THE NITRIFYING EFFICIENCY OF CERTAIN COLORADO SOILS 
15 
Sample No. 84.—Another bearing orchard, probably fifteen to 
eighteen years old, in the same neighborhood as No. 83 gave us the next 
sample. The soil here is a heavy clay. When I visited the ranch in 
September, 1912, fifteen trees, all within a circular area in one corner of 
the orchard, were burning very badly. The foliage was practically all 
brown but the apples showed no signs of any injury and unless some 
very rapid change for the worse took place, they gave promise of ma¬ 
turing. In a remote corner of the orchard, three more trees were found 
to be buring. The soil between the trees showed no brown spots as 
yet, but the sides of the main ditch were brown four or five feet up 
from the water. My sample was taken near a burning tree and con¬ 
tained only a trace of nitric nitrogen and 128 p. p. m. of chlorin. Here 
also this orchard is to be looked upon as being in the incipient stage of 
the trouble. 
Sample No. 85 .—We have here another old orchard where the 
burning from excessive nitrates has been present, to our knowledge for 
four years, in 1910, the attack was very acute and about two and one- 
half acres of bearing trees were destroyed. Strangely enough, since 
then the onslaught has abated, and while a large number of the trees 
show the typical burning of the foliage, but few more have died. A con¬ 
siderable number are making practically no growth and are struggling 
along stunted and half leaved out. The soil is a clay loam and shortly 
after it is irrigated, the brown color can be seen very readily, developing 
along the irrigating furrows. The sample was taken in September, 
1912, near an affected tree and contained 6 p. p. m. of nitric nitrogen 
and 1000 p. p. m. of chlorin. The soil was very dry and hard at that 
time and no brown color was in evidence near where the sample was 
collected, although it had been seen in great abundance on other occa¬ 
sions. 
Sample No. 86 .—Sample No. 86 is a sandy loam and came from 
the mealy ridge of an irrigating furrow in an orchard where high ni¬ 
trates have made their appearance within the past three years. While 
collecting samples in this vicinity in former years, I had passed by this 
place many times but never until 1911 had I observed anything unusual 
about either the trees or the soil. The area of the orchard is about four 
acres, and in Ocober, 1911, every tree on the two acres was seriously 
affected, in fact, they were as good as dead. When I saw the place 
again in September, 1912, all of these trees had been grubbed out, and 
the two acres had been planted to oats and alfalfa. It goes without say¬ 
ing that the experiment had been disappointing. At least three-fifths 
of the trees on the remaining two acres were burning. A well defined 
crust had formed on a portion of the ground, and this was dark choco¬ 
late brown to black in color, all the darker because of its moist condition 
due to the presence of quantities of deliquescent magnesium nitrate, 
sample contained 130 p. p. m. of nitric nitrogen and 6400 p. p. m. of 
chlorin. 
Sample 87 .—This soil came from an orchard which was among the 
first to be called to our attention because of the heavy losses from high 
