On Apr 4, 1:44*pm, Billy wrote:
You are indeed correct, as to the original post, which is why I've
started a separate post, "Jeff Lowenfels called out".

Gardengal, with much hubris, claims that only the intrinsic soil
components determines the soil pH. For example, most of the U.S. east of
the Mississippi was once forest (acidic), in those areas where large
scale modern monocultures (injecting ammonia gas) don't exist, according
to Gardengal, that those areas should still be acidic because they were
once forest areas (historically acidic soil because of fungi).

Now, the above is just an example. The main nut of the thing is do soil
organisms change soil pH? I have no expertise in this area, so I must
rely on experts. Either Gardengal or Jeff Lowenfels is wrong, or they
will come up with a situation that I hadn't considered (which isn't too
far fetched). In any event, it should be a learning situation.

As you may remember, Jeff Lowenfels has posted here before and I'm
hoping he will respond, and perhaps we can all become a bit more
informed.

If anyone else would like to ask for his comment, his email is


In article ,





*"brooklyn1" wrote:
"Billy" wrote
gardengal wrote:

Plants do not make soil acidic - acid soils occur
as a result of the mineral content and amount of rainfall.

AAAAAAAAAAh - wrong

All nitrogen is not the same

Billy, you are correct. * But if one understands the original question
?growing grass under oak trees? the answer is far more simple than your
technical discourse.

*With a stand of pine trees (or oak trees), the needles/leaves that they
drop are going to have an influence on the soil pH *local* to the trees..
It's not the actual plant changing the pH, it is the vegetation decomposing
and adding to the soil that can indeed alter soil pH.

Other than light and water there is no other concept more basic to
gardening, anyone who doesn't comprehend this does not garden. *Anyone who
is any kind of gardener knows this instinctively. *That's why gardening
centers have stacks and stacks of lime (and peat moss) right near the lawn
growing products. *Anyone who doesn't know this simple fact of local plants
altering soil pH has never been to a garden center other than as a spectator
sport.

If someone is trying to grow lawn grass under any tree and the grass is
struggling the first thing even the most novice gardener does is test the pH
of the soil directly below the tree... anyone who has actually done any
gardening automatically tests soil pH *prior* to planting anything that
hasn't grown there previoauly... the same way one knows to put their socks
on before putting on their shoes a gardener checks soil pH under a tree
before planting grass, it's part of the soil preparation the same as with
planting a vegetable garden, a rose bush, even a corn field, etc., it's just
that simple.

I suspect some here do not garden... they only talk gardening... someone
else is doing their landscaping, and perhaps they help so they pick up the
nomenclature, that they toss around in an attempt to give credibility to
their preachings... this is true with any endeaver where someone is quick to
say others are wrong but cite no reference other than their own say so, and
then cannot reply with the correct answer, but instead hide behind a decoy
of nonsensical double talk/fluff speak.

Ultimately, from the plant's perspective anyhow, the role of the soil
food web is to cycle down nutrients until they become temporarily
immobilized in the bodies of bacteria and fungi and then mineralized.
The most important of these nutrients is nitrogen block of amino acids
and, therefore, life. The biomass of fungi and
bacteria (that is, the total amount of each in the soil) determines, for
the most part, the amount of nitrogen that is readily available for
plant use.

It wasn't until the 1980s that soil scientists could accurately measure
the amount of bacteria and fungi in soils. Dr. Elaine Ingham at Oregon
State University along with others started publishing research that
showed the ratio of these two organisms in various types of soil. In
general, the least disturbed soils (those that supported old growth
timber) had far more fungi than bacteria, while disturbed soils
(rototilled soil, for example) had far more bacteria than fungi. These
and later studies show that agricultural soils have a fungal to
bacterial biomass (F:B ratio) of 1:1 or less, while forest soils have
ten times or more fungi than bacteria.

Ingham and some of her graduate students at OSU also noticed a correla-
tion between plants and their preference for soils that were fungally
dominated versus those that were bacterially dominated or neutral. Since
the path from bacterial to fungal domination in soils follows the
general course of plant succession, it became easy to predict what type
of soil particular plants preferred by noting where they came from. In
general, perennials, trees, and shrubs prefer fungally dominated soils,
while annuals, grasses, and vegetables prefer soils dominated by
bacteria.

