12 
Colorado Experiment Station 
Injure Vegetation If Present In Large Quantities 
These salts, included under the general term “alkali” are all in¬ 
jurious to vegetation when present in large enough quantities, which 
of course, vary for different plants and for the different salts. Our in¬ 
formation relative to the amount of these indiivdual salts which may 
be required to do damage to the crops is not very satisfactory and this 
is not surprising, as we cannot imitate, or even determine, all of the con¬ 
ditions which may be met with in our fields. I think that it can be 
safely stated that the most dangerous salts that we have mentioned 
are the nitrates. I do not know that there is any distinction to be 
made between the different nitrates that we have mentioned, calcic* 
magnesic, and sodic nitrates. They are all very soluble and all pois¬ 
onous when present in large quantities. How they act upon the plant 
I do not know, but the results that they produce are very marked and 
they cause the death of the plants very quickly. The plants that I 
experimented with were 4-year-old apple trees. I know how much 
nitrate of soda I put on the ground and to how large an area I applied 
it, but I don’t know how strong the solution was that reached the 
feeding roots nor do I know what proportion of the feeding roots of 
the trees were reachel. My object in the experiment was to see what 
the effects of the nitrates were upon apple trees and not to determine 
the points that have just been mentioned. Further, I don’t know how 
the effects were produced, whether by absorption, the prevention of 
osmosis, or whether the solution to all intents and purposes simply 
killed the root hairs. This much I do know, i.e., the leaves burned and 
the trees died, or were badly injured. One of these trees was dead 
in four days after the application of the nitrate. It was left standing 
for two years but it never recovered. I have seen old trees with per¬ 
fect foliage and a full crop of half-grown fruit burn and die in a few 
days and I have never seen an instance of recovery in trees injured in 
this way. Sometimes only a part of a tree may be injured and this 
injured part dies. I have dug up such trees and followed the roots 
for as much as 27 feet from the trunk in an endeavor to find how the 
nitrates killed the tree. I have never been able to determine this. In 
the four-year-old trees experimented with I was unable to find any 
nitric-nitrogen in the leaves in more than traces although I had firmly 
expected to find it. Some plants, heliotropes, from the greenhouse 
treated with saltpetre were placed at my disposal; in these cases there 
was no trouble in finding nitrates in the leaves, for the nitrate crystal- 
ized out on their surfaces. We are not sure that the two cases are 
parallel but the important end results were the same—the plants were 
killed. I am inclined to think that the action of the nitrate in these 
two cases was different in character. In the case of the apple trees I 
think that the burning of the leaves was due to drying out caused by 
