IO 
Colorado Experiment Station 
Present Conditions in Regard to the Presence of Arsenic in the Soil. 
Several questions relative to this subject may be raised such as 
the presence of arsenic in soils in general. Toxicologists have an¬ 
swered this in the affirmative, but the evidence of all is that it is pres¬ 
ent in minute traces. This is not true of our Colorado virgin soils, 
for they contain more than mere traces, which question will be dis¬ 
cussed in a subsequent paragraph. The bearing of this fact on the 
question in hand is slight. The arsenic contained in the virgin soils 
examined, taken approximately to the depth of one foot, is just about 
one-tenth of the average found in the orchard soils, excluding extremely 
high ones. The maximum amount found in a virgin soil taken to a 
depth of one foot is almost exactly one-twenty-eighth of the maximum 
found in an orchard soil taken to the same depth. The orchardist is 
not concerned with the source of the arsenic but with its effect upon 
the trees. If there is already a little arsenic in some of our soils, 
enough to be taken up by the trees to such an extent that its presence 
may be shown, it does not argue that we do no damage by increasing 
this amount from io to 28 times. 
Another suggestion is that the water used for irrigating purposes 
may contain arsenic. It is a fact that some spring waters contain 
minute traces of arsenic, so small, however, that its presence may best 
be established by examining the deposits from such springs. It is, 
however, not true of our river waters, so far as my knowledge goes, 
and if it were true, the quantity usually carried by spring waters, not 
river water, is so small as to be utterly insignificant in comparison 
with the quantities which we have been pouring upon our lands. 
We have been using arsenical sprays in the various parts of our 
country for various purposes about 40 years. We, have been spraying 
our apple orchards about 28 years and in Colorado we have been spray¬ 
ing 18 or 20 years. The question is what has been the effect of this 
in regard to the amount of arsenic in the soil? The answer is given 
above,, i. e., that, even in Colorado, we have increased the arsenic con¬ 
tent of our orchard soils at least ten fold and in the older states it must 
be even worse if they have been nearly as zealous in spraying as we 
have been. But few people consider the real character of the sprays 
used and we cannot expect the ordinary orchardist to consider the pos¬ 
sible results and there has been an abuse of the practice. The prac¬ 
tice in this sense has been a dangerous one. I do not know that any 
station has ever advised six, eight or even nine sprayings in a season. 
Three is the maximum recommended by this station, and yet I know 
of men who have sprayed nine times in one season according to their 
own statements; four, five and six sprayings are still applied by some. 
The amount of arsenic used has also been unreasonable in many in¬ 
stances. I have in mind a man who, having been directed to use one 
pound of arsenious acid to the tank added one and a quarter pounds, 
and applied 90 gallons or a little over 0.56 pound of white arsenic 
to each tree during the season. I know another man who used al¬ 
most exactly the same quantity of spray, 90 gallons to the tree, using 
