18 Colorado Experiment Station 
It will be noticed that in 1913 the first foot of soil usually con¬ 
tained more nitrates than the succeeding three feet, except on 12 
May, whereas this is not true to the same extent in 1915. In other 
words, the frequent rains of 1915 caused the nitrates to pass below 
the first foot. This was not due to the difference in the amount of 
water received during the months considered, for that was approxi¬ 
mately the same during the respective seasons, about 19 inches, nor 
was it due to differences in soil, for we used the same plots, nor to 
the wheat, for we used the same varieties, but to the distribution of 
the water applied to the surface throughout the season. 
THE TOTAL NITROGEN 
On 27 June, 1913, we sampled three sections of soil to a depth 
of eleven feet, making a separate sample of each foot of the section. 
These samples agreed in showing that the surface foot contained, 
roughly, twice as much nitrogen as the second, and the second 
twice as much as the third, but from the third downward, including 
the eleventh foot, the amount of the total nitrogen remained fairly 
constant, at about 0.02 percent. In such, four-foot samples, we took 
during this season of 1913, six sets of them, the same fact was 
shown, i. e., that the total nitrogen in the fourth foot was about 
0.02 percent, or between this and 0.03 percent. These samples were 
taken from fallow land, but six sets taken from the cropped land 
showed essentially the same thing. We cannot say that the samples 
as taken showed any regular differences in the nitrogen in the first, 
or any succeeding foot in favor of the fallow land which would jus¬ 
tify any attempt to interpret them. 
In 1915 we determined the total nitrogen in 19 series of sam¬ 
ples taken to a depth of four feet. These agree in showing that the 
total nitrogen falls to an amount equal to from 0.02 to 0.03 percent 
in the fourth foot. The samples taken 13 May, before the plants 
had attained any considerable development, showed that the sur¬ 
face foot was perceptibly richer in total nitrogen than on the two 
subsequent dates, 1 September and 25 October, when these deter¬ 
minations were repeated. The same fact holds to even a greater ex¬ 
tent for the nitric nitrogen, as the table last given shows for the 
corresponding nitrates. Of course, we have in this question the two 
serious difficulties which confront us in this work, i. e., the diffi¬ 
culty of obtaining samples which are comparable even when taken 
from as nearly the same spot as possible without seeking the iden¬ 
tical spot where we made the preceding boring, and the further 
question in regard to the importance that we are justified in attach¬ 
ing to a few ten-thousandths or even thousandths of one percent. 
There can be no question but that differences as small as, or even 
smaller than, thousandths of one percent, not only may, but are, of 
significance in these problems. If any question be entertained on 
