As a consultant and a grower I have utilised Albrecht's work along with
what I was taught in conventional soil science. That information married
with the techniques and practices from organic agriculture appear to be
able to provide a good foundation for sustainable agricultural
practices. One of the many things I look at in a soil analysis is the
total cation exchange, it gives me an indication of what nutrients are
able to be held in the soil available for plant growth. Knowing the clay
mineralogy is also helpful as far as indicating how degraded the soil is
likely to be in the context of the weathering cycle. Other than adding
high cation exchange clays to the soil (not very practical for the
average farmer) the addition of organic matter to provide humus is the
only other way of increasing the exchange capacity of a soil.
Balancing nutrient elements as suggested by Albrecht has been a
succesful management tool and until I can find a soil scientist that has
done similar research and demonstrates a different set of ratios that
should be used I guess I will continue along these lines. I am sure he
is not the only soil scientists that has provided inspiration to
agriculturalists, but his papers/books are not a bad start for those who
are interested in expanding their knowledge in this field.
I look forward to further comment on this fascinating topic.
Chris Alenson
Technical Adviser
Organic Advisory Service
Organic Retailers & Growers Association of Australia
----------
From: Sean Clark[SMTP:msclark@ucdavis.edu]
Sent: Thursday, 12 February 1998 9:54:am
To: sanet-mg@shasta.ces.ncsu.edu
Subject: Cation balancing in organic farming
Soil Saneters:
I am seeking some common ground and understanding on an issue
which seems to
be of extreme importance to many organic farmers and consultants
but given
little attention by academic scientists - that is soil cation
balancing and
the importance of calcium (Ca) in soil structure.
Time and again, when speaking with organic farmers and the
consultants who
serve them, I find the importance of cation balancing and soil
Ca come to
the center of the conversation. In lay terms, the basic idea is
that
inadequate exchangeable Ca results in poor soil structure,
characterized by
"tightness" because the amount of pore space for air is less
than optimal.
Consequently, root health is compromised and nutrient
availability and
uptake reduced. A general rule often given is that the ratio of
Ca to
magnesium (Mg) should be about 5-7 to 1. If it is less - you
need to add Ca.
As the research manager of a long-term study/comparison of
organic,
low-input, and conventional farming systems at the Univ. of
California at
Davis, I am sometimes criticized by these folks for giving
inadequate
attention to this issue. In this study, all of the farming
systems are
managed according to "best farmer management" strategies - which
are
determined by a group of academic and Extension researchers,
Extension farm
advisors, and farmers. Admittedly, we have not made or altered
any
management practices in this study based on soil Ca:Mg ratios.
Consequently, some organic farmers and consultants argue that
the organic
system in this study is being shortchanged because we have not
given the
soil Ca:Mg ratio proper attention.
When I ask where I can get more information on this matter I am
usually
referred to William Albrecht and his Papers. He published a
number of
studies during the 1920-1940s in the J. Amer. Soc. Agron. but I
have found
that his name now seems to be reserved for the pages of Acres
USA (not to
diminish Acres USA). My point is that I find no recognition or
ackowledgement of him or his work in basic or advanced textbooks
on soil
science and fertility management or among research scientists -
even among
those who are doing research on organic and low-input
agriculture. It seems
that Albrecht is to many in the organic movement what Stinner is
to the
Biodynamic movement. I see some people adhere to his "Papers"
with almost
religious conviction.
Getting back to my problem: The Ca:Mg ratios of the soils at
this study site
are nowhere near 5-7:1. In fact, they are less than 1:1. The
Ca:Mg ratio
in the organic system in this study is significantly
(statistically) higher
than that of the conventional system due to the Ca in the
composted and aged
manures that have been added over the years, but in absolute
terms the
difference is still quite small. There is a clear difference,
however, in
water infiltration rates between the organic and conventional
systems.
Rates are much greater in the organic system (which we presume
is due
largely to the higher soil organic matter levels in this
system).
Therefore, if any of the farming systems in this study is in
need of
management to remedy a soil structural problem it would be the
conventional
system. And, indeed, the group has discussed applying gypsum to
improve
infiltration rates in the conventional system.
However, the claims go beyond simply improving soil structure to
enhance
root growth and plant health. I am also told that the nitrogen
(N)-use
efficiency of the organic system would improve and that disease
severity
would decline with an increase the Ca:Mg ratio. The latter
doesn't
particularly interest me right now because diseases have not
been a serious
yield-limiting factor in any of the farming systems. But, the
potential to
improve N management in the organic system does. As many
studies comparing
organic to conventional systems have found, the release of
mineral N from
organic amendments and soil organic matter and uptake by the
crop are not
always predictable. Hence, we generally apply considerably more
N to
'nitrophilic' crops in the organic system to compensate for
unpredictable N
mineralization and make up for that taken up by soil microbes or
weeds. But
losses from the organic system (due to leaching,
denitrification, and
volatilization) are not any greater in the organic compared to
the
conventional system. Therefore I do not see how the addition of
Ca would
reduce the amount of N which needs to be added - even over a
long term.
Ouestions:
Are Albrecht's views accepted by "mainstream" soil scientists or
are his
ideas considered fringe? Do any university laboratories adhere
to any of
his concepts? Can anyone direct me to studies on Ca:Mg ratios
and cation
balancing (I have found very few)? Also, do any growers on the
list have
personal experiences with using soil Ca:Mg ratios in fertility
or disease
management ?
Thanks in advance,
Sean
M. Sean Clark
Research Manager
Sustainable Agriculture Farming Systems Project
Department of Agronomy and Range Science
University of California
Davis, CA 95616
msclark@ucdavis.edu
TEL:(916) 752-2023
FAX:(916) 752-4361
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