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 more successful.
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
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 well.
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
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 nematodes1.
Researchers 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."