38 The Colorado Experiment,Station. 
The water-soluble in this sample equalled 8.590 percent and the 
nitrates equaled 44.0 percent of this, or 3.78 percent of the sample 
as it was .gathered, showing that the surface soil is now very, rich in 
nitrates. Sample No. 1061 is an actual sample of this soil taken to 
a depth of from four to six inches; the sample is a composite one 
from ten different points in the field. We see that it contains 
practically 1.5 percent of the water-soluble salts of which 13.0 
percent was sodic nitrate which gives us 3,900 pounds of nitrates 
in the top six inches of the soil. This land lies on and above the 
wash alluded to which is eleven feet ten inches deep and is actually 
encroaching upon this land on both the north and west sides, 
which ought to secure excellent drainage especially as the land is 
not a heavy adobe soil, still it will puddle and retain water more 
persistently than one would think. The presence of the nitric acid 
in the first sample of soil, No. 815, taken at the base of one of 
these trees was a surprise to me, though I knew of its occurrence in 
adjoining portions of the land where the trees had already died. 
This whole section of trees, probably ten acres, has been dug up. 
It is useless to attempt to present to oneself any questions in 
regard to what would have been the condition of this orchard and 
land had it not been drained, as it was a little over ten years ago. I 
am satisfied that the drainage system carries off the excessive 
water whether it is from the irrigation applied or from other 
sources and establishes a zone and certain areas where there is a 
comparatively uniform and moderate, but still an abundant supply 
of moisture which renders possible the development of the nitrates, 
if other conditions are favorable. What the optimum degree of 
moisture may be I do not know but my observation leads me to 
believe that a constant supply amounting, near the surface, to 18 
or 20 percent, is sufficient for a rapid development of the trouble. 
After this is thoroughly established it seems to modify the moisture 
conditions of the soil as has been indicated by direct assertion of this 
fact and further by describing the ground as a veritable mud. 
Orchard No. 14 is also a large orchard, but has quite a dif¬ 
ferent soil. The burning has been very general and serious, at 
least twenty acres being involved, some of it on rather high and 
sloping land, some of it on lower and level land. The develop¬ 
ments in this orchard during the season of 1910 were sufficient to 
cause the manager and the owners the gravest anxiety, while the 
developments in the past month, May, 1911, are extremely serious. 
In this case we probably have an illustration of the effect of 
the irrigating water washing the nitrates down into the feeding 
area of the roots, and thus causing the damage, for some of the 
soil, while it is stained brown, is not at all in a bad condition. 
The former manager of this property kept the orchard well culti¬ 
vated and the soil was in fine condition throughout the season of 
