RE: Let's try this...is veddy veddy interesting...

List,

Wow, I saw this exact same "tract" (below) a few years ago from a
local nursery, except that, 1) the author was different, and
2) everywhere it says "western colorado", it said "south-east
idaho". Hmmm.... something fishy goin' on...

But, this tries to make the point that you don't add gypsum to
lower pH. WE ALREADY KNOW THAT. What we need to remember
is that we want is to diminish excess magnesium and potassium.
That is what the gypsum is for. Did I get that right?

Anyway, thanks for sharing. I've already added my gypsum and
sulfur (my patch is bare) so that will have to be my story and I'm
sticking to it.

Regards, Cliff in Belgium (this week only!)





ALKALINE SOILS
AND THE BUFFERING AFFECT OF CALCIUM CARBONATE


Curtis E. Swift, Ph.D.
Colorado State University
Cooperative Extension
Tri River Area Agent (Horticulture)

Western Colorado Soils
Reducing Soil pH
Buffering Effect of Calcium Carbonate

Western Colorado Soils
The acidity or basicity of a soil is referred to as pH and is based
on the concentration of the hydrogen ions in the soil solution. As
the hydrogen ion concentration (H+) in the soil increases, the pH
drops increasing the acidity of the soil. If the hydrogen ion
concentration drops in relationship to the hydroxyl ion (OH-)
concentration, the pH increases with the soil becoming more basic
(or alkaline). Since pH is based on a logarithmic scale of 10, each
unit change in pH (i.e. 7 to 6) is a 10 fold change in hydrogen ion
concentration.

Soils in the valleys of Western Colorado typically have a pH of 7.5
to 8.5 creating a basic/alkaline condition. Gardeners hoping to grow
blueberries (pH preference of 4.5) would need to change the pH
accordingly. When changing a soil from a pH of 7.5 to a pH of 4.5, a
1000 fold change in the hydrogen ion concentration would need to be
made.


Reducing soil pH
Soil pH is usually reduced by the use of acidifying agents such as
elemental sulfur or sulfuric acid. When sulfur is added to soil it
combines with water and oxygen through bacterial activity and
changes to sulfuric acid. This reaction takes place slowly over 6
to 8 weeks based on soil moisture and temperature conditions. It
should be noted that since this process is accomplished through
bacterial activity, when soil is pasteurized to eliminate pathogens
as is often done with houseplant potting soil, this acidifying
process is unlikely to occur as the necessary bacteria are killed.
Sulfuric acid is much quicker acting but should be used with caution
as previously mentioned.


The Buffering Effect of Calcium Carbonate
The soils of Western Colorado are highly buffered with free lime
(calcium carbonate - CaCO3). Any sulfuric acid coming into contact
with calcium carbonate will react producing water (H2O), carbon
dioxide (CO2) and calcium sulfate (CaSO4). No increase in hydrogen
ion concentration occurs in this reaction, consequently no change in
soil pH can occur. Instead, an increase in the salt level takes
place due to the resulting increase in concentration of the salt
gypsum (calcium sulfate - CaSO4).

If the free lime in Western Colorado soils could be neutralized, any
additional applications of sulfur or sulfuric acid would bring about
a pH change. Six tons of sulfur (or 20 tons of sulfuric acid) is
required per acre to neutralize each percentage of calcium
carbonate. Many western Colorado soils contain 5 percent or more of
calcium carbonate, thus 30 tons of sulfur or 100 tons of sulfuric
acid would need to be applied. With up to four thousand feet of
calcium-based Mancos shale under these valley soils and with the
irrigation water containing calcium carbonate, the possibility of
reducing pH in gardens and lawns is highly unlikely. Gardeners
wishing for an instant remedy for this problem can rest assured that
no such cure currently exists.

Greenhouse operators and homeowners working with potted plants can
effectively adjust pH as they are working with a finite amount of
soil. In those instances where a peatmoss based potting soil is
used, it may be necessary to raise the pH due to the acidifying
affect of the peat moss. Calcium carbonate (CaCO3) is typically used
to accomplish this task. When the pH of a potting soil needs to be
lowered as when growing citrus, azaleas or Easter lillies, the use
of sulfuric acid or sulfur may be needed.

Sulfur and gypsum (calicum sulfate) continue to be sold in Western
Colorado as remedies to correct the soil problems in gardens and
lawns due to a lack of understanding of the soil chemistry in the
area. Farmers and gardeners alike should avoid the use of gypsum
unless a soil test indicates a high sodium concentration and a low
lime content. Such a soil is know as a sodic or alkali soil. Western
Colorado soils are alkaline (pH above 7) and the two terms (alkali
and alkaline) are sometimes confused. Western Colorado has very few
true sodic soils and the use of gypsum should be avoided unless
indicated by a soil test.
_________________________________________________________________
Add MSN 8 Internet Software to your existing Internet access and enjoy patented spam protection and more. Sign up now! http://join.msn.com/?page=dept/byoa

---------------------------------------------------------------------
Pumpkin-growing archives: http://www.hort.net/lists/pumpkins/
To sign-off this list, send email to majordomo@hort.net with the
message text UNSUBSCRIBE PUMPKINS

Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index