Subject: Soil Quality Attributes

From: Marc Safley <[email-masked]>
Date: Thu, 23 Feb 1995 07:58:03 -0500

Not to try to beat this issue to death...that is not the point of this message;
the distinction between soil quality and soil attributes that make them
usable is one that needs to be ironed out in a better way if we are to
clearly conceive and test soil quality indicators.

The fact that soils of all types can respond to management inputs
is one upon which the industrial model of agriculture has depended.  In
many cases soils that would otherwise be unsuited for crop production
have produced bumper yields.  The question is not whether or not this
should be a consideration for agriculture so much as it is whether or
not this should be a criteria for determining soil quality.

The discussions of soil quality have focused on improving or
regenerating lost capacity of soils that have been damaged by intensive
agricultural management.  I suggest that this is the proper avenue of
thought.  If it is necessary to describe the ability of soil to respond
to physical and chemical management so that production is made
either possible or profitable then perhaps there should be a separate
parameter by which we assess soil response...we could call it
response to management for lack of a more creative term.

Thank you for the quality discussion.

Marc Safley
Natural Resources Conservation Service
[email-masked]

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From: "E. Ann Clark, Associate Professor" <[email-masked]>
Date: Thu, 23 Feb 1995 08:50:37 EDT

I have been observing the discussion on soil quality and would like
to add a query.  An issue which has been taken up with fervor by my
colleagues in soil science has been the notion that potential for
nitrate contamination of groundwater is **reduced** by using chemical
rather than organic sources of N.

The logic presented is that organic matter mineralizes in
ways/rates/timing which a) is not controllable, and b) is not easily
predictable, and hence, c) has the potential to continue to pump out
labile N long after the crop has been harvested.  On this basis, they
discount the merit of long-held organic farming wisdom, namely, "feed
the soil" as a source of immobilized and slowly released mineralized
nutrients to feed the crop.  The next dimension to this logic is that
perennial forages, which enhance soil OM, are hazardous to the
environment because when they are plowed under, they mineralize and
release copious amounts of N - with again, the potential to pollute.

In response, I can only agree with their logic **if** one continues
to crop in conventional ways - with the land bare or under dead
stubble for 7- 10 months of the year.  However, a great deal of the
rationale behind organic field crop agriculture is to keep the land
covered with a live - and predominantly, growing - crop year-around.
This practice, in addition to supplying a sink for labile nutrients,
also keeps the soil colder longer and enhances the synchrony between
such T-sensitive processes as microbially-based mineralization and
plant-based uptake.

I would be interested in the comments of SANETers on these issues,
particularly as they pertain to the definition of soil quality, and
ultimately, the attributes of the "ideal" soil that we should be
shooting for.  Ann

[email-masked]
Dr. E. Ann Clark
Associate Professor
Crop Science
University of Guelph
Guelph, ON  N1G 2W1
Phone:  519-824-4120 Ext. 2508
FAX:  519 763-8933