July 2022 - 13

NEW TECHNOLOGY PROVIDES FIRST-EVER
SNAPSHOT OF FUMIGANTS' IMPACT ON SOIL HEALTH
S
oil fumigation is highly effective at
managing soil pests that cause crop
disease. However, it is regularly accused
of doing more harm than good to overall
soil biology. Advances in genetic sequencing
technology can now provide a detailed snapshot
of how fumigation actually changes bacterial and
fungal populations in agricultural soil, and the
close-up look is surprising many.
Regulators and even some scientists
have alleged fumigation 'sterilizes' the soil,
indiscriminately killing all microbes including the
populations critical to soil structure and fertility,
nutrient cycling and more. In fact, new data
proves that belief is incorrect for the fumigants
chloropicrin and 1,3-D (TELONETM
).
Until very recently, determining a fumigant's
impact on soil was guesswork: 95% of soil
organisms couldn't be isolated and grown in the
laboratory - and therefore couldn't be quantified.
Now, however, genetic sequencing technology
can isolate and analyse ribosomal RNA, allowing a
clear and complete description of a soil sample's
biological profile.
" We can finally stop guessing at what's in our
soil. For roughly $250 per sample, anyone who is
interested can determine exactly what's in their
soil to a level of precision that was never possible
before, " says Dr. John Washington, Director of
Operational and International R&D for TriEst
Ag Group. " It's a kind of genetic barcoding: the
technology can identify every organism group
and their relative amounts. "
Microbiome analysis shows that soil-applied
chloropicrin and 1,3-D alter the soil biology in
important but non-destructive ways. In fact, over
the crop season, the soil's total biome returns to
much the way it was prior to fumigation, except
for some fascinating changes. Each fumigant has
distinct effects. For example, 2021 trials showed
Trichoderma, a well-known group of beneficial
fungi, increased 20-100-fold in plots treated with
chloropicrin. Population benefits lasted the entire
season, and even extended into the next season
in some settings, since Trichoderma overwinters
in northern tree crop soils. The same trials
showed Trichoderma did not increase in plots
treated with 1,3-D alone, but did increase in plots
treated with commercial formulations containing
both chloropicrin and 1,3-D.
Beneficial root-colonizing bacteria Bacillus
and Pseudomonas, which produce plant-active
hormones, increase dramatically with both
fumigants. Saprophytic bacteria and fungi, which
live off non-living, decaying organic matter,
also increase after fumigation. Saprophytes
play major roles in soil nutrient cycles, and also
support soil structure, promote plant growth and
are involved in natural, biological control of some
soil-borne pathogens.
While these and other specific bacterial
population findings are new, understanding
of chloropicrin and 1,3-D's soil health benefits
is supported through research conducted by
scientists from around the world.
In late December 2021, University of Florida
plant pathologists released a meta-analysis - a
comprehensive review of multiple research
studies by other researchers - analyzing
the impact of fumigants on non-target soil
microorganisms. Their report concluded that,
while fumigation can decrease biological
abundance and diversity by 10 to 50%
immediately after application, the effect
is temporary: according to their findings,
populations rebounded within 4-6 weeks
following fumigation with chloropicrin/1,3-D
mixtures.
In 2019, Phytobiomes Journal published
research by Colorado and Oregon State
researchers showing that fumigation with 1,3-D
increased the population of Enterobacteriaceae,
a family of bacteria that include species
that specialize in nutrient cycling, while
simultaneously decreasing the population
of pathogenic fungi such as Pythium and
Verticillium. The impact of beneficial microbes
can be significant, with visible plant health noted
inside of a single season and long-term benefits
achieved over multiple applications of 1,3-D.
In 2017, applied and industrial microbiology
journal AMB Express published results from
a three-year soil microbe study conducted
collaboratively by Dutch and Chinese researchers.
ADVERTISEMENT | © 2022 TriEst Ag Group
The study described soil fumigation as offering
a clear " legacy effect " : a strong and sustained
increase in the relative abundance of the
beneficial microorganisms, Actinobacteria and
Saccharibacteria.
Fungal and bacterial diseases can have a major
impact on crop marketability and profitability.
For example, in potatoes, common scab (brown
lesions on a potato's skin) can reduce the value
of the crop by as much as 20 to 50%. Because
crop production utilizes resources like water and
fertilizer, significant disease-induced crop losses
translate in effect to poor ecological stewardship,
and bite deeply into both sustainability and a
farm business' total returns. Ultimately, better
managing loss is exactly why growers turn to
chloropicrin and 1,3-D, as they are the only tools
available that decrease soil pests and diseases
without compromising other aspects of soil health.
" Research relating to chloropicrin and 1,3-D's
impacts on soil's microbial populations is really
interesting because it contradicts mainstream
dogma and misunderstandings about the soil
health effects of fumigants. Building from a
more accurate understanding of what is actually
happening in the soil, we'll be positioned to
make further gains in agronomy, sustainability
and profitability. We're now ready for much
more productive and interesting conversations
because we better understand the true dynamics
of biological soil health and how to improve it
further, " says Washington.
" The new genetic sequencing technology
shows that soil fumigation with chloropicrin or
1,3-D doesn't destroy the soil biome; it actually
supports it. "
Chloropicrin products are federally Restricted Use
Pesticides. TELONETM
read and follow label directions.
Trademark of the Dow Chemical
Company ( " Dow " ) or an affiliated company of Dow.
TELONETM
is a federally Restricted Use Pesticide. Always
July 2022

Table of Contents for the Digital Edition of July 2022
