4 
Coi.oRADO Experiment Station 
tained throuj^hout, even when an area of 8, 10 or more acres 
was indicated, — were very much richer in nitrogen than ordi- 
nary soil and it was suggested that this nitrogen was derived 
from the air by the micro-flora of the soil. Later the power 
of these soils to fix nitrogen, i.e., to take it from the air, was 
shown by direct experiment. The amounts fixed under labora- 
tory conditions were very considerable. The results actuallv 
obtained showed that, had the rate of fixation continued for one 
year, the top two inches of soil would have appropriated as 
much nitrogen as is contained in 2.8 tons of sodic nitrate. The 
only new feature in this suggestion was that this fixation may 
be accomplished on so large a scale and with such an intensity. 
We also showed that nitrification, as well as fixation, goes 
on very rapidly in these soils. The maximum increase obtained 
l)y laboratory experiments in the amount of nitrogen in the 
form of nitrates was 138 percent in 48 days. Observations wei'e 
made on the increase of this form of nitrogen in the field for 
several months — from the beginning of August till the latter 
]uart of November. Our results are given in pounds per acre 
of sodic nitrate equivalent to the nitric nitrogen found in the 
top 4 feet of the soil. This land had been cropped to wheat. 
We found for four sections taken 1 August, 91.9, 51.7, 51.4 and 
38.9 pounds of sodic nitrate; on 22 November, the same plots 
yielded 179.0, 136.3, 154.3, and 191.6 pounds. The August sam- 
])les Avere taken just at the time the crop ripened and the No- ; 
vember ones almost 4 months later. The crop was harvested ■ 
10 August. These results show that nitrification goes on ; 
rapidly in the soil as soon as the crop is removed. We see i 
that w^e liaA^e, in practicallv 3^/2 months, an increase of from 
tAA o to fiAT^fold in this form of nitrogen. 
The distribution of this nitric nitrogen was also determined 
])oth in cropped land and in the nitre-spots. It is the latter 
only that interests us at this time. Bulletin 186 ])resents a 
study of this phase of the subject. The question of general i 
distribution and the possibility of subsequent concentration to ' 
account for the nitrates found in these spots is considered at 
length and the conclusion arrived at, that we have no grounds 
for assuming that such concentrations have taken place, on 
the contrary, we showed tliat in the case of some areas, very 
rich in nitrates, such concentrations could not have taken place. i 
Further, that these nitrates and our ordinary alkalis do not ! 
have a common origin. Further that it is only the surface ]ior- 
tions of these nitre-spots that are excessively rich in nitrales. 
It is, however, recognized that they may be Avashed doAvn ii^io 
