In article om,
" wrote:

Some comments in line


...snip... quite good stuff on the role of microbes and plants

Soil life creates soil structure


A good point.

...

of snakes, birds, moles, and other animals. Simply put, the soil is one
big fast-food restaurant. In the course of all_ this eating, members of
a soil food web move about in search of prey or protection, and while
they do, they have an impact on the soil.


Nicely put.

.....

The soil food web, then, in addition to providing nutrients to roots in
the rhizosphere, also helps create soil_ structu the activities of
its members bind soil particles together even as they_ provide for the
passage of air and water through the soil.

Soil life produces soil nutrients

When any member of a soil food web dies, it becomes fodder for other
members of the community. The nutrients in these bodies are passed on to
other_ members of the community. A larger predator may eat them alive,
or they may _be decayed after they die. One way or the other, fungi and
bacteria get involved,_ be it decaying the organism directly or working
on the dung of the successful_ eater. It makes no difference. Nutrients
are preserved and eventually are retained in the bodies of even the
smallest fungi and bacteria. When these are in_the rhizosphere, they
release nutrients in plant-available form when they, in_ turn, are
consumed or die.

Without this system, most important nutrients would drain from soil.
Instead, they are retained in the bodies of soil life.

Not necessarily. Many nutrients are bound fairly tightly to colloidal
surfaces in clay and humous. OK the microbes have a big role in
making humous but they don't make clay.

Here is the
gardener's truth: when you apply a chemical fertilizer, a tiny bit hits
the rhizosphere, where it is absorbed, but most of it continues to drain
through soil until it hits the water table._

Once again not necesarily. If you have sand-based soil you spend you
life building it up with organic material to stop this happening but
with clay-based soil you don't, they hold most nutrients well.


..snip....


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.

What does 'mineralized' mean here? It's not clear to me.

...snip..


Ingham and some of her graduate students at OSU also noticed a
correlation 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 (NH3).

I presume they mean NH4+ the soluble ammonium cation (positively
charged particle), NH3 is ammonia gas.

Depending on the soil
environment, this can either remain as_ ammonium or be converted into
nitrate (NO3,) by special bacteria.

Here they mean NO3- the soluble nitrate anion (negtively charged
particle).

Why am I being picky about these being ions (that is charged)?
Because the fact that they are charged is important to understanding
how they bind to colloids, which is key to nutrient retention, a point
which is overlooked by the author.


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 (NO3). 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.


All well and good but ignores the fact that the alternative to adding
synthetic nitogen compounds (ignoring nitrogen fixing for now) is
adding manures or urine. It's true that these don't contain much in
the way nitrates from the beast but nitrates are formed naturally in
manure heaps. Gunpowder use to be made from potassium nitrate
gathered from manure heaps.

Negative impacts on the soil food web

Chemical fertilizers negatively impact the soil food web by killing off
entire_ portions of it.

Evidence please. The following isn't good enough.

What gardener hasn't seen what table salt does
to a slug?

Irrelevant. You don't put salt (sodium chloride) in your soil and the
way it kills slugs has little to do with the topic. Remember that
salts are a class of chemical substances which are NOT just common
salt (sodium chloride) in general, although sodium chloride is in fact
a salt.

Fertilizers are salts; they suck the water out of the
bacteria, fungi, protozoa, and_ nematodes in the soil.

In excess yes. In excess synthetic fertiliser AND natural ones will
both kill your plants in the same way. This does not mean that there
are no dissolved salts (as ions) in healthy soil nor does it mean that
you should never add such ions to your soil. You do it every time you
apply chicken manure or **** on the lemon tree.

...snip...


If the salt-based chemical fertilizers don't kill portions of the soil
food web, rototilling will.

Agreed. Once your beds are established heavy soil turning either
manually or mechanically is harmful rather than helpful.


.snip....


Overall this is not a bad chapter but (unless some details are
corrected in later chapters) it is incomplete and in part misleading.
The main point that soil is a living community that must be maintained
is very valuable.

David

Your a damn fine skeptic mate. Let me see if I can make another run at
this. I'll get back to you soon. Sorry, it's a bit late for me and I'm
ever so slightly hammered.
--
Billy
Coloribus gustibus non disputatum (mostly)