One implication of these findings, for the gardener, has to do with the
nitrogen in bacteria and fungi. Remember, this is what the soil food web
means to a plant: when these organisms are eaten, some of the nitrogen
is retained by the eater, but much of it is released as waste in the
form of plant-available ammonium (NH^). Depending on the soil
environment, this can either remain as ammonium or be converted into
nitrate (NO,) by special bacteria. When does this conversion occur? When
ammonium is released in soils that are dominated by bacteria. This is
because such soils generally have an alkaline pH (thanks to bacterial
bioslime), which encourages the nitrogen-fixing bacteria to thrive. The
acids produced by fungi, as they begin to dominate, lower the pH and
greatly reduce the amount of these bacteria. In fungally dominated soils,
much of the nitrogen remains in ammonium form. Ah, here is the rub:
chemical fertilizers provide plants with nitrogen, but most do so in the
form of nitrates (NO,,). An understanding of the soil food web makes it
clear, however, that plants that prefer fungally dominated soils
ultimately won't flourish on a diet of nitrates. Knowing this can make a
great deal of difference in the way you manage your gardens and yard. If
you can cause either fungi or bacteria to dominate, or provide an equal
mix (and you can just how is explained in Part 2) , then plants can
get the kind of nitrogen they prefer, without chemicals, and thrive.

p 25 -26

Teaming with Microbes: A Gardener's Guide to the Soil Food Web
by Jeff Lowenfels, Wayne Lewis

* ? *Publisher: Timber Press, Incorporated (July 15, 2006)
* ? *ISBN-10: 0881927775
* ? *ISBN-13: 978-0881927771
--

- Billy
"For the first time in the history of the world, every human being is
now subjected to contact with dangerous chemicals, from the moment of
conception until death." *- Rachel Carson

http://www.youtube.com/watch?v=WI29wVQN8Go

http://www.haaretz.com/hasen/spages/1072040.html

--

- Billy
"For the first time in the history of the world, every human being
is now subjected to contact with dangerous chemicals, from the
moment of conception until death." *- Rachel Carson

http://www.youtube.com/watch?v=WI29wVQN8Go

http://www.haaretz.com/hasen/spages/1072040.html- Hide quoted text -

- Show quoted text -

Alright......let me see if I can explain this so everyone
understands.

The chemical properties of a soil - its pH - is determined primarily
by its mineral content and secondly by the amount of rainfall it
receives. This is a well understood fact of soil science. Of course
there are other contributors but they tend to be minor players
unless......unless.....they have been added to excess. These would
include various pollutants, chemical fertilizers, mineral additives
and other amendments and yes, soil organisms. However, for soil
organisms to measurably alter a soil's natural pH, you would need to
add copious amounts of organic matter or organic fertilizers to
stimulate them into a feeding frenzy. The amount of organic or
inorganic acids they produce in the course of their natural
consumption of normal levels of organic matter is just not sufficient
to make major swings in pH levels. Most soils also have a natural
buffering capacity that resists any significant change in pH, which is
why it is very difficult, if not virtually impossible, to permanently
and significantly alter a soil's natural chemical compostion unless
frequent, repeated amendments are done to effect that change.

To address the topic of this discussion.........the reason many plants
are not inclined to grow under the canopy of any large tree has
nothing to do with soil pH. The conditions are just as inhospitable in
an acidic soil as they are in an alkaline soil. And that's because the
tree is higher on the plant pecking order, often casting dense shade,
creating dry conditions by preventing or diverting rainfall to reach
plants under its canopy and through its dense and very far reaching
network of fine feeder roots that suck up all available soil moisture
and ready nutrients. Plants that do tend to grow under trees are those
that can easily tolerate these conditions.......and lawns/turf grasses
are not one of them. Since large established oak trees have a dense
canopy as well as a very dense and spreading root system, it should
come as no suprise that lawns - even those that are shade 'tolerant' -
have a difficult time competing. For a gardener to reach first for the
soil pH testing kit when faced with this situation simply indicates a
lack of gardening sophistication and an understanding of basic plant
morphology.

If one does the research, they'll find there is really nothing to
substantiate the concept that normal debris accumulation from existing
plants alters soil pH. This is a gardening myth that has been
perpetuated by lack of understanding - pine needles or oak leaves,
etc. do not make a soil more acidic.There are many pines and oaks (and
junipers, etc.) that prefer and thrive in alkaline soils and the
shedding of their needles or leaves does not change that preference OR
the soil pH. They do leach some weak acids to the soil surface but
these dissipate as they percolate down and the pH of the soil any more
than an inch or so below the surface will be whatever that soil pH is
naturally. And as they decompose, even very acidic plant debris is
neutralized and approaches a neutral pH. That's why most compost tests
out at around 6.7 to 7.0 pH.

I think it would be more helpful to look this situation through a big
picture perspective. Dr. Ingram's research focuses on the microbiology
and how it interacts with the soil. And it does have an impact to be
sure. But it does not carry the load WRT the chemical compostion of
the soil. It is a bit part player that can be stimulated into a larger
role but never that of the leading man.

As to my credentials and the need to post cites, I'm not at all sure
how relevant that is to the discussion at hand. If one bothers to
research recognized, substantiated cites, the information is there for
all to see. I do happen to have a degree in horticulture, have various
professional certifications, teach part time for MG classes and at the
college level, have published on a minor level and have gardened
professionally (and personally) for several decades. But of course no
one has the ability to substantiate any of this, so take it or leave
it.