prevent blowing of foreign 
soil onto it. 
We consider this conclusive proof that the laboratory resuics are 
applicable, and also that this soil fixes and nitrifies rapidly enough— 
we had an actual gain of 15.79 p. p. m. of nitric-nitrogen—to justify 
every claim made in this connection. 
While I am persuaded that field samples can not be depended 
upon in the study of fixation, this is not the case with nitrification, for 
this nitrogen exists in a definite form which can be determined in its 
totality at any time with a very high degree of accuracy. That there 
is difficulty in obtaining representative samples does not need to be 
stated. 
EFFECT OF WHEAT CROP ON FIXATION OF NITROGEN 
We have followed the amounts of nitrates present in our soils 
for two years, and have shown that the amounts of nitrogen present 
in our soils in this form at different times vary greatly. After a 
thorough soaking of the land, or if the land is occupied by a good 
