i 8 
Colorado Experiment Station 
presence of sodic sulfate in our soils, in the quantities in which we find 
it, is scarcely objectionable at all. 
Sodic chlorid is much less injurious than sodic sulfate and its 
action is lessened by the presence of other salts, notably so by calcic 
carbonate. The presence of calcic carbonate reduces the action of 
sodic chlorid to one-third of the action it shows when calcic carbonate 
is absent. 
NITRATES AND CARBONATE OF SODA DO GREATEST DAMAGE 
The two salts that we meet with in the alkalis in Colorado which 
have done us serious damage are the nitrates (calcic, magnesic, and 
sodic) and the carbonate of soda. 
EFFECTS OF SODIC CARBONATE 
It is difficult to tell which of these two classes, the nitrates or the 
soluble carbonate, especially sodic icarbonate, has done us the greater 
damage, but probably the nitrates, for these have a very wide dis¬ 
tribution and are very poisonous even in comparatively small quan¬ 
tities, but how small these quantities may be I do not know. The 
sodic carbonate is likewise injurious in quite small quantities but in 
this case we have a pretty definite idea of how much may be present 
in the soil before it becomes dangerous to the plants. The amount in 
the soil that will injure wheat plants amounts to 0.04 percent of the 
soil, while beet plants will endure it up to 0.05 percent. It is, how¬ 
ever, doubtful whether beet plants will live and produce beets with so 
much as 0.05 percent of sodic carbonate or “black alkali”, in the soil. 
These two figures probably represent the largest amounts that may be 
be present without injury to the plants. These percentages mean, 
when put into pounds, for instance, that 100,000 pounds of soil may 
contain from 40 to 50, or i,000,000 pounds of soil may contain from 
400 to 500 pounds of sodic carbonate before it will actually kill the 
plants. A smaller quantity may cause the ground to bake very badly 
and in this way interfere with the growing of a crop. The figures 
given above amount to from 1,600 to 2,000 pounds of sodic carbonate 
to the acre-foot of soil, but a much smaller quantitv than i,6co pounds 
to the acre-foot may be sufficient to do damage if it be concentrated 
in the upper part of the soil. I suppose that, as a rule, we plant our 
small seed, wheat for instance, from 2 to 2^ inches deep. If the sodic 
carbonate in the top 3 inches of the soil, or at any point in the top 
3 inches of this soil, equals or exceeds 0.04 percent of the soil, it is 
apt to kill the young plant? This statement leaves out the danger of 
the baking of the soil which may be caused by a much smaller amount 
of this salt. 1 don’t know how small an amount of sodic carbonate it 
takes to cause the soil to bake on drying, but a sample of a sandy soil 
which I gathered for the purpose of determining the sodic carbonate 
