44 The Colorado Experiment Station 
only small amounts of, or no, nitrates. We mentioned nitrate areas in 
locations surrounded on three sides by alkali and seeped lands, but these 
locations themselves are well drained. The nitrates in these locations 
are not derived from the alkalis and seepage water from these adjacent 
lands for the following reasons: These adjacent lands contain only such 
quantities of nitric nitrogen as soils in general may contain. The alkalis, 
even the efflorescent ones, taken together with the surface portion of the 
soil, contain no nitrates; the ground-water underlying this seeped section 
contained no nitrates, therefore this land, though rich in alkalis and 
seeped, could not be the source of the nitrates found in the nitre areas. 
Further the drain-waters flowing from a drain laid through a portion of 
this land, but not under a nitre area, while comparatively rich in alkalis, 
carrying some 9,000 parts total solids per million, carried only 0.1 p. p. m. 
of nitric nitrogen. The nitrates found in these spots could not have been 
derived ready formed from these outside sources. The land was well 
drained; three out of five drains laid in this land drew no water except 
after irrigation. There is no unusual amount of the ordinary alkalis in 
this soil. Vegetation does well in this land except in these spots. The 
soil itself, except in these spots, is not rich in nitrogen and here it seems 
to be largely in the form of nitrates. The evaporation of the ground- 
water that underlies this land would yield large amounts of the ordinary 
alkalis but no nitrates, or very small amounts, and as the land is level 
and uniform in character and texture, there is no reason why the deposi¬ 
tion should not be general over the surface and not confined to spots. 
The fact is that the nitrates are confined to the brown spots. All of these 
considerations were weighed before Bulletin 155 was written, and the 
question asked, whence comes the nitrogen. Our investigations had shown 
that it did not come from the adjoining lands, nor from below and the 
land itself does not ordinarily contain it, but still there is no question of 
its presence. It was not always there, for the beginning and cause of 
this trouble had been observed and unsuccessfully combated. In 1904 
this land was free from this trouble, in 1909 apple trees and garden 
vegetables could not maintain themselves against its influence. Besides, 
the spots were extending their boundaries. It was not a stationary thing, 
but was growing. The adjacent land had in the meantime not changed 
materially; it continued to be barren of nitrates, but the seepage condi¬ 
tion was growing worse; this, however, did not, and does not now affect 
this land. Between 19 06 and 1908 the trouble began to be recognized 
here and there without knowledge of its cause, but in 1909 it began to 
destroy orchards over larger areas, and the nitrates were recognized as 
the direct cause of this. From 1909 on, the annual loss of trees due to 
this cause, has been great. This trouble has varied in intensity, having 
been apparently most sever in 1910 and 1911. The distribution of these 
“brown spots” in any given piece of land is very erratic and the “brown 
spots” are often, one may say usually, sharply defined. Such consider¬ 
ations eliminate the waters, the alkalis and the neighboring lands as 
sources of the nitrates or of the nitrogen contained therein. In Bulletin 
155 of this Station, I suggested the atmosphere as the source of this 
nitrogen and fixation as the means of transferring it from the atmosphere 
