Subject: Calcium emphasis?

From: "Frederick R. Magdoff" <[email-masked]>
Date: Wed, 13 Jan 1999 20:53:20 -0500 (EST)

Victoria, Ann, Steve, and others,

    I am revising Building Soils for Better Crops and hope to have a
second edition puplished (through the SARE Program) within a year. IT is
keeping the emphasis on organic matter management but a numberof chapters
are being added to make it a more comprehensive work on ecological soil
management. I'm currently working on three nutrient management chapters.
I've already incorporated concepts on basic cation ratio material along
the lines of the very useful publication  by George Rehm  at the website
that Ann mentioned (BY THE WAY - a number of public labs including ours at
UVM and Penn State's uses a blend of the two systems - the sufficiency and
basic cation ratio) to recommend either K and/or Mg).
    What I am looking for is any research that relates to the tremendous
emphasis and priority that some people put on calcium. From what I've seen
there may be occasional situations where because of high Mg-minerals or
overuse of K fertilizer,  soil structure may be helped by added Ca. Also
in low organic matter soils that have highly dispersable clays and have
been well weathered, the extra salt provided with a Ca source like gypsum,
may help aggregate stability more than the Ca does. And I've done research
myself on reclamation of sodic soils with gypsum. But, in general, from
what I've seen, if the soils pH is where you need it AND the CEC is
reasonable, the chances are there is plenty of Ca for plant nutrition
(with possible exception of certain problems on selected crops such as
tomatoes (when conditions are there for blossom end rot)  and peanuts) and
stabilizing soil structure.  Any references on this issue would be greatly
appreciated.

FRED

******************************************************************************* 
				Fred Magdoff 
			Northeast Region SARE Program
				Hills Building
			    University of Vermont
			    Burlington, VT 05405
			       tel:802-656-0472
			       fax:802-656-4656
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