May/June 2023 - 23

PLANT & SOIL HEALTH
levels significantly compared to the
non-treated control. Steam plus
quicklime brings high average soil
temperatures compared to steam plus
sodium peroxide and steam by itself,
Volk said.
" The treatment effect we saw on
pathogen levels was that quicklime
plus steam controlled for pythium
species more effectively than the
components by themselves, " Volk said.
" However, we did not see this effect
when we looked at the combination
of sodium peroxide and steam. It did
not control pythium species more
effectively than steam on its own. "
Ending pathogens
Researchers found that regardless
of treatment, pathogen levels tend to
decrease as average temperatures
increase. Pathogens were controlled
once 131 or 140 degrees Fahrenheit
temperatures were reached. An
average temperature of 133 degrees
for 30 minutes was able to effectively
control for pythiums species,
Volk said.
In weed control, a relationship
between temperature and weed
germination was observed, particularly
for nutsedge tubers. Steam plus
sodium peroxide and steam plus
quicklime effectively controlled
germination. " As average temperature
increases, that average percent of
germination decreases, " Volk said.
" There seems to be this point that once
you exceed a certain temperature, the
percent of germination reaches zero. "
In Volk's research, that averaged
158 degrees.
The study also found that high
soil pH can significantly affect
microorganism populations. As pH
increases, microorganism populations
decrease, but the process takes a long
time, Volk said.
Overall, quicklime does better than
sodium peroxide in improving field
steam application efficiency.
" Quicklime is more promising
because it has more positive effects
on both pathogen levels and weeds in
comparison to sodium peroxide, which
Studying soil temperature and pathogen levels during steam treatment,
NC State researchers found pathogen levels tend to decrease as average
temperatures increase.
primarily was just able to control for
weeds, " Volk said.
Quicklime was found to maintain
high temperatures at farther distance
points from steam injection compared
to other treatments, Volk said.
As a proof of concept study, Volk
said more work needs to be done
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May/June 2023

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