Posted September 14, 2006: "The nature of
soil on the outermost layer of the earth is to regenerate,"
said George Bird, PhD, associate chairperson of Michigan State University's
Department of Entomology, at a recent Rodale Institute field day.
"When left alone, this is where matter and energy are transformed
and transported, creating a regenerative system."
More than 30 years ago, Robert Rodale coined the term "regenerative
agriculture" to describe a farming system that improves upon
itself—regrows or restores the health and vitality of the
land. At the Institute’s field day in July, regeneration was
still a point of discussion. Ardath Rodale, co-chairperson of the
board of directors, opened the day with the history of the Institute's
333-acres—how the land has grown from barren and abused dust
bowl to richly productive farmland by following the logic of "Healthy
Soil = Healthy Food = Healthy People."
Following the opening remarks, the 110 attendees boarded wagons
that took them past experimental plots and long compost windrows
to five workshops. Each session featured techniques that would not
only stem the loss of soil on their farms, but would actually improve
the soil’s health by allowing regenerative processes to be
From no-till management to compost production, organic cropping
systems to ecologically-based weed management, the schedule was
full of information on what to do. But if the question
you ask is why do these techniques improve soil, Dr. George
Bird's workshop "The Living Soil on Your Farm" was the
place to be. He provided a small glimpse into the ecosystem we call
"dirt" and explained why certain cropping and management
practices can make such a huge difference in the profitability of
your farm for years to come.
The world in a speck of dirt
"Soil is an ecosystem—roots, earthworms, bacteria, etc.—all
working together as a unit," began Dr. Bird, "But we have
to realize, when we talk about ecosystems, that ecology-science
is only about 50 years old."
Compared to other biological sciences, the study of the relationships
between living organisms and their environment is in its infancy.
We're just beginning to look at, much less understand, why and how
the various organisms in the soil interact with each other and what
affect they have on the crops that live and grow in that soil as
As an example, when Bird asked, "How many kingdoms of organisms
do we share this planet with?" most attendees answered "two."
He went on to explain that in the time between when these folks
were learning ecology and today, we've established there are at
least five and may even be as many as 23 kingdoms of life with which
we share the earth. Everything but plants, animals and fungi are
microscopic and offer a tremendous diversity of organisms.
Feed your nematodes, feed your plants
Bird explained that eight of the possible 23 kingdoms of organisms
consist of decomposers. "These organisms decompose this hay/straw
and it goes into the body of bacteria," he said as he ripped
a handful of straw from a nearby bale.
While many living organisms are usually made up of a carbon-to-nitrogen
ratio of 50:1, some bacteria have a ratio of 5:1 which means they
require a huge percentage of nitrogen (N) to survive. "They
need a lot of nitrogen, but, if they live in a difficult environment,
they will conserve nitrogen," said Bird. "The
nitrogen from that decomposed hay/straw is then trapped inside the
bacteria, which means it is not available to the plants. Another
organism is required to release that nitrogen."
Bird insists the nematode, another microscopic organism in the
soil, is one of the farmer's best friends when it comes to maintaining
or improving the soil, helping you work with rather than against
Mother Nature. "I'm a lot of things....entomologist, pathologist,
soil biologist," said Bird, "...but mostly I know about
nematodes." The vast majority of nematodes make that "trapped"
N available, Bird said, and they can be used as an indication of
the quality of your soil.
Bird highlighted what he considers one of the most important research
papers in the past 50 years, which focused on improving yields with
started with soil that contained very little biomass, or living
material. They added a particular bacterium and were able to bump
the yield of the plants in that soil to five times what it was before.
They then added a bacterial feeding nematode to increase the release
of N and make it available to the plants.
"I don't usually say things like this, but you could probably
win the county vegetable competition with what came out of that
soil," exclaimed Bird.
As another example, Bird discussed a research project comparing
soil from eight cherry orchards in Michigan2.
Four were organic and four conventional. The researchers completed
an assessment of the soil by counting organisms that help cycle
the minerals the plants need for good growth. The organic soil had
a rich community of a quarter million bacterial-feeding organisms—some
nematodal, some fungal—all working together in balance.
The conventional soil had just 25,000 bacterial-feeding organisms,
and the population density of the plant-feeding nematodes was significantly
higher in the conventional orchards than the organic orchards, meaning
there were more organisms feeding on the root systems of the plants.
When the researchers then compared the impact on fruit production,
they determined that over a period of time, the organisms in the
organically-managed orchards doubled the active nitrogen and increased
the carbon by 50 percent in the soils, an indication of a potential
increase in yield and competitive fruit production.
How exactly do these little critters called nematodes manage to
make so much nitrogen available that yield is affected so dramatically?
It's a simple matter of bathroom science.
"Why do we all have a urinary system?" Bird asked. "We
have to excrete excess nutrients because holding more than we can
use can be toxic. Nematodes need to do this, too." The most
common nematodes are bacterial-feeding with a carbon-nitrogen ratio
of 10:1, he explained. When they consume bacteria they've doubled
their nitrogen. Since they only need a particular amount to function,
they have 50 percent excess nitrogen that needs to be released.
"They release that excess nitrogen in an ionic form either
directly onto the plant-root surface or in the immediately surrounding
environment before it has a chance to go down into the ground water
or up into the atmosphere," said Bird. The nematodes "fix"
nitrogen right were it can be best utilized by your plants—no
runoff, no waste.
Structure + process = results
"Your soil (structure) and what you do to it (process) give
you your results," explained Bird. Looking at the nematode
community should be part of regular structural assessment of your
soil as it can tell you quite a bit about the health of your soil.
Dr. Bird asserts that only once you've assessed the current structure
of your soil can you determine what processes are best applied to
that field to give you the results you want.
One of your first orders of business as a good manager, Bird said,
is to look at your soil biology and nematodal community. If it is
lacking, the question you should ask is: What process can I use
on this field to improve its long-term health and viability? If
it is already strong, the question you should ask is: What process
can I use on this field to accomplish my task without destroying
the existing health of the soil?
"Agriculture itself is disturbed ecology," said Bird.
"Your aim is to achieve your desired crop yield and quality
results with minimal soil disturbance."