As spring arrives in south Georgia, people stream outdoors to
enjoy the warm days.
Peanut seeds, though, may find it still too chilly to venture
out.
“Peanuts are very sensitive to soil temperature,” said John
Beasley, an
agronomist with the University of Georgia Extension Service.
Georgia peanuts are a $400 million crop. To reach the full
value of the crop, farmers
have to time their planting just right. Sparse stands of
peanuts, Beasley said, are almost
always due to poorly timed planting.
But as the weather warms, some farmers start planting,
whatever soil temperatures may
be. Peanuts don’t grow in air, though, and soil warms up much
more slowly than air.
"The four-inch soil temperature needs to be at or above
65 degrees for three or
more straight days for minimum peanut seed growth," Beasley
said. "Peanut seeds
must be in 65-degree soils to germinate and emerge
quickly."
During the weekend of March 16-18, the air reached a balmy 79
degrees. But the soil
hovered around 60 degrees — too cool to safely plant
peanuts.
The problem for overeager farmers is serious.
Seed companies coat their seeds with fungicides to protect
them during the first vital
growing days, Beasley said.
The fungicides can protect the seed for two to three weeks in
dry weather. That usually
allows plenty of time for the seed to germinate and emerge from
the soil.
"Until that seedling emerges and begins producing the
energy it needs through
photosynthesis, the seed sustains it," Beasley said. If it
doesn’t emerge fast, the young
plant faces the risk of running out of energy from the seed.
If diseases attack or destroy the seed before the young plant
emerges, the plant can
die or be stunted from lack of nutrients.
Farmers can rely on weather service temperature readings from
a weather station near
their farm. But Beasley said it’s easy to take a reliable
reading in the field where it
needs to be measured.
"This can make or break growers, so accurate measurement
where it counts is
critical," he said. Beasley said any thermometer that
registers 65 degrees and is
long enough to insert into the soil will work. So special,
costly thermometers aren’t
required.
Some farm supply dealers may have thermometers already marked
to a four-inch depth,
making the process one step easier.
Beasley tells farmers to take soil around noon, leaving the
thermometer in the soil for
about two hours. "It’s safe to assume that’s an average
temperature for that
soil," he said.
When the lowest temperature from several spots in a field is
above 65 degrees for three
or more days, the soil is warm enough to plant peanuts.
But Beasley warns farmers to watch the forecast even then.
"If a cold front or a
cold rain is on the way, it could dramatically reduce soil
temperatures around
freshly-planted seed," he said.
Sandy, loose soil warms and cools quicker than heavier clay
soils, he said. So
clay-soil fields could stay warm through a short cool spell
while a sandy soil would cool
off.
Most fields contain both sandy and clay soils in different
areas. Beasley said
measuring and recording temperatures is the easiest way to be
sure the field is warm
enough for planting.
"Seed is the biggest investment besides pesticides in
peanut production,"
Beasley said. "It doesn’t make any sense to plant them into
undesirable
conditions."
