TOOLBOX / BSLA
understanding about the continuous
“conversation” occurring between plants
and soil. Until recently, methods for
assessing microorganisms didn’t exist.
Testing was limited to laboratory analysis
for physical gradation, chemistry, and
organic content, using technology initially
developed in the early 20th century and
often taking a week or more to receive
results. Now, soil biology tests are available
but only a handful of labs do this and the
turnaround times are just short of a couple
of weeks. We can do better by tapping into
emerging technology. Could there be on
the spot testing through an application on
a smart phone? What kinds of tests would
be most helpful and practical? And could
those results arrive within minutes instead
of waiting for a lab report?
Before new technology can be designed to
test the soil there needs to be understanding
about the elaborate forms of communication
happening between the biological life in soil
and plants, which have evolved for millions
of years in all trophic levels of life. This
begins with understanding the basics of the
science of soil.
Plants and soil are fused as one living,
breathing, organism that requires
one another’s biological processes to
continue fostering life. For plants, carbon
sequestered in leaves during photosynthesis
becomes foods such as sugars, proteins,
and carbohydrates. Up to 80% of these
foods either directly feed fungi, such as
mycorrhizae, or are exudated by the root
system to feed plant-specific bacteria and
fungi. In ecology, this is known as the
carbon flow and because soil is a carbon
sink it has a big role to play in this process.
Above
Black and white
electron microscope
images of soil
microorganisms
The growth of soil organisms are critical
for plant health because they decompose
exudates from plants and organic matter
while immobilizing needed nutrients that
plants require to grow. Larger predators
in the soil harvest these microscopic
organisms, and in the process, release
bound-up nutrients back into the soil in
plant-available form to feed the plant, which
increases the cycle of carbon sequestering
and food-making capacity for both soil
organisms and plants. One can’t operate
without the other.
Many of these organisms also release “glues”
that bind sand, silt and clay into a healthy
soil structure, which allows water and air
to freely move through the soil, regulate pH
(this adjusts bacteria to fungi ratio), and hold
valuable clay particles in the rhizosphere (a
microscopic layer of soil surrounding roots)
to maintain high cation exchange capacity
(CEC is a measurement of a soil’s ability to
Boston Society of Landscape Architects Fieldbook
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