one neutralizes the other. This test with litmus paper is a test for
soil acidity, and the fact that the moisture of the soil has turned
the litmus from blue to red shows that this soil is acid, or sour.
The soil moisture contained enough acid to neutralize the trace of
alkali contained in the blue paper and to change the paper to a
distinctly light red color; and the fact that the paper remains red
even after drying, shows that the soil contains fixed acids or acid
salts, and not merely carbonic acid, which if present would
completely volatilize as the paper dries.

"Now, these two tests are in harmony. The one shows the absence of
limestone, and the other shows the presence of acidity, and
consequently the need of limestone to correct or neutralize the
acidity, for limestone itself is an alkali."

"But limestone soils are not alkali soils, are they?" asked Mr.
West.

"Not in the sense of containing injurious alkali, like sodium
carbonate, the compound which is found in the 'black alkali' lands
of the arid regions of the far West; but chemically considered
limestone is truly an alkali; and, as such, it has power to
neutralze this soil acidity."

"Is the acidity harmful to the crops?"

"It is not particularly harmful to the common crops of the grass
family, such as wheat, corn, oats, and timothy; but some of the most
valuable crops for soil improvement will not thrive on acid soils.
This is especially true of clover and alfalfa."