46 The Colorado Experiment Station 
rich in nitrates that the nitrogen fixing flora has practically per¬ 
ished. One thing is characteristic of them all, i. e., the brown color 
of the soil, hence the common term “black alkali.” This is most 
striking along the roadsides where we sometimes can observe the 
dark color continuous for as much as a mile at a time. No samples 
were taken from such places. The dark color is possibly due to 
the bacterial flora itself as the azotobacter form yellow brown or 
dark brown films. The following numbers are simply laboratory 
numbers for a preliminary series and may not again be presented, 
this of course is entirely in Professor Sackett’s hands. Professor 
Sackett found that these samples were comparatively rich in nitro¬ 
gen fixing bacteria of which he finds a considerable variety. It is 
not time to state any conclusion even tentatively held. Professor 
Sackett has given me the following results which may suffice for 
the present purpose, i. e., to place the source of these nitrates be¬ 
yond a reasonable doubt. The nine samples represent five localities. 
Number 1.—A surface soil very rich in nitrates. 
Number 2.—This sample is from the same locality taken to a depth of 
6 inches. 
Number 3.—Same locality 12-14 inches deep. 
Number 4.—Taken as normal soil for this locality, 2-6 inches deep, no 
water at a depth of five feet. 
Number 5.—Another locality from 2-6 inches deep. 
Number 6.—Another from 2-6 inches deep. 
Number 7.—Another locality from 2-6 inches deep. 
Number 8.—Normal soil near No. 7. 
Number 9.—A normal mesa soil in an alfalfa field with no apparent 
trouble. 
NITROGEN FIXATION. 
Milligrams Nitrogen Fixed in 100 CC. Mannite Solution, Infusion of 10 
Grams of Soil Added. 
10 Days 
20 Days 
30 Days 
Number 
1. 
. 0.00000 
0.00000 
1.05075 
Number 
2. 
. 0 00000 
1.19085 
0.56040 
Number 
3. 
. 1.78627 
3.08220 
3.43245 
Number 
4. 
. 3 92780 
6.16440 
12.46890 
Number 
5 . 
. 0.63045 
0.84060 
3.08220 
Number 
6. 
. 0.07213 
0.77055 
3.57265 
Number 
7 . 
.. . 1.72130 
3.50250 
3.01215 
Number 
8. 
. 1.87562 
2.38170 
2.87205 
Number 
9 . 
. 4.13431 
13.02930 
10.15725 
All questions of technique and further detail will be presented 
by Professor Sackett in due time. 
The great variety of soils in which I have observed this trouble 
and the variety of differences in the appearances of these places 
make one hopeful of very interesting results. 
We may be pardoned for adding the following consideration, 
possibly of some geological interest. The source of the nitrogen 
present in the Chile saltpetre beds has been the cause of much 
speculation. The source of the nitrogen in the India saltpetre earth 
is considered as evident and the formation of the nitrates is suf¬ 
ficiently accounted for by the action of nitrifying bacteria, which 
