Re: lime, soils, solubility

As pointed out in several posts, not all soils are the same, nor are all forms
of lime.

The mention of slaked lime sat me upright with a jost.  I would *never* use
slaked lime in a garden if I cared about what was growing there.  Slaked lime
is Calcium hydroxide, made from limestone heated in water,  but by no means
equivalent to it.  It is so strongly alkaline it burns--badly.  Any organic
material will be attacked by it and destroyed.  As a "fast fix" for applying
Ca to a soil it may have the desired effect all right, but will have such
serious deleterious side effects to the organic fraction--all the way from
microflora and fauna as well as more visible living things *and* the very
valuable organic residue (compost and such)--as to render the soil in worse
condition than it was before the application.

Lime itself is gentle, chemically.  It is practically insoluble--as witness
massive limestone cliffs in large canyons.  In gardens, the limestone is
"soluble" to such a limited degree that it is automatically "timed release."
The more finely divided the lime, the more quickly it is incorporated.
Granulated or pelletized lime has been treated so that it has a structure
readily penetrated by moisture. It is perhaps even more available than the
powdered form which has a tendency to clump into a solid mass, remaining
visible for months as undissolved, undispersed masses in the soil.

Gypsum is also very slightly soluable, but has some beneficial effects in some
soils that straight lime does not because of the release of both Ca and
sulfate ions into the soil mix.

Chemical forms that contain Magnesium may be more available initially, but the
Mg is so highly soluble that it leaches out of the root zone in very short
order unless adsorbed by clay--*adsorbed* meaning grabbed onto and bonded
chemically to the clay platelets.  Adsorbed ions are of very limited, but
real, availability to plants, incidentally.

One must be patient and consistent in the application of any form of lime to a
soil.  The effects accumulate from year to year.  This year's application may
be three or more years from peak effect.  That is one reason this is a
procedure needed to be repeated year after year.

Neil Mogensen  z 7 near Asheville in the mountains of western NC

---------------------------------------------------------------------
To sign-off this list, send email to majordomo@hort.net with the
message text UNSUBSCRIBE IRIS
Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index