Re: CULT; Lime and Leafspot

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12/16/2005 3:09:41 PM Central Standard Time

Following is an excerpt for the garden column Spring '04 issue of Tall Talk
"That Bein' Said....." by Lazy Bill. You may find the the liming information
it
contains helpful.

As a point in passin', that Blyth feller you mention is not prone to lyin'.
He's much to far South to do such.
Smiles,
Bill Burleson

I'm told I can improve my tall bearded iris beds by adding lime. How much do
I add? Can I put too much? - Sara L.

Many sources advise adding lime to bearded iris beds. You are certainly
correct in doing so providing your current soil pH is below seven. The purpose
of
the lime addition is to reduce or neutralize the soil acidity. Most people
whose lively hoods depend on growing irises prefer growing them in a soil pH
range
between 7 and 8.

I hear a really southern, southerner (Australia) snows his ground with lime
and says he seemed to experience less leaf spot when he had done so. Another
southerner (south California) uses cement, the primary ingredient of which is
lime, to treat infected rhizomes for bacterial soft rot. These benefits I have
no reason to doubt but cannot now attest too. You will certainly be adding
calcium, a secondary plant nutrient that aids in the formation of root hairs
required by most plants in fairly substantial quantities, to your soil.

That being said, the primary benefit of liming is improvement in the bearded
irises' ability to assimilate nutrients from the soil. Determination of the
amount required is imprecise at best. It depends on the present pH of you
soil,
the composition of that soil, the depth to which you wish to alter the pH, and
the time frame you wish to maintain the soil in the recommended target range,
as well as the quality of the ground agricultural limestone you use. Ground
dolomitic limestone is also an option that contains only about half as much
calcium as ground agricultural limestone. It is best used when your soil
analysis
indicates your soil is deficient in magnesium. The two are roughly equivalent
in their acid neutralizing capacity.

If you want the most immediate results (recommended) use the finest grind of
agricultural limestone commonly available in your area. It is usually pretty
dusty. The speed with which the limestone will act is a function of how finely
ground the product is. Even using the finest grind (all particles pass through
a 100 mesh screen) it will still take about six months for it to fully react
with your soil. Once the limestone has fully reacted the pH of the soil will
begin a gradual reversion to its original pH. Soil pH is dynamic rather than
static, always changing.

Maybe because we so often deal with highly concentrated chemicals,
fertilizers, etc. or maybe because we just do not realize the quantities
required to
accomplish the desired results, we more often have problems not applying
enough
lime rather than too much. Sometime we stop adding the limestone believing it
did no good when in truth we just did not add enough. We might broadcast fifty
pounds over a ten by hundred foot bed, get it pretty white, and think, "Wow,
that's pretty good. Hope I didn't hurt my irises." It takes a lot of limestone
to make even small changes in a flower bed's pH and it's ability to do so
depends on the composition of the soil.

Sand and loamy sand require the least amount of lime to alter pH. Then
roughly linearly progressing amounts are required for sandy loam, loam, silt
loam,
and clay loam. Clay loam requires about five times as much lime as loamy sand
to affect the same pH change. A cooler region also requires significantly more
than a warmer one to affect the same change in otherwise identical soils.

Much like top dressing with fertilizer will help starved irises, top dressing
with ground limestone can help raise the pH of garden soils. But, like
fertilizer the greatest benefit is derived when it is deeply incorporated and
well
mixed into the bed.

Assuming you want to correct a 1000 square foot bed to fourteen inches of
depth from a pH level of 6.5 to 7.5 you will need to add about 128 pounds of
agricultural limestone if the bed is of silt loam composition. It takes a lot
of
limestone.

Warm Temperate Regions Appx. limestone requirement per 1000 sq. ft. to raise
pH level from 6.5 to 7.5 to a 14 in. depth
Sand and loamy sandb&b&b&b&b&b&b&b&b&b&b&b&........36 lbs.
Sandy loamb&b&b&b&b&b&b&b&b&b&b&b&.......................64 lbs.
Loamb&b&b&b&b&b&b&b&b&b&b&b&.............................b&92
lbs.
Silt loamb&b&b&b&b&b&b&b&b&b&b&b&......................b&128
lbs.
Clay loamb&b&b&b&b&b&b&b&b&b&b&b&....................b&184 lbs.

s Appx. limestone requirement per 1000 sq. ft. to raise pH level from 6.5 to
7.5 to a 14 in. depth
Sand and loamy sandb&b&b&b&b&b&b&b&b&b&b&b&........55 lbs.
Sandy loamb&b&b&b&b&b&b&b&b&b&b&b&.................... 119 lbs.

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