On Apr 4, 10:22Â*am, Billy wrote:
In article
,

Â*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

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‹the basic building
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

Â* Â*€ Â*Publisher: Timber Press, Incorporated (July 15, 2006)
Â* Â*€ Â*ISBN-10: 0881927775
Â* Â*€ Â*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." Â*- Rachel Carson

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

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

God, you're a bit of an irritant, aren't you?

If you had done any serious study of soils aside from only reading
what has been written by others, you would know that what I wrote is
entirely correct. Plant life and soil microbial content has only a
minimal impact on unamended soil pH. Soil pH is dependent primarily on
the two factors I stated - the native mineral content of the soil and
the amount of rainfall it receives. Areas of high rainfall tend to
have acidic soils; arid locations tend towards alkalinity. Plants
that grow in acidic soils did not create that situation nor do they
make them more so - that's mistaking representation for causation.
Plants grow in acidic or alkline soils because that is to their
liking. Oak trees don't create acidic soil - they grow in acidic soil
because that is their preference. Acidic plant debris on the surface
of the soil can create a slightly lower pH on that surface, but it
does not penetrate to any significant depth into the soil strata. The
amount of organic matter one adds through incorporation - not just
lying on the soil surface - to a soil can lower pH but it would take
considerable quantities to affect any significant change. That's why
it is recommended to add minerals - sulfur or lime - NOT organic
matter or other plant life to alter a soil's natural pH.

"The parent material of soils initially influences soil pH. For
example, granitic soils are acidic and limestone-based soils are
alkaline. However, soil pH can change over time. Soils become acidic
through natural processes as well as human activities. Rainfall and
irrigation control the pH of most soils. In humid climates, such as
the northeastern United States, heavy rainfall percolates through the
soil. When it does, it leaches basic ions such as calcium and
magnesium and replaces them with acidic ions such as hydrogen and
aluminum. In arid regions of the country (less than 20 inches of rain
per year), soils tend to become alkaline. Rainfall is not heavy enough
to leach basic ions from soils in these areas.

Other natural processes that increase soil acidity include root growth
and decay of organic matter by soil microorganisms. Whereas the decay
of organic matter gradually will increase acidity, adding sources of
organic matter with high pH values (such as some manures and composts)
can raise soil pH.

Human activities that increase soil acidity include fertilization with
ammonium-containing fertilizers and production of industrial by-
products such as sulfur dioxide and nitric acid, which ultimately
enter the soil via rainfall. Irrigating with water high in
bicarbonates gradually increases soil pH and can lead to alkaline
conditions.

In most cases, changes in soil pH, whether natural processes or human
activities cause them, occur slowly. This is due to the tremendous
buffering capacity (resistance to change in pH) of most mineral
soils."