February 2022 - 26

PLANT & SOIL HEALTH
Work seeks to rebuild soil microbiomes in high tunnels
By Amy Duke
Penn State University
The presence of high salt and nitrogen
concentrations in high-tunnel soils may
make it more challenging to rebuild a
healthy soil microbiome following a soilclearing
event, according to microbial
ecologists in Penn State's College of
Agricultural Sciences.
Their research findings have
important implications for soil fertility,
and by Extension, crop health and
yield, said Laura Kaminsky, a doctoral
candidate in plant pathology, who led
the investigation under the guidance
of Terrence Bell, assistant professor of
phytobiomes.
" Plants generally grow better with
an active and diverse community of
bacteria, fungi and other microbes in
the soil, " she said. " If these microbes
are wiped out by a soil-clearing event,
we want to know how quickly the soil
microbiome bounces back and which
microbes are most successful at
re-establishing. Our study is laying the
groundwork for the future development
of guidelines that will aid farmers
when rebuilding soil through microbial
additives. "
Laura Kaminsky, a doctoral candidate in plant pathology, plans to pursue Extension or
nonprofit work that advances sustainable agriculture. Photo: Laura Kaminsky
The researchers focused on
agricultural systems that use high
tunnels, which are plastic, greenhouselike
structures placed over a section of
field soil. These structures are used to
extend the growing season and to grow
high-value crops such as tomatoes in a
more protected setting.
However, the quality of the soil under
high tunnels tends to degrade over
time. " If the same crop is grown in a
high tunnel year after year, pathogens
specific to that crop accumulate at
higher and higher levels in the soil
and cause increasing amounts of crop
disease, " Kaminsky said.
One way to manage this increasing
disease pressure is to reduce the
population of pathogens by wiping out
the entire soil microbial community,
which is done with chemical
fumigation or less harsh practices such
as anaerobic soil disinfestation and soil
solarization.
The problem, Kaminsky pointed
out, is that these soil-clearing practices
indiscriminately eliminate soil
microbes, including microbes that
provide benefits to crop plants and
microbes that perform general soil
functions like nutrient cycling.
Kaminsky and Bell's experiments,
which took place in Buckhout
Laboratory in 2018 and 2019,
specifically looked at whether high
soil salinity and high soil nitrogen
concentrations - two soil properties
that often develop under high tunnels
over time - altered soil microbiome
development.
To do that, the researchers buried
small nylon mesh bags containing
unsterilized " source " soil in sterilized
" recipient " soil and left them to
incubate for seven weeks. This allowed
microbes to colonize out into the
recipient soil, simulating how microbes
from soil surrounding a cleared-soil
area would colonize back into the
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February 2022

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