WEST LAFAYETTE, Ind. — Farmers with recently planted and
newly emerged corn need to watch their fields for cold injury, even though much
of the damage likely won’t be known until harvest, a Purdue Extension corn
Corn planting has been off to a slow start for Indiana
farmers due to low temperatures and soggy soils. On May 5 the U.S. Department of
Agriculture reported that 20 percent of Indiana’s corn crop had been planted,
compared with a 34 percent five-year average.
Much of what has been planted went into cold soils, meaning
farmers need to watch the crop for injury as it emerges and determine whether
replanting is necessary.
“Where soil moisture was acceptable for planting, some
growers accepted the risks associated with cold soils and corn germination or
initial seedling development and planted corn,” Bob Nielsen said. “Should they
be concerned about the health of their newly planted and, in a few cases, newly
emerged crops? We’ll know for certain come harvest time, but in the meantime, we
can talk about possibilities.”
For newly planted corn, one of the possibilities is what
researchers call “imbibitional chilling injury.” This type of injury happens
within 24 to 36 hours of planting when the kernel absorbs, or imbibes, water and
begins the germination process. When it’s cold, this can cause damage to plant
The symptoms of imbibitional chilling injury include kernels
that are swollen but not showing other signs of germination or slowed growth of
the radicle root or coleoptile — sheath tissue that protects leaves during
emergence — once the initial germination occurs.
Newly planted corn also can suffer non-imbibitional chilling
injury during emergence.
“This type of chilling injury is more closely related to
physical damage to the outer cell tissues that literally cause death of the
plant part or inhibit further elongation of the affected area,” Nielsen
That means injury can include stunting or death of the
seminal root system, deformed elongation of the mesocotyl and either delayed or
failed emergence. The mesocotyl is the part of the plant that connects the crown
and the seed.
During emergence, the mesocotyl extends and pushes the
coleoptile toward the surface. Damaged sections of mesocotyl tissue stop
growing, while healthy tissue continues to grow longer.
“Thus, chilling injury to only part of the circumference of
the mesocotyl results in the corkscrew symptom as the undamaged sections of the
mesocotyl continue to elongate,” Nielsen said.
Corn also can sustain post-emergence damage if aboveground
plant tissue is exposed to cold temperatures. Generally, this type of damage
would require air temperatures 28 degrees Fahrenheit and colder.
If that occurs, Nielsen said damage can range from minor
foliar injury to death of all exposed tissue.
“The good news is that the all-important growing point
region of a young corn plant remains below the soil surface, safe from exposure
to frost, until the V4 to V6 stages of development,” he said. “As long as
temperatures are not lethally cold, simple frost injury usually doesn’t
literally kill such young corn plants.”
Typically, Nielsen said, damaged plants can start to show
recovery in five to seven days, depending on temperatures. Corn plants subjected
to repeat frost events, however, can sustain permanent stunting or death.
But with so little corn in the ground or emerged so far in
Indiana, and with few nighttime temperatures low enough for frost in the last
two weeks, Nielsen said it’s unlikely there has been any aboveground corn
“Only time will tell whether corn planted during the past
few weeks has suffered from the cool soils during germination,” he said.
“Obviously, those early planted fields should be scouted over the next few weeks
for emergence problems.
“Come October, we will know for certain whether this year’s
early planting risk-takers will have won the game or not.”