THE NITRIFYING EFFICIENCY OF CERTAIN COLORADO SOILS 
19 
At no time have I observed any brown color on this soil. The 
present sample, a heavy clay, was taken from the two and a half acres 
described above and contained only a trace of nitric nitrogen and oO 
p. p. m. of chlorin. 
Sample No. 92 .—This soil came from an orchard which is very 
favorably located for securing the best possible natural drainage. It 
borders on a river and is about twelve feet above the ‘normal level of 
the stream. The soil is a light sandy loam and is underlaid at five 
to eight feet with coarse gravel. When the river is at flood, the level 
of the ground-water has been within ten inches of the surface and in 
the depressions the water has stood two inches deep so there can be no 
question about the openness of the soil. It has been frequently ob¬ 
served on this place that the ground water rises and falls regularly 
with any appreciable change in the level of the river. 
The orchard is about twenty years old and until 1909 it had been 
very productive. During that year, the brown color became very con¬ 
spicuous on the surface and the nitrates developed very rapidly. Ap¬ 
proximately three hundred apple trees were killed, and in the spring 
of 1910, they were removed. The entire surface of four and one- 
half acres from, which the trees had been taken was covered with a 
hard brown crust beneath which the soil was mealy and ashy. Corn 
was planted here, but it amounted to nothing since much of it never 
came up, and what little succeeded in getting through the ground turn¬ 
ed yellow and died when it was 8 to 10 inches high. Not despairing of 
all hope, the owner planted it to cantaloupes in 1911. Here and there 
a plant got established and produced very well, but the crop as a whole 
was a dismal failure. The tract was sown to.oats in 1912 but only those 
plants that were next to the water in the irrigating furrows survived. 
A good many got to be six to eight inches tall and then burned. In 
some places weeds were growing in the furrows, but in many others 
neither weeds nor oats could endure the nitrates and the stand was so 
poor that it was not considered worth irrigating. When I visited the 
ranch in the fall of 1912, the burning had extended no farther into the 
orchard than in 1911 and had stopped abruptly almost to the row. 
Strangely enough, there wefe a few scattering trees next to the river 
that were badly burned. One tree in particular attracted my attention, 
since it was not to exceed ten feeit from the edge of the river bank and 
twelve feet above the water, yet it was as brown as could be from niter 
injury. Most certainly the burned condition of the leaves could not be 
attributed to poor drainage in this case. 
My sample was collected from, the barren area and contained 320 
p. p. m. of nitric nitrogen with 7800 p. p. m. of chlorin. 
Sample No. 93 .—Thus far, all of the orchards which we have de¬ 
scribed have been apple, but we come now to a section of the country 
where peaches and apples are grown in alternate rows, the peaches be¬ 
ing used as fillers. I first became interested in this orchard in 1910, not 
because of the niter but because of a peculiar physiological condition 
of some apricot trees. While looking about for some explanation of 
this trouble I noticed the same brown color on the sides of the irrigating 
