the: nitrifying efficiency of certain COLORADO SOILS 
5 
There is no need of attempting to trace the origin of these ac¬ 
cumulations to the concentration at the surface of the salts in the 
ground waters containing a hypothetical nitrate; moreover, granted 
that a ground water could be found independent of a niter area, which 
was rich in nitrates and which underlay the tract in question, why 
should we not find the nitrate and the brown color, as well as f,l e 
sulfates and chlorides, distributed uniformally over the hundreds of 
square miles which are involved in this trouble ? This is not the case. 
In this connection, it may be said that Dr. Headden had made a 
very careful study of the ground-waters of Colorado previous to the 
appearance of the niter trouble and had failed to find more than a 
mere trace of nitrates. Since then, he has followed up this phase of 
the question, and except where the ground-water flows under a niter 
area, from which it unquestionably receives the salt by leaching from 
above, he finds the nitrates present only in negligible quantities. In 
order to obtain the quantity of nitrates from our ground-waters which 
we meet in the brown spots, the evaporation of many acre feet of 
water and many years of time would be required. Furthermore, the 
chlorides and sulphates which would come from the evaporation of this 
immense amount of ground-water would be sufficient to cover the land 
with a white deposit many feet deep. Illustrative of the case, Dr. 
Headden (i.) gives the following: 
“We will not consider any greater depth of soil than is represented 
by our samples, i. e., two inches, but we will calculate how much of 
this drain water would be required to furnish the nitrate which we 
actually find in these two inches of soil, and we take this as 2,150 
pounds. The samples of soil and drain water were taken in May, 1911. 
'The drain water contains o. 1 part per million of nitric nitrogen, equiv¬ 
alent to 0.6 parts per million sodic nitrate; taking an acre foot at 2.7 
million pounds it gives us 1.62 pounds of nitrates per acre foot of water 
and we would have to evaporate 1,327 acre-feet of this drain water to 
obtain this 2,150 pounds of nitrates which we find present at this time. 
The evaporation of this amount of water would require, assuming that 
the annual evaporation amounted to sixty inches (At Fort Collins it is 
only 41 mches) two hundred and sixty-five years. This drain water 
carries 8,489 parts of total solids per million which, calculated on the 
1,327 acre-feet of water necessary to yield the 2,150 pounds of nitrates, 
would yield 30,414,840 pounds of salts, a quantity sufficient to cover 
the land more than seven feet deep, if we suppose them to have the 
same density as the soil itself.” 
“The changes- in the conditions of these soils have taken place 
within the past few, say six, years and these conclusions to which we 
are forced, if we suppose that these nitrates have their origin in the 
ground-waters, are evidently false. We know that no 1,327 acre-feet 
of water have evaporated to dryness on this land in this time an t it is 
evident that our country is not covered nearly eight feet deep with 
(,1) Fixation of Nitrogen in Some Colorado Soils, Wm. P. Headden, Bui. 178, Colo. 
Exp. Sta., p. 28, 43, 1912. 
