tter in the soil more quickly available, an
increase in yield quickly following an application. These three effects
of burned lime brought it into favor, and a rational use would have
continued it in favor.

_Irrational Use._ The ability of caustic lime to improve the physical
condition of land and to make inert plant food available has led many
farmers to treat it as a substitute for manure, sods and commercial
fertilizers. Immoderate use gave increased crop yields for a time, and
the inference was easy that lime could displace the old sources of
plant food supplies. It became the custom in some regions to apply 200
to 300 bushels per acre to stiff limestone soils that had no lime
deficiency, as a test for acidity would have shown. The lime not only
made some mineral plant available, but it attacked the organic matter of
the soil, making it ready for immediate use and leaving the land
deficient in humus. Wherever stable manure and clover sods were not
freely used, the heavy application of caustic lime was followed
ultimately by decline in productive power. Such practice has come under
the condemnation of people who have not seen that the ill results have
no relation to the rational use of lime.

_What Lime Is._ There is abundant evidence that pulverized limestone, or
lime marl, or oystershell, or any other form of carbonate of lime,
corrects soil acidity and helps to make a soil productive. It is good,
no matter whether nature mixed the lime carbonate with clay, etc., to
make a choice limestone soil, or man applied it. Fresh burned lime is
only the stone after some worthless matter has been driven off by use of
heat. The limestone, carbonate of lime, is represented by the formula
CaCO_3. When heat is applied under right conditions the carbon dioxide,
CO_2, is driven off, and there remains CaO, which is calcium oxide,
called fresh burned lime.

If there were 100 pounds of the stone, and it was absolutely pure, 44
pounds would escape in form of the carbon dioxide, which had no value,
and 56 pounds would remain. The 56 pounds calcium oxide, or fresh burned
lime, have the same power to correct acidity as this same material had
when it was bound up in the 100 pounds of limestone. The 44 pounds were
driven off by heat, while if the limestone had not been burned the 44
would have separated from the 56 pounds in an acid soil, leaving the
actual lime to do the needed work of correcting acidity.

_Affecting Physical Conditio