The) Fixation of Nitrogen in Colorado Soils 27 
our samples at stated times at this place were so great that we suc¬ 
ceeded in collecting only a few samples, which we will give as mis¬ 
cellaneous ones. They will be none the less interesting on this ac¬ 
count. Perhaps they may be even more instructive. As just stated, 
a few years ago there were no pronounced, characteristic “brown 
spots” noticeable. There probably was, in many places, an abund¬ 
ance, perhaps an excess of nitrates, but for the past four or it may 
be five years there has been no doubt about their presence. The 
first sample that I will give was taken from a wheat field 4 May, 
1912. The soil was a red, mesa clay. The surface was quite white. 
We judged this to be a case of ordinary alkali. In sampling, only 
the surface soil was taken, and we obtained the following results 
in parts per million: 
ANALYSES OF SAMPLES FROM THE FOURTH PLACE CHOSEN. 
Nitric 
Total 
Nitrogen 
Nitrogen 
Chlorin 
Ordinary alkali soil . . 
516.8 
6,031.8 
Ordinary alkali surface 
soil . 
. 80.0 
693.6 
6,922.0 
Brown surface soil . . . 
1,360.0 
11,416.0 
Very brown spot . 
5,548.8 
17,016.0 
Ordinary soil 50 feet away.. 
. 12.0 
612.0 
45.3 
White alkali soil .... 
1,319.2 
23,584.0 
Brown spot . 
3,631.2 
24,038.0 
Brown spot . 
1,672.8 
18,678.0 
Very brown spot . 
6,629.6 
19,692.0 
Twenty feet outside of 
spot. 
. 2.0 
435.2 
206.2 
White alkali soil . 
1,210.4 
18,117.0 
This whole group that we have given as miscellaneous samples 
was collected within an area of less than five miles in length by 
one-half mile in width. Some of the spots are small but the last 
white alkali soil given was from a field of probably forty acres. 
An important question suggests itself in connection with the 
fact that the surface portions of these spots are often, but not 
always, rich in chlorin. The same thing is true of the surface por¬ 
tions of some other lands where there are no nitrates. There seems 
to be no general rule which holds good for all soils in regard to the 
concentration of the chlorin near or at the surface of the soil. We 
have given cases in which the surface salts were very rich in chlorin 
and the nitrates were practically absent, and we have also given 
samples in which the nitrates were very abundant and the chlorin, 
or the equivalent chlorids, were subordinate in quantity. We have 
further seen that the ground-water at a depth of about four and 
one-sixth feet, may be quite rich in nitrates and the surface soil 
be very poor in them. The water here referred to carries 318.8 
p. p. m. while the surface soil carried 53.0 p. p. m., and the second 
section, 4 to 7 inches inclusive, carried 3.5 p. p. m. of nitric nitrogen. 
