LaMotte CALCIUM & CHLORIDE MODULE A - Manual (Page 3)

INTERPRETATION OF REPLACEABLE CALCIUM TEST RESULTS
A lack of calcium in the soil rarely limits plant growth, but it helps to provide a
favorable equilibrium between the various constituents in the soil which affect fertility.
If there is a defi ciency in the replaceable calcium in the soil, the base exchange
capacity is incompletely satisfi ed, resulting in acid soil. Valuable biological processes
are dependent upon the important stabilizing effect of calcium in the soil, and without
its benefi cial effects the nitrifi cation process would bring about a highly injurious acid
condition.
Well-limed soils, those that are not naturally in need of lime, contain an abundance
of replaceable calcium. Hence, this test can be used to confi rm and supplement the
interpretation of soil acidity measurements.
The amounts of calcium that are extracted from soil by the leaching solution provide
a measure of the amount of calcium contained in the base exchange complex. Soils
low in humus and clay give higher values than soils that have a high percentage of
colliodal clay and organic matter, unless the latter are strongly acid and, consequently,
have most of their calcium replaced by hydrogen-ions.
Normal sandy soils should give 500 ppm calcium; clay soils 1000 ppm; and humus
soils, such as peats and forest mold, 500 ppm. Lower results indicate that much of the
active calcium of the soil has been replaced by hydrogen or other ions, as in acid or
highly alkaline soils.