49 
EFFECT OF CARBON BISULPHID ON THE 
YIELD OF CROPS. 
A. GIRARD. 
[From Vol. VI, No. 6, Experiment Station Record.] 
In view of the increasing use of bisulfide of carbon for the 
destruction of subterranean insects, as root lice, root maggots, 
white grubs, ants in their nests, etc., a knowledge of the effects 
of this substance on soils and vegetation becomes important. 
That it will destroy plant life when used excessively is abund- 
antly proven, with the phylloxera of the grape of Europe. In 
the first experiment with this substance vines were frequently 
killed by overdosing, and the treatment d’extinction, as em- 
ployed in Switzerland and some other European countries out- 
side of France, consists of using it in such quantities that the 
infested vines and lice are destroyed at the same time. L. O. 
Howard states that in an experience of his in destroying an ant 
nest the grass immediately surrounding was killed. With these 
facts in mind it is interesting to note that this substance seems 
to have a strikingly beneficial effect on the soil in greatly 
increasing its fertility. This seems to be conclusively shown in 
an elaborate series of experiments conducted by the author and 
extending over a number of years. Attention was first called 
to this action by the results following an attempt to destroy a 
mematode (Heterodera schachtii) upon the roots of the sugar 
beet. To kill the parasite, protected as it was in the substance 
of the beet, it was necessary to use the bisulfide at the rate of 
9 V 2 oz. to the square yard, or 2,904 lbs. to the acre, which result- 
ed in the complete sacrifice of the beet crop. Wheat grown on 
the same field the year following, however, exhibited a remarka- 
ble superiority throughout the tract treated with the insecticide, 
and this led in the following years to a series of trials at the 
same rate. 
The results the second year after the original treatment, 
without further additions of the bisulfide or use of fertilizers, 
were as marked as in the first year’s crops. The explanation 
of this increased vigor of plant growth is not altogether satisfac- 
tory. It is supposed that the bisulfide acts as a stimulant to 
vegetation and also poisons subterranean insects or other organ- 
isms, crypto gramic, perhaps, which otherwise would injuriously 
affect the roots of plants. It may also exert some chemical 
action on the soil elements, resulting in their easier assimilation 
by plants. 
These results, with accompanying explanations, are in con- 
trast with, but not necessarily contradictory to, the commonly 
held idea that the use of bisulfide of carbon is liable to stop the 
nitrification or conversion into plant food of the vegetable 
matters in the soil by destroying the microscopic germs which 
bring this about. But this experiment indicates, at least, that 
benefit rather than injury to the soil in its productive capacity 
is to be anticipated where the substance is employed in the 
ordinary application in vineyards, or at about one-tenth the rate 
given above, viz.: a little less than 1 oz. to the square yard, or 
290 lbs. to the acre, with a minimum rate of 175 lbs. to the acre. 
