THE NITRIFYING EFFICIENCY OF CERTAIN COLORADO SOILS 
17 
1912, when the last trees died, the brown color covered the entire area, 
spreading, in more or less broken stretches, over the ground occupied 
by the very outside tree-row. The soil in the beginning was a rather 
heavy clay loam; now it is quite mealy and ashy in character. 
I do not know where we could find a better illustration of the 
formation and spread of nitrates from a central point than is given in 
this case by the regular succession in which row after row of trees 
went down before the approaching niter wave. 
One rather interesting thing that occurred in connection with this 
soil was the very luxuriant growth of salt bush which took place in the 
summer of 1911. With the exception of a few barren spots, here and 
there, where the nitrates were evidently too concentrated, the whole 
forty acres were covered with this weed, waist high. During the pre¬ 
ceding three years, nothing had grown there, but the winter and spring 
of 1911-1912, were very wet for this locality and it is possible that the 
nitrates were washed out sufficiently to allow the Atriplex to become 
established. While there were some weeds here in 1912, the vigor of 
the growth and the area covered were nothing compared with that of 
the preceding year. The tract was entirely barren in 1913. 
My sample was taken between the two living trees that had just 
been cut, where the soil was beginning to get rather mealy. It con¬ 
sisted of the surface-three inches and contained 70 p. p. m. of nitric 
nitrogen and 8300 p. p. m. of chlorin. 
Sample No. 89 .—The sample was collected from an orchard where 
the trees have been dying since 1908. The owner believed that the cause 
of the trouble was starvation so he gave the soil a heavy dressing of 
stable manure, thereby, in all probability, aggravating the attack. At 
any rate, no benefit whatsoever resulted, and year after year more and 
more trees have succumbed until about three and one-half acres died 
and were grubbed out. One year the land was planted to spring wheat 
where the trees were removed, but practically none of it ever came 
through the ground. When I last saw the place in the fall of 1912, the 
burning had extended north and west into the good part of the orchard 
five more rows, but there was almost none to be found in the remain¬ 
ing five or six acres. The ground appeared to have been heavily ma¬ 
nured quite recently. The soil was a coffee-brown color where the 
trees had been taken out, and no attempt was being made to use the 
land. It was not wet and there was no water in a test well at a depth 
of 6 feet, although spots of white alkali were showing up here and there. 
The soil is a sandy loam, not particularly mealy. The brown color had 
not yet developed, at least it was not visible at that time, where the 
trees were then burning and where I took my sample. Nitric nitrogen 
amounting to 180 p. p. m. and chlorin to 1600 p. p. m. were found. 
Sample No. 90 .—We have next the case of a ninety acre apple 
orchard where the trees commenced dying from too much nitrate in 
1908. At this time the brown stain was most conspicuous on the sides 
of the irrigating furrows, but more recently it has spread over the en¬ 
tire surface in some parts of the orchard. During 1910-1911 the vio- 
