Spudman March 2023 - 11

40 or 50 years on a two-year
rotation. The other part of the
field had not grown potatoes at
all and was unmanaged.
In the field with potatoes, there
was bacteria that could break down
urea. But in the unmanaged field,
those bacteria were barely existent.
Only after a couple of months of
growing potatoes in the new field
did Rosen begin seeing an increase
in those bacteria.
" There's not a lot of overlap in
the microbial communities across
the nation, which I found to be
somewhat surprising working in the
same cropping system, " Frost said.
" I would have thought there would
be a fair amount of overlap in the
microbial communities. "
Another objective is to figure out
if the practices will be economically
viable, impacting either a better
yield or cutting costs for a
grower's management of the field.
Economists are presently looking
at the data.
TIME AND BIOFUMIGANTS
Outreach is another significant
objective. There are a number of
resources on the website (https://
potatosoilhealth.cfans.umn.edu/), as
well as presentations and videos. Given
the scope of the project, the data is still
being computed, but there have been
some interesting developments.
" We did find, at least in Minnesota -
I can't say what happened in all the
other states yet - but we can say
that the biofumigation treatments
tested are somewhat effective, "
Rosen said. " They're not maybe quite
as effective as fumigation, but we
do see some yield benefits to the
biofumigation treatments relative to
no fumigation at all. "
The biofumigant used in the
Minnesota rotation is primarily
mustard, paired with a previous crop
of dried peas and a rye cover crop
following mustard incorporation.
Mustard, when crushed, produces
chemical compounds called
glucosinolates, which have a pungent
odor. Mustard should be chopped or
crushed and incorporated into the
soil, so that the chemical is activated
and released.
The studies revealed a bump in
benefits to biofumigation over not
fumigating at all. It seemed to be more
effective in a three-year rotation than
in the two-year rotation.
The studies revealed
a bump in benefits to
biofumigation over not
fumigating at all.
" The longer rotation you have,
the more benefit you will see, "
said Rosen. This includes reduced
soilborne disease, Frost added.
There's also the idea of shortening
rotation, concerns about soil
degradation, and increased disease
pressure if rotations are shortened.
There was a lot more verticillium
found in the two-year rotation, even
with fumigation, than in the threeyear
rotation.
A BROAD LENS
There is a looming challenge in
regard to potatoes and soil health:
The bottom line with soil health is
minimal soil disturbance.
This study, given its scope,
shouldn't be viewed through one
particular lens. What the team is
looking at is not only the chemical
properties, but also the biological and
physical properties of the soil.
" You can't really just look at one
thing in isolation, " Rosen said.
" They're all related; one thing will
affect the other. "
With so many disparate elements,
there's a lot to consider when moving
forward - from protecting against
verticillium and nematodes using
traditional fumigation or biofumigation,
to changes in the microbiome due to
cropping practices, to the economics of
soil health practices.
" It's a complex thing. There are no
simple solutions, " said Rosen, " but
we're taking it one step at a time. "
Spudman.com 11
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Spudman March 2023

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