12 
COLORADO EXPERIMENT STATION 
possession of practically the entire area. Evidently the nitrates had 
been reduced by the heavy rains of the preceding winter and spring to a 
point of tolerance for these weeds since in other years nothing of this 
kind had occurred. I do not know what crop, if any, occupied the 
land in 1912, but when the present sample was collected in May, 1913, 
it had been sown to oats. The stand was exceedingly thin and the 
bulk of the growth was confined to the narrow zone adjacant to the 
irrigating furrows. Between these, the plants were very scattering. 
There was considerable white alkali in evidence, and the sides of 
the irrigating furrows bore a slight crust beneath which the soil was 
mealy. There were no well defined brown or chocolate colored areas 
as in previous years, but the whole field presented a marked brown¬ 
ish aspect. The soil is a clay loam and contained nitric nitrogen at the 
rate of 26 p. p. m. and chlorin 4,500 p. p. m. 
Sample No. 78 .—While our chief interest in this investigation at¬ 
tached itself to cultivated soils, we have selected, nevertheless, one 
sample from the side of an adobe hill where the soil was just being 
formed from the weathering shales. This was raw land, of course, 
if it could be styled land at all, and there was no evidence that any¬ 
thing had ever grown upon it. The overlying mesa was in cultivation, 
and judging from the water erosion of the hillside, it had received some 
of the leachings from above during heavy rains. Such formations as 
this, by gradual weathering, are contributing quite extensively to 
the formation of our heavy adobe clay soils and it was of considerable 
interest to learn whether the ancestors of these soils were as active 
biologically as their cultivated offspring. There was no white alkali 
visible on the surface and no seep from the side of the hill at the time 
the sample was taken, May 13, 1913. The nitric nitrogen was higher 
than I should have expected had it not been for the wash from above; it 
amounted to 140 p. p. m. and the chlorin to 700 p. p. m. 
Sample No. 79.—The next sample came from a well drained 
orchard where there was uever any white alkali to be seen, but where 
the niter trouble has been manifesting itself to a greater or less degree 
for the past four years. When it first made its appearance it was con¬ 
fined to a few rows of trees on the west side of the orchard; today, 
it extends up and down both sides of the main highway for several 
miles, easily recognized by the dark brown, greasy appearance of the 
soil. That section of the orchard from which this sample was taken 
is a red clay loam, and owing to this color it has always been difficult 
to discern any decided brown discoloration, although in another part 
where the formation is different, the brown color is strongly developed. 
In 1910, the burning was very moderate and there seemed little 
reason for anticipating any grave danger from this cause. A few 
trees had died, but most of those affected appeared to be dying slowly 
rather than to be going in one season as is often the case. The next 
year, the number involved was considerably greater and the burning 
continued to be relatively mild, but by 1913, although the disaster had 
been moving slowly, it had been accomplishing its work just as surely, 
