46 
Colorado Experiment 'Station 
surface foot of soil taken at the place from which a dead tree had been 
removed. The determination of the water soluble portion, 0.22 
per cent, does not indicate an excess of soluble salts. The history 
of this land shows that it is productive. A portion of it was at one 
time used as a vegetable or truck garden and produced well. The 
suggestion that the truck garden might have been heavily fertilized 
and thus forced into productiveness suggested itself at once and I 
urged it. The answer was the trees then should show where the truck 
garden was but they are neither better nor worse than in other portions 
adiacent to it. 
We have no proof that starvation due to the infertility of the 
soil does in any measure account for the present conditions of the 
trees. 
Another question somewhat more serious than the preceding 
is in regard to the presence of other poisonous substances besides 
those of the spray materials. This includes lead and copper. 
There is only one present which might possibly exercise a deleterious 
influence and that is lime. I have pointed out elsewhere that apple 
trees do well in limestone soils, at least they do not show the distress 
exhibited by the trees under consideration. We have no justification 
in fact, so far as I know, for assuming that lime as carbonate is in¬ 
jurious to apple trees and still less ground to assume that lime as a 
silicate is injurious, but a casual inspection of our analysis shows 
that the lime was probably present in both of these forms and possibly 
to a slight extent as sulphate. 
So far neither the analysis of the soil nor the information re¬ 
ceived in regard to the garden crops grown give us the least reason 
for attributing the condition of the orchard to the infertility of the soil 
nor to any poisonous substances other than the spray materials or 
possibly to the simultaneous action of arsenic and lime, as has been 
pointed out under the latter subject. 
The depth of the soil has been stated as given to me, but I doubt 
whether the soil is quite so deep as three to three and a half feet. 
I dug down to the, bottom of the soil at some points and found it 
about two feet and then a marly subsoil. 
I think it safe to assume that there is not lime enough in the soil 
to do any harm; further, I think it safe to assume that the denth 
of -the soil is amply sufficient to grow healthy trees, provided that 
the subsoil is not in some way injurious. 
I have tried to find out what is probably the greatest denth at 
which our apple trees feed, and judging by the depth at which I have 
found the fibrous roots under what I considered the most favorable 
conditions I would judge that depth not to exceed two and one-half 
feet. This depth of soil, then, would ordinarily be ample and I believe 
it is. If this be correct, the character of the subsoil lying below 
this depth, provided it was pervious to water, would probably not be 
of as great importance as we, at first glance, might think, for even 
if it contains arsenic, and I have strong reasons for believing that it 
does, this arsenic is at best difficulty soluble in water and lies below 
