The Fixation of Nitrogen in Colorado Soils 37 
holes 1 and 6 we find the reverse to be the case. This is shown very 
markedly in the results obtained with the samples taken in Hole 
No. 1. in which we have 422.7 p. p. m. in the top three inches and 
only o. 1 p. p. m. at a depth of 4/4 feet. Hole No. 6 shows the 
same facts, but the amounts of nitric nitrogen involved are so small. 
24 p. p. m., being the maximum, that it, for our present purposes, 
may be neglected. The spot where Hole No. 1 was dug, had 
probably failed to receive any considerable irrigation and the whole 
summer’s formation had probably remained at the surface. This 
is suggested by the fact that the sample of ground-water taken from 
this hole at this time, contained only 4 p. p. m. nitric nitrogen, a 
quantity less than is found in some deep wells. The total solids in 
this water, however, was nearly 10.000 p. p. m. The hole dug close 
to this at the next sampling showed the same facts quite as strikingly 
as this one. In these samples we determined the water-soluble to 
see if there could be discovered any relation between this factor and 
the nitrates. We obtained for the surface three inches of soil the 
following results: Water-soluble. 13.475 P- P- m.; nitric nitrogen, 
2 37-4 P- P- ; for the twelve inches from 44 to 55 inches inclusive, 
water-soluble 17,925 p. p. m.; nitric nitrogen 6.0 p. p. m. We find 
the nitric nitrogen to diminish very rapidly with even slight depths, 
unless it has been carried down by rain or irrigating water, and in 
this land we nowhere find excessive quantities of nitrates, except 
where we can readily and with certainty recognize the brown pig¬ 
mentation of the Azotobacter. The nitric nitrogen found in the 
surface section, three inches, is less than is found for the com¬ 
posite sample made up of 60 samples representing a sixth of 
an acre. 
The extremely variable results obtained by taking such sections 
of soil is well shown by these 19 sections, as the numbers in each 
set have the same significance. The three sections numbered 1 
were taken as close together as I deemed advisable, so of number 2 
and the succeeding ones. I fear lest I erred in taking them a little 
too close together. Holes 1 and 4 were only about 55 feet from 
one another and yet we find altogether different conditions, and 
the same is true of holes 2 and 5, which were the same distance 
apart. The same may be said of these taken in pairs the other way, 
i. e., 1 and 2, 4 and 5. We observe the same irregularity on the 
surface of the soil and we can, using the brown color as a guide, 
pick out these irregularities with all certainty. Hole No. 6 was 
located in ground that was bad in 1911 but showed no injury in 
1912, while the Hole No. 7 was located in territory that has never 
shown any trouble. We find the nitric nitrogen in the samples 
