| SOIL,
FOOD, & PEOPLE CONFERENCE
March 27-29, 2000
GROW BIOINTENSIVE conference on the U.C. Davis campus
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PRESENTATIONS
Soil: Its Context in Sustainable Agriculture
Louise Jackson | Jeff
Mitchell
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Louise Jackson is an associate
professor and Cooperative Extension specialist in the Department
of Vegetable Crops at U.C. Davis. For over 10 years she has
conducted a research and teaching program in agricultural ecology
at Davis. |
Her goal is to use her research to improve water
and nitrogen management in vegetable crop systems, so that fertilizer
and irrigation inputs are reduced, and nitrogen losses to the environment
are minimized.
Jackson stated that as a biologist, she is interested
in the life of the soil, and how it changes with more organic matter
input and less pesticide and fertilizer. She is addressing how soil
ecology relates to sustainable agriculture. She said that interactions
in the soil are complex and hard to separate. It is necessary for
researchers to separate soil ecologies into their component parts.
In studying the partitioning and flow of nutrients
among soil, soil biota, atmosphere and ground water, the question
to ask is whether nutrients are retained or lost within the whole
system. In her research, it has been shown that cover crops are
instrumental in keeping nitrates from leaching to the subsoil during
winter rains and that lettuce is particularly efficient in absorbing
nitrogen from a cover crop.
Jackson said:
- they also study the ecology of the soil community, the composition
and interaction of all organisms in the soil, including plants
and how this affects nitrogen cycling,
- this is a very complex system and a difficult area to research,
- markers for soil organism identification are now starting to
be used and that these may eventually serve as fingerprints of
community soil organism composition
- a third area of study used is individual soil organisms and
how they change under various circumstances is a key area being
studied.
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Jeff Mitchell is a Cooperative
Extension vegetable crops specialist at U.C. Davis' Kearney
Agricultural Center. |
His work emphasizes soil quality assessment and improvement as
well as reduced tillage production systems.
Mitchell said that he has had the opportunity in the past 4 or
5 years to work directly with farmers in a team effort that includes
the USDA and other organizations. He stated that:
- the quality of the soil is the business of everyone at the conference,
- the ability of the soil to sustain its multitude of functions
has come under question, particularly in the last 2 decades, and
- defining soil quality has been a very difficult task.
Mitchell mentioned that on the west side of California's San Joaquin
Valley there was once a wide variety of crops grown, which returned
a great deal of organic matter to the soil. Today that area is mainly
monocropped, leading to serious concerns among its producers about
soil quality. He has been working with 15 farmers in the area to
provide answers about how the regular use of manure, compost and
cover crops affects the soil's organic matter, microbial activity
and fertility. After 3 years, the farmers were using these inputs
70% of the time.
Mitchell also explained how difficult it is to break down the mass
of data collected into component parts. They were testing the soil
for its physical, chemical and biological properties, which he said
had never been done before. At a different test site, near Davis,
they are also experimenting with reduced tillage methods, trying
to discover the optimal tillage to preserve the greatest amount
of carbon in the soil.
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