20 
COLORADO EXPERIMENT STATION 
furrows. A short distance away I found about a dozen apple trees 
badly burned so 'that my diagnosis of the condition of the soil was coo- 
firmed. 
In 1911 I visited the orchard and again in the fall of 1912, but on 
both occasions I failed to find either the brown color on the soil or 
burning of the apple foliage. The peach trees were yielding well and 
everything seemed to be normal. I took a sample of the soil, a heavy 
clay, however, as typical of our best peach land and have regarded it as a 
normal soil. It contained 4 p. p. m. of nitric nitrogen and 120 p. p. m. 
of chlorin. 
Sample No. 94 .—A short distance from the orchard described 
as No. 93 is a large apple orchard where in 1910 six acres 
of bearing trees were killed and in 1911 ten acres more were 
so nearly exterminated that the owner grubbed out all of the sixteen 
acres. Peaches were set out where the apples were removed and when 
I saw them in September of 1912 they seemed to be thriving. At this 
time the soil was moist from a recent irrigation and it was brown every¬ 
where, particularly on the sides and crests of the irrigating furrows. 
Although this condition prevailed in the remainder of the apple orchard, 
I was able to find only one tree that was burning. In all probability the 
nitrates either had not become sufficiently concentrated as yet or they 
had not been washed down to the zone of the feeding roots. My sample 
was taken from the ridges of three irrigating furrows and included the 
top four inches. It contained 34 p. p. m. of nitric nitrogen and 420 
p. p. m. of chlorin. 
Sample No. 95.—This sample consisted of the brown surface half¬ 
inch form the irrigating furrows described in the preceding sample. The 
color varied from the brown of iron rust to dark chocolate. The soil 
was quite moist and there was no mealy condition beneath the surface 
crust. It contained 600 p. p. m. of nitric nitrogen and 150 p. p. m. of 
chlorin. My purpose in taking this sample was to compare the nitrify¬ 
ing efficiency of the surface crust where the nitrates had become con¬ 
centrated with Ihat of soil from the same source taken to greater depths. 
Sample No. 96 .—The next sample came from a peach orchard 
where the owner complained of the peach leaves turning yellow and 
the immature fruit dropping. We have never had an opportunity to 
observe the behavior of bearing peach trees when grown where nitrates 
are excessive and consequently we did not know just what to expect. 
So far as our records go, they show that both pears and peaches with¬ 
stand niter very well. This soil was a nice sandy loam; it exhibited no 
brown color, and, as a subsequent chemical determination showed, the 
nitrates were not excessive, although somewhat higher than other soils 
in that vicinity. We have no reason for thinking that the peach trouble 
metioned above was caused by the small amount of nitrates present. 
The sample was collected near one of the affected trees and contained 
20 p. p. m. of nitric nitrogen and 170 p. p. m. of chlorin. 
Sample No. 97.—The next sample came from an apple orchard in 
