Fall, 1992 (v5n1)
Rodale Institute
Proceedings of a conference hosted by the Rodale Institute, July
11-13, 1991. Emmaus, PA. 1991
"Our responsibility is to return to the soil the vitality it so generously shares with us and to ensure that vitality for generations to come."
-John Haberern, president of Rodale Institute
This conference report documents the first steps of a national
effort to define and describe methods of enhancing soil quality.
The premise of the conference is that soil is a vital resource
for human survival, and as such, we must manage it to ensure long-term
agricultural productivity. As summarized in the conference conclusions,
any definition or discussion of soil quality issues should address
the three major functions that soil serves on our planet:
- soil is an essential link in the cycle of life
- soil is a medium for the growth of plants and animals
- soil acts as an environmental buffer.
The Scientific viewpoint
From a scientific viewpoint, the purposes of the meeting were
(1) to determine how soil quality can be characterized, (2) to
establish the key indicators of soil quality, and (3) to discuss
how these indicators can be monitored in the field and reported
in the form of an index. To accomplish this, a working group
session was organized to develop an operational framework for
addressing soil quality issues. This session led to the formulation
of a multi-level structure for defining which soil properties
to use in monitoring soil quality. The hierarchy that was developed
can be summarized as follows:
A. First define the target area or agroecosystem in which you
are working.
B. Next, assess how soil quality affects three key components
of the agricultural system:
- plant and animal productivity,
- the environment, and
- human health.
C. Determine which "meso-level" components of soil quality
(e.g. tilth, fertility, nutrition, presence of toxics) have the
strongest influence on each of the above components.
D. For each component (productivity, environment, human health),
examine the related "first order" soil properties.
- Chemical: electrical conductivity, pH, site-specific toxicities.
- Physical: soil texture, water holding capacity, bulk density, infiltration rate, soil depth.
- Biological: soil organic matter, microbial biomass, earthworm abundance, vegetation.
E. Continue with a closer assessment of "second order"
properties such as aggregate stability, amount of dispersable
clay, and the numbers and diversity of key soil fauna and flora.
Conference participants were challenged to take the next step
of integrating the many components into a useful index. It was
proposed that the index be expressed in equation form as a function
of the various factors outlined above. The index would therefore
be based on standard soil property analyses and soil survey methods
to establish a base line measure for soil quality. It would also
be dependent on continuous monitoring and comparisons with long-term
research sites in order to identify the direction of soil quality
change (particularly the risk of soil degradation), and estimate
the rate of soil quality change. Some soil quality factors would
be weighted more or less depending on the particular location
and conditions.
Broader Perspective Needed
The working group concluded that the effects of soil quality on
human health are the least studied and possibly the most complex
of the three major soil quality issues. In spite of the fact
that sustaining a healthy population is a fundamental goal of
agriculture, we tend to focus primarily on production and usually
ignore the nutritive content of food and its effects on human
health. There are examples from the literature that clearly show
that food nutritive content varies with soil characteristics (see
Components 3(1):9-10). Soil factors, climate and management
practices can all play an important role in determining the ultimate
nutritional quality of plants. Therefore, one recommendation from
the conference was that a greater effort should be made on routine
testing of food quality for crops grown under various management
practices. In addition to standard nutrient and mineral analyses,
researchers need to develop bioassays that can replace expensive
animal feeding trials.
Conference Recommendations
Several other recommendations from the conference include:
- A working task force should be established to further develop the components of a soil quality index, to assess the state-of-the-art in understanding soil quality, set research priorities, and to develop a strategy for implementing an international program for assessing and monitoring soil quality.
- Establish a working group specifically charged with summarizing the indicators of, and approaches to, soil quality. This group would develop a handbook of approaches and standardized methods for measuring soil quality.
- Establish, with adequate support, a research group dedicated to evaluating various models and approaches that assess and monitor soil quality. This group would interact closely with the working group assigned to developing the "Methods" handbook, and should also address the human health issue discussed above.
- The scientific community needs to promote further research on relationships between soil and crop management, soil quality, food quality and human and animal health.
- International research centers should be encouraged to identify research on soil quality as part of their mission.
The need for assessing soil quality -local and regional perspectives (Granatstein and Bezdicek)
Characterization of soil quality: Physical and chemical criteria
(Arshad and Coen)
Soil biological criteria as indicators of soil quality: Microorganisms
(Parkinson)
Soil and crop management strategies for improved soil quality
(Karlen, Nash, and Unger), and
Factors affecting the nutritional quality of crops (Hornick).
Papers from the conference will be published in the American
Journal of Alternative Agriculture this fall.
For more information write to: Carole Piszczek, Rodale Institute,
33 E. Minor St., Emmaus, PA 18098.
(DEC.376)
Contributed by David Chaney
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