five, or six years, and, wherever lime is cheap, the unpleasant
character of the labor inclines one to make the application in
sufficient amount to last through two such rotations. It is a
reasonable assumption, however, that more waste results from the
heavier applications at long intervals than from light applications at
short intervals. In any event need will return, and soil acidity will
again limit income if applications do not continue to be made.

CHAPTER III

APPLYING LIME

Forms of Lime.--There is unnecessary confusion in the mind of the
public regarding the forms of lime that should be used. If amounts
greatly in excess of needs were being applied, the form would be a
matter of concern. There would arise the question of soil injury that
might result from the use of the lime in caustic form. Again, if
pulverized limestone were used, a very heavy application would bring up
the question of coarseness in order that waste by leaching might be
escaped. Most farms needing lime do not have cheap supplies, and the
consideration is to secure soil alkalinity at a cost that will not be
excessive. Freight rates and the cost of hauling to the fields, added
to first cost of the lime, limit applications on most farms to the
necessities of a single crop-rotation which includes clover, or, at the
most, to two crop-rotations. Under these circumstances it is best to
let cost of correction of soil acidity determine the form of lime to be
used.

The material that will render the soil friendly to clover for the least
money is the right one to select. We need to be concerned only with the
relative efficiencies of the various forms of lime, as measured in
terms of money. That which will most cheaply restore heavy clover
growths to the land is the form of lime to be desired. The contentions
of salesmen may well be disregarded as they produce confusion and delay
a work that is important to the farmer.

Definitions.--The use of the various forms of lime will become general,
and the terms employed to designate them should be understood. They
vary in their content of acid-correcting material, and their correct
names should be used with accuracy.

_Stone-lime_, often called lump-lime or unslaked lime, or calcium oxide
or CaO, is a form widely known, and may be taken as a standard. It is
the ordinary lime of commerce, and is obtained by the burning of
limestone. One hundred pounds of pure limestone will produce 56 pounds
of