July 2021 - 16

PLANT & SOIL HEALTH
Tracking nitrate in farm fields focus of researcher
By Rachel Schutte
Soil Science Society
For years it's been relatively easy to
measure pollution from, say, a factory.
At a factory, there might be just one
pipe of waste to measure. Easy enough.
But what about a farm? We might not
typically think of farms as sources of
pollution, but they can have big impacts
on the land over time. Unlike at a
factory, the waste filters slowly through
soil across the whole plot of land.
This waste - excess nutrients
from fertilizer - can eventually
reach groundwater. If too much
nitrogen enters groundwater, it can
be dangerous to drink. In the form
of nitrate, this nitrogen is especially
bad for infants. The groundwater can
eventually feed lakes or streams. There,
the nitrate can cause algae blooms and
dead zones without oxygen.
" We see these dead zones annually
over a large region near the mouth of
the Mississippi, in the Gulf of Mexico, "
Thomas Harter said.
Harter, a member of the Soil Science
Society of America, is trying to solve
one of the most complex puzzles in
farming: how to track nitrate as it
moves through farm fields.
One of 20 monitoring wells across the almond orchard test site, allowing researchers to monitor the levels of nitrate reaching groundwater
from the soil above. Photo: Thomas Harter
His research was recently published
in Vadose Zone Journal, a publication
of the Soil Science Society of America.
Scientists have tried for years to
predict how nitrate will flow from
the surface into groundwater. That
information can help farmers balance
fertilizing their crops with protecting
the water they and others rely on, but
there are many challenges. The types
of soil, crops and fertilizers can all
affect this slow process.
So Harter and his team designed
one of the most detailed studies yet.
Across a single 140-acre California
almond orchard, they gathered 20
deep soil samples and installed wells
to measure groundwater. Few studies
have been so detailed across such a
small plot of land.
They found that a complex quilt
of different soils lies underneath the
almond orchard. These different soil
types made it very hard to predict how
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July 2021

Table of Contents for the Digital Edition of July 2021