Fixation of Nitrogkn in Colorado Soils 45 
is ill harmony with the results obtained by others in the exam- 
ination of deep well-waters. I think that the depth of 65 feet 
previously given is an unusual depth from which to obtain 
nitrates. In this case it is not a question of a few parts per 
million but of many. 
' NITRATES HIGH IN WELL-WATERS ONLY WHEN NI- 
TRATES ARE HIGH IN SURFACE SOIL 
'1 If we consider the various smaller areas within this sec- 
tion we will find the same facts obtaining. I have brought to- 
gether in the preceding table the nitric nitrogen in the soils 
and well-waters in such a manner that the results stand op- 
^ posite to each other. 
I Where the nitrates are high in the surface soil the well- 
waters are also high. I have previously made mention of the 
fact that one may ask, — does the nitric nitrogen in the water 
come from the soil or contrariwise: does the nitric nitroLren in 
' the soil come from the water? We have elsewhere shown that 
, our ground-waters carry no nitric nitrogen except they come 
[ from beneath a nitre-area and have given one instance in which 
a ground- water was very rich in nitric nitrogen, whereas water 
obtained at a depth only 10 feet below this ground-water con- 
tained no nitric nitrogen. The latter water evidently could not 
be the source of the nitrates in the ground-water. 
There is another possible explanation, to- wit: that this 
ground-water represents the leaching out of a large surround- 
I ing territory. This phase of the question was considered at 
length and in detail for a case in which the nitrates occurred 
; in large quantities and we could find no basis whatever to sup- 
; port this suggestion. 
Another source has been suggested, i.e., the waters used for 
irrigating the land. These waters have been examined very 
i many times in the past and we have uniformly found only small 
. amounts of nitric nitrogen usually less th m 0.5 p.p.m. The 
, maximum that I have record of is 1.5 p.p.m. for Arkansas River 
water taken at Rocky Ford which was a return water. If the 
! waters used for irrigating these lands were the source of the 
nitrates, their occurrence should be more general and in all 
! lands irrigated with this water, this is not the case. 
!; In describing the part of the Wellington district that is 
particularly discussed in this bulletin, I stated that the de- 
pressions were small, some of them not more than a mile wdde, 
;; and separated from the neighboring depression by a ridge so 
that drainage either into or out of them is difficult. The col- 
^ lectin g area for such a basin is very limited and each such 
