THE FIXATION OF NITROGEN IN SOME COLORADO SOILS 
A Further Stud [y 
By WM. P. HEADDEN 
INTRODUCTION. 
In Bulletin 155, of this station, I endeavored to demonstrate 
the occurrence of large quantities of nitrates in some of our Colo¬ 
rado soils by giving a number of analyses showing the presence 
of phenomenal quantities of these salts. So far as I have been 
able to learn it will undoubtedly be wise to lay emphasis upon this 
fact as its importance is fundamental; therefore, I shall give further 
examples of this occurrence though it seems that it ought to be a 
superfluous task. 
A second point which I endeavored to make perfectly plain 
was that I was writing not only of an extreme degree of concen¬ 
tration of nitrates in the soil but that this concentration pertained 
to large areas. Though I endeavored to write very conservatively 
I mentioned areas of eight, ten and twelve acres, as having been 
rendered barren by the accumulation of this salt, nitre, which term 
was used to designate any nitrate, calcic, magnesic, sodic or potassic 
nitrate, the essential point being the presence of nitric acid. 
Again I endeavored to show that any transportation, leaching 
and subsequent concentration was inadequate to account for the 
occurrences of these salts, because they occur on high mesas where 
there is no wash or transportation from higher lands as well as in 
low lands. In writing of the presence of nitrates in the waters 
issuing from the shales, I recognized the fact that it might suggest 
these shales as the source of the nitrates and endeavored to show 
that such a conclusion would be unwarranted, for the shales in 
question contain only 0.03 percent of nitrates and the presence of 
this small amount was probably due to the water from the higher 
lying mesas where nitrates occur rather abundantly, which fact is 
stated in Bulletin 155, p. 42, as follows: “The mesas above these 
shales are cultivated and bad nitre spots occur on top of them, 
in one case.80 feet above the level at which the water was taken/’ 
Further, that nitre spots occur in different geological formations 
where these shales do not occur, in alluvial deposits and under our 
ordinary prairie conditions; in other words, the shales, considered 
as a source of nitre, would not be available for the explanation of 
the greater part of the occurrences and we are compelled, on account 
of their insufficiency, to seek for a more generally occurring source 
or a cause sufficient to account for all the occurrences, assuming 
that they have a common cause, which is reasonable, at least, until 
we are sure that they have different causes in different places. 
