8 
Colorado Experiment Station 
telligently cultivated, and well located in respect to protection against 
severe weather and yet this trouble was exceedingly prevalent, while in 
other orchards on less desirable, even on bad soil, this trouble, though 
present, was by no means so prevalent. In otheE cases the problems 
presented were so involved that no student of this subject would under¬ 
take to unravel them. I am fully convinced that the soil itself does 
not produce the trouble under discussion. 
Do Salts Other Than Arsenic Produce It? 
The answer is a negative one. We have very marked cases of 
trees having been killed by the presence of excessive amounts of ni¬ 
trates formed in the soils. I described some of these at the meeting 
of the Society for the Promotion of Agricultural Science in Portland, 
Oregon in August, 1909,. The action of the nitrates is wholly differ¬ 
ent from that of the arsenic, neither the crown nor the roots are cor¬ 
roded but the foliage and the tree are killed outright, sometimes with¬ 
in a few days. The attack expresses itself wholly differently, it is not 
gradual, but as above stated sudden, there is no ripening of the foilage 
but a strong burning and killing. The bark of the crown and the large 
roots at the time of the attack is perfecly normal in appearance in 
cases not complicated by pre-existing troubles. 
I have found no conditions under which any trouble can properly 
be attributed to the presence of any excess of sodic ehlorid. I have 
endeavored to determine the effect of sodic ehlorid by direct experi¬ 
ment. It is beyond question that salt, in excessive quantities, is injuri¬ 
ous to apple trees, but excessive quantities, according to our rerults, 
would mean very many times as much salt as we find in any of our 
soils. Its action was very moderate and expressed its only visible ef¬ 
fect upon the leaves much in the same manner as the nitrate. 
There is no carbonate of soda, worthy of mention, in our soils, 
so the action of this salt is eliminated from the question. 
There is in some cases a rather large amount of sulfates (sodic, 
calcic, and magnesic) present but the action of these is not corrosive. 
Their action is so mild that seedling plants grew in soils to which I 
had added as much as two per cent, of the weight of dry soil of sodic 
sulfate and even the little seedlings were not corroded or injuriously 
affected. I have made a similar experiment with magnesic sulfate. 
These experiments were made years ago when the opinion prevailed 
that the alkalis were prejudicial to our lands. These experiments are 
in keeping with the fact of common observation in many parts of the 
state, i. e., the production of good crops on lands so rich in alkalis that 
a heavy incrustation covers them under conditions favorable to its for¬ 
mation. I know of very healthy orchards on land rich in these salts. 
Is the Trouble Produced by Excess of Water? 
This question is likewise to be answered in the negative. We 
know that we can destroy even pear trees by keeping their roots sub- 
