LETTERS TO
the editor
Opposing View
Dr. J. Benton Jones’
article “What Should We
Know About Biological
Inoculants?” (February
2011), is spot on, but only
if you are willing to pretend
that decomposition is the
only task accomplished
by biological activity in the
rhizosphere. Unfortunately it’s
not. Other far more vital functions of fungi and bacteria
are nutrient fixing, nitrogen cycling (nitrate/nitrite),
nutrient transport and “cracking” natural potassium
compounds to make them available. Even if all an organism
does is eat and reproduce and excrete, it is participating in vital
soil and rhizosphere activity. Not all of this is strictly related
to decomposition, though it is driven by the activity of the
organism. I would direct readers to a series of lectures given by
Dr. Elaine Ingham and Carole Ann Rollins, PhD entitled “
Adding
Biology for Soil and Hydroponic Systems, published by the
”
Sustainable Studies Institute, Corv allis, OR.
As to competition with the subject plant for soil resources,
in good organic practice, one feeds the organisms that by
their activity feed the plant, so “competition” for resources
isn’t what is happening at all. Only if you must persist in the
idea that you are feeding the plant by fertilizing in an organic
system does this assertion make sense. Ideally you are not;
you are feeding the natural nutrient cycling of the soil. If all
components of the soil are adequate, there should be no need
to add any fertilizer to the system at all. In the natural world
everything has its place. I disagree with Dr. Jones’ assertions.
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12
Maximum Yield USA | June 2011
GROWING
FOR HEALT
H
WHY SHO
ULD
Precise pH
ABOU
I CARE
T pH?
In the recent article,
“Why should I care about
by Charlen
e Rennick
pH?” there are some
Have you
misleading statements.
ever wond
“p” in “p
ered why
H”
the
while the is a lower-case let
“H
ter
Although hydrogen is an
does it me ” is capitalized?
What
an?
essential plant nutrient
element, pH has no
direct relationship
to the hydrogen
nutritional status of a
plant. The pH of the
rooting medium—
whether a nutrient
solution or a material
substance (organic or inorganic)—
does affect the ionic conditions that surround the plant
root and ion absorption, the optimum pH being on the acidic
side between pH 5.8 and 6.4. Actually the rhizosphere around
the plant root is very acidic, in the range between 4.5 and 5.5,
the acidity coming from the hydrogen ions generated by
root respiration.
Water is not primarily root absorbed by osmosis, but is drawn
into the root by the “pull” created by the transpiration stream.
As water is evaporated from leaf surfaces via transpiration,
the water column that exists in the xylem vessels in the entire
plant, provides the “force” that pulls water into the root. Some
ions that are in the water surrounding the root are also drawn
in, although most ions are selectivity absorbed.
There is no such thing as “hydrogen osmosis. The hydrogen
”
that is required by plants is derived from root absorbed water.
In the process of photosynthesis, a water molecule is split, the
hydrogen atom released combined with a molecule of carbon
dioxide to form a carbohydrate molecule, and in this process, a
molecule of oxygen is released into the atmosphere.
Osmosis is the movement of water through a semi-permeable
membrane into a region of higher solute concentration.
Osmosis only occurs in the so-called “free space” that exists
in root tissues. The ability of ions to move through the root
membrane against a concentration gradient from the solution
surrounding the root into the plant root requires energy that is
obtained from root respiration. This is why plant root function
requires that the surrounding root environment be aerobic.
Reverse osmosis devices generate pure water by passing
water through a series of membranes that strip ions and
molecules from the water. Reverse osmosis devices are
very efficient in removing all dissolved substances as well
as some small suspended molecular substances. Therefore,
the additional need to pass RO-generated water through an
activated carbon filter is usually not necessary.
“The leve
l of pH is
measured
of zero to
on a
14
highest con with zero represent scale
ing
centration
represent
of acid and the
ative of the
14
most alka
line.”
The “p” stand
s for potential
gen. Okay,
and the
so that mak
es it as clear “H” stands for hydroHydrogen?
as mud. Wha
A scientific
t is potential
explanation
to the plan
t’s ability to
would state
attract hydr
that pH refer
explanation
ogen ions.
s
says pH is
A less scien
the acid/alk
Translated
tific
aline balan
into a lang
ce.
uage those
understand,
of us
the
both the wate pH level refers to the without a PhD can
acidity and
r
alkalinity of
is too acidic, and the growing med
ium
that means
the plant will . If the environment
hydrogen,
whil
not attract
enough
tract too muc e an environment that
is
h
fluctuates from hydrogen. An environm too alkaline will atent that cont
one extre
unhealthy
inually
for the plan me on the pH scale to
t.
the other is
Hydrogen
is one of four
survive. With
elements all
out hydrogen
living plan
ts need to
able to take
, the plant
in nutr ients
would wilt
. Plants abso
and not be
water via a
rb hydrogen
process calle
d osmosis*
through the
cycle is wha
. This
t keeps nutr
ients traveling hydrogen-osmosis
the plant. Onc
from the wate
no amount e a plant has died due
of water that
to lack of wate r into
can
The level of
r,
pH is measure be added to it that will there is
zero represen
ting the high d on a scale of zero to revive it.
14
est concentr
ation of acid with
and 14
120
Maximum
Yield USA
| February
2011
JBJ
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