Arsenical Poisoning of Fruit Trees. 
i i 
16 pounds of lead arsenate to the tank. This man claimed that this 
was his custom. Assuming this statement to be literally true, let us 
see how much arsenic acid he had applied to this orchard per acre in 
the six years preceding. As stated, he used 16 pounds of arsenate of 
lean to the tank and applied 90 gallons to each tree during the season. 
Assuming that the pasty arsenate of lead was one-half water it would 
give us eight pounds of dry arsenate of lead to the tank,0.04 pound 
in each gallon of spray and as he used 90 gallons to each tree he 
applied 3.60 pounds of dry lead arsenate, or if the dry lead arsenate 
contained 25% of arsenic acid, he added 0.9 of a pound of this acid 
to each tree or 72.0 pounds per acre each year counting 80 trees per 
acre. In six years he would add 432 pounds arsenic acid to each 
acre of his orchard, which if evenly distributed through the first foot 
of soil would give 108 parts per million. This calculation is much 
nearer to the facts in the case than such calculations are apt to be, 
for I found 61.33 and 128.83 parts arsenic acid per million in the 
upper portions of this soil. The other man who used 1.25 pounds 
white arsenic to the tank, said to me “you don’t realize how heavily 
I have sprayed. This ground was all white with it.” I do realize 
that he sprayed heavily, but he does not. He was adding arsenic 
acid to his soil at the rate of 51.84 pounds per acre per annum or 
taking it for a period of six years, as in the preceding case, he added 
310 pounds per acre, or 77.5 parts per million of soil. The latter of 
these men used 26 times and the former 36 times as much arsenic 
as we now know would have sufficed to have assured them a crop 
with not more than 5 per cent, wormy apples. These men have lost 
a number of trees from this cause. 
* 
The Amount of Arsenic Now Present in Our Soils. 
Determinations of arsenic in our orchard soils have indicated the 
following range; 25.5, 26.0, 30.6, 36.8, 38.2, 39.9, 61.3, 128.83, ana 
137.99 parts arsenic acid per million. The samples were taken, some 
from about the base of the tree and others out under the heads of 
the trees and to depths varying from four inches to one foot. The 
soils here represented are without exception desirable ones, they are 
free from seepage and alkali, and are well supplied with water. 
These orchards receive good care, still there is more or less of the 
trouble described as arsenical poisoning in each of them and some of 
them are very badly affected. 
That the arsenic should accumulate in the soils is what we would 
expect. The materials used as sprays are not very soluble in water. 
The amount of water applied to our soils is not excessive, irrigation 
waters and rainfall together amounting to not more than 24 inches. 
The materials are not volatile and the evolution of arseniureted hy¬ 
drogen from the soil has not yet been proven, though a slight elimina¬ 
tion of the arsenic in this form, especially under favorable condi¬ 
tions, might take place.* The fact, however, is exactly what we would 
