4 
COLORADO EXPERIMENT STATION 
the destruction of the crop, appears to have been lessened somewhat. 
A full description of the characteristic appearance and manner in 
which fruit trees and cultivated crops succumb to the trouble, here re¬ 
ferred to, has been given elsewhere (i) and a further elaboration of this 
feature is unnecessary at this time. 
This condition of the soil which has resulted so seriously to the 
agricultural and horticultural interests of the state has been shown by 
Dr. Headden to be due to the presence of large quantities of nitrates. 
To one who is accustomed to think of these salts in thousandths and 
ten-thousandths of a per cent., as they occur in the east and south, the 
quantities which we find in our niter sections must seem preposterous. 
However, one visit to the troubled districts is usually sufficient to con¬ 
vince the most skeptical. It is not uncommon to find the nitrates in some 
of the brown spots making up from two to six per cent, of the weight of 
the air dried soil. From this, it will be seen at a glance that our prob¬ 
lem is not one involving pounds but rather tons of nitrates. For ex¬ 
ample, we have the analysis of the soil from an orchard where the 
samples were taken to a depth of one foot; it carried 2.873 P er cent, of 
nitrates, corresponding to 113,480 pounds or 56.74 tons per acre foot. 
This does not represent an isolated brown spot a few feet in diameter 
but an area of ten to twelve acres, being a portion of a forty acre tract; 
again, in another sample, taken to a depth of five inches, the area in¬ 
volved being about eight acres, sodic nitrate corresponding to 344,000 
pounds or 172 tons was found; in the top five inches of another eight 
acre tract the equivalent of 189,971 pounds or 95 tons was present. Dr. 
Headden has examined sample after sample from the affected districts 
and all his analysis tell essentially the same story—excessive nitrates. 
The difference which we find between the niter content of the 
brown spots and that of the adjoining apparently normal soil is rather 
striking. A sample of the brown crust from the side of an irrigating 
furrow in an apple orchard contained 640 parts per million of nitrate 
nitrogen, while two and one-half feet away, the surface four-inches of 
normal soil gave 34 parts. The surface half-inch from the top of the 
ridge of an irrigating furrow in a deserted oat field including the 
brown crust showed 1360 parts per million of nitrate nitrogen, while 
six feet from the edge of the mottled brown area, the normal soil con¬ 
tained but 46 parts. To' the writer, this seems to suggest rather strongly 
the probability that the brown patches are purely local surface-forma¬ 
tions, which are actively engaged in building up nitrates in situ, espec¬ 
ially since the areas are increasing daily both in number and in size. 
Furthermore, we are now in position to present a complete chain of ex¬ 
perimental evidence to show beyond all reasonable doubt that these 
niter areas in the incipient stage of their formation, if not in the later 
stages as well, contain within themselves all the agents necessary to 
bring about their existence. 
(1) Bakteriologische Untersuchungen uber die Stickstoffbindurg in gewissen Bodenarten 
von Colorado. Cent. f. Bakt., II Abt., Bd. 34, No. 4-7. S. 81-114, i912. 
Bacteriological Studies of the Fixation of Nitrogen in Certain Colorado Soils, Bui. 179, 
Colorado Experiment Station, 1911. 
