Alkalis In Colorado 
5 
TERM “ALKALI” USED IN COLLOQUIAL SENSE 
The term “alkali" is used in its colloquial senes whenever reference 
is made to such a mixture of salts as has been described. The sulfates 
of lime and magnesia are not alkalis in a proper sense and it is a ques¬ 
tion, how far we should consider calcic sulfate an alkali, even in this 
colloquial sense. The reasons why we consider its use doubtful are: 
First, it is in no case injurious to general crops, on the contrary it is 
often applied to land as a manure, something to do the land good. 
Second, it constitutes such a large percentage of a few soils which are 
often quite productive that we are justified in neglecting it among the 
alkalis which we consider accidental soil constituents peculiar to semi- 
arid regions, remaining in the soil because there has not been a suffi¬ 
cient rainfall to wash them into the rivers. The sulfate of lime, how¬ 
ever, that fairly forms a zone along the eastern flank of the Rocky 
Mountains has not so simple a history and could not readily be removed 
by any conceivable rainfall. On the other hand, this salt actually forms 
a part of the mass of efflorescent salts to which the popular name 
“alkali” is applied and makes up a large percentage of these salts, 
sometimes almost the whole of the efflorescence. We cannot well re¬ 
ject such efflorescences from the group of our popularly designated 
alkalis. This difficulty does not attach itself to the sulfate of magnesia 
though, chemically, it has a close family relation to the calcic sulfate. 
These salts, singly and in sufficient quantities, are injurious to 
vegetation. Many apple orchards in Colorado have unwisely been 
planted on land under-laid by gypsum (often shortened to gyp.), at 
shallow depths. Such orchards grow for a few years and then turn 
yellow, because unthrifty, and perhaps die. This is an experience alto¬ 
gether too common in Colorado. The yellow, unthrifty condition of 
such orchards, and in some cases the death of the trees, is attributed 
to the action of the gypsum. If this view be correct, then the calcic 
sulfate should be included among the injurious salts. Though this 
view seems well sustained by observable facts it is not so simple, for 
the gypsum, which is of frequent occurrence almost as a hard-pan quite 
near the surface in many sections, is not pure gypsum. I have found 
much of it quite rich in arsenic, which may in part or even wholly ac¬ 
count for the unhealthiness of the trees. 
It has been often observed that apple trees planted on gypsum 
lands bleed from wounds, especially during the second year after trim¬ 
ming. This bleeding causes the deposition of a light brown deposit, 
often forming pendant masses several inches long. These deposits are 
rich in lime and arsenic. This bleeding, with its resultant deposits is 
abnormal and such quantities of lime and the arsenic are not proper 
constituents of the sap of the apple tree. It looks as though the gyp¬ 
sum, with its arsenic, were the source of this trouble. This does not 
