Anatomy of Healthy Soil

So what is healthy soil? Deceptively simple to the naked eye,
healthy soils are dynamic ecosystems made up of a mixture of
minerals, air, water, organic materials and a healthy population of
microorganisms. The range and concentration of minerals present
depends on the parent bedrock. Healthy soil is also extremely
porous: Air accounts for about half its volume, providing channels
for water to flow, pathways for roots and space for organisms to
move around. Compaction, primarily the result of heavy farm
machinery and livestock, squeezes air out of soil, depleting
available oxygen.

An acre of healthy topsoil can contain 900 pounds of earthworms,
2,400 pounds of fungi, 1,500 pounds of bacteria, 133 pounds of
protozoa, 890 pounds of arthropods and algae, and in some cases,
even small mammals. When this diverse soil community is disrupted or
damaged, the consequences may be dire.

the symbiosis between soil organisms and plants is deeply
intertwined. Many soil microbes feed on by-products from growing
roots and, in turn, help plants by extracting minerals and vitamins
from the soil. Like microscopic farmers plowing and tilling their
subterranean plots, these organisms enhance soil structure and help
control plant-preying pests, cultivating an underground ecosystem.

Soils also play an important role in the process of recycling
carbon, the most vital element for living beings. Healthy soils can
be an important carbon sink, binding up carbon that might otherwise
enter the atmosphere, potentially contributing to global warming.

According to the Environmental Literacy Council (ELC), soils contain
twice the amount of carbon found in the atmosphere, and three times
more carbon than is stored in all the Earth's vegetation.

Soils also play an important role in the process of recycling
carbon, the most vital element for living beings. Healthy soils can
be an important carbon sink, binding up carbon that might otherwise
enter the atmosphere, potentially contributing to global warming.

According to the Environmental Literacy Council (ELC), soils contain
twice the amount of carbon found in the atmosphere, and three times
more carbon than is stored in all the Earth's vegetation. humus—an
extremely rich component of soil the color of dark chocolate.
Hepperly explains that humus is saturated with carbon. "Organic
matter is really what holds water in the soil when you have droughts
or floods," Hepperly says. "If you take away the glue, everything
falls apart." Soils in Trouble

during the Dust Bowl years, "At least five inches of topsoil were
lost from nearly 10 million acres."

While erosion isn't as dramatic in the U.S. today as it was in the
1930s, the problem continues to haunt farmers and urban developers.
In a 2002 position paper adopted by ASABE, the group estimated that
soil erosion is damaging the productivity of 29 percent (112 million
acres) of U.S. cropland and is adversely affecting the ecological
health of 39 percent (145 million acres) of rangeland. Worldwide,
erosion is one of the biggest causes of soil degradation. "An
outrageous amount of soil is being lost," says Craig Minowa, an
environmental scientist with the Organic Consumers Association
(OCA).

Though a renewable resource in theory, soil forms very slowly,
measured in centuries. For all practical purposes, the soil we lose
to erosion will never be replaced in our lifetimes.

"The fastest soil regeneration is about 200 years, but it can take a
million years, depending on the geologic processes," says Dan Yoder,
a professor in the Department of Biological Systems Engineering and
Soil Science at the University of Tennessee. "Coarse sand, for
instance, doesn't form soil very easily."

In addition to being the most productive soil layer topsoil (it
contains the highest concentration of organic material), is also
the layer in which plants grow best. But topsoil is also the
thinnest layer, usually not more than a foot deep. Preston Sullivan
of the National Sustainable Agriculture Information Service says
that soil lost to erosion contains about three times more nutrients
and 1.5 to five times more organic matter than the soil that remains
behind. Further, loss of topsoil increases a soil's overall
vulnerability to erosion, thus creating a vicious, exponentially
worsening cycle of damage.

Population pressures are now forcing farmers to remain on the same
nutrient-depleted land to grow their crops year after year. After
farming a piece of land in many parts of the world, when production
decreased and people moved on. That only works with lower
population.

A 1995 study published in Science concluded that the loss of soil
and water from U.S. cropland decreases agricultural productivity by
about $27 billion per year. A 2000 story in the Australian rural
weekly paper Landline estimates that soil degradation costs
Australian farmers $2.5 billion a year in lost production. It added
that nobody has even calculated the off-farm costs of soil
degradation, such as salt-polluted rivers or the loss of
biodiversity and wildlife habitat.

The Environmental Protection Agency (EPA) reveals that at least 40
percent of the affected stream miles and 45 percent of lake and
reservoir areas were damaged because of eroded sediments. More
broadly, Blatt writes that farms produce 70 percent of all stream
pollution in the U.S.

One of the major problems with urban erosion, Yoder explains, is
that there is currently no unified national standard for erosion
monitoring and control at construction sites. While soil
conservation measures on farms were adopted in the 1970s and `80s
requiring farmers who receive federal support to prove they had
adopted conservation practices, no such regulatory structure exists
at urban construction sites. "You have the EPA watching, but each
state has its own agency for permitting of construction sites,"
Yoder says. "There's not much concentration on soil conservation."

One reason why agriculture can be so detrimental to soils is because
of the sheer scale of most farming operations today. According to
USDA, since 1900 the number of farms has fallen by 63 percent, while
the average farm size has risen by 67 percent. In 1900, the average
farm size was less than 100 acres; in 2002 it was more than 400
acres. Farm operations have also become increasingly specialized,
from an average of about five commodities per farm in 1900 to an
average of one per farm in 2000.

According to David Tilman, who wrote the 1998 Nature article "The
Greening of the Green Revolution," only about half of all
fertilizers are absorbed by plants. The remaining chemicals pollute
the atmosphere, soils and waterways.

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