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Published 9 Apr 2007
Cold Temperatures & Early Planted, Emerged Corn
R.L. (Bob) Nielsen
Agronomy Dept., Purdue Univ.
West Lafayette, IN 47907-2054
Email address:
Average daily low air temperatures over the past three to four mornings have ranged from 22F to
28F throughout a large area of Kentucky
and southern areas of Indiana.
This recent spate of unusually cold temperatures raises questions about injury
to early-planted corn and the possibility for the eventual need to replant damaged
stands of corn. The concern lays not
so much in above-ground frost injury to exposed leaves, but to truly lethal
cold-injury to the plants’ growing points below ground.
Conventional wisdom (or agronomic legend) says that corn seedlings
will tolerate air temperatures down to about 28F before serious injury occurs.
One caveat to this statement is that soil temperature typically changes less
dramatically than air temperature, thus delaying the onset of cold-injury to
the plant’s growing point region while it remains below ground. Moist soil will
change temperature more slowly than dry soil, thus “insulating” the growing
point further from the onset of cold-injury.
Nevertheless, the risk remains for injury to early planted
corn in southern Indiana and throughout
Kentucky from these very cold
temperatures in recent days. The key to the replant decision-making process
will be evaluation of the health of the growing point region (Nielsen,
2004a).
Depending on the severity of damage, visual symptoms may not
be evident for several days to a week after the occurrence of the potentially
lethally cold temperatures. Don’t worry so much about damage to above-ground
leafy tissue as to the potential for injury to the below-ground growing point.
Appearance of the growing point region plus visual evidence (or not) of fresh
leaf tissue from the damaged above-ground whorl will be the key diagnostics
for assessing condition of the stand of corn.
Corn planted, but not yet emerged may eventually exhibit what
is often termed “cork-screwed” elongation of the mesocotyl or coleoptile during
emergence in response to chilling injury to the cell tissue of those plant parts
(Nielsen,
2004b). The worst case scenario in this situation is failure of affected
seedlings to emerge; instead leafing out underground.
As with many replant decisions, patience is the key word (Nielsen,
2006). Damaged fields usually need to be given several days to a week to
begin their recovery before one can confidently assess their condition and the
potential need for replant. The Univ.
of Kentucky recently published several
articles on corn replanting issues (Corn
& Soybean News, Apr 2007)
Related References
Corn & Soybean News. Apr 2007. Corn Replanting Issues. Univ.
of Kentucky. [On-Line]. Available
at http://www.uky.edu/Ag/CornSoy/cornsoy7_5.htm.
(URL verified 4/7/07).
Nielsen, RL (Bob). 2004a. Growing Points of Interest. Corny
News Network, Purdue Univ.
[On-Line]. Available at http://www.kingcorn.org/news/articles.04/GrowingPoints-0507.html.
(URL verified 4/9/07).
Nielsen, RL (Bob). 2004b. Corkscrewed Corn Seedlings. Corny
News Network, Purdue Univ.
[On-Line]. Available at http://www.kingcorn.org/news/articles.04/Corkscrew-0501.html.
(URL verified 4/7/07).
Nielsen, RL (Bob). 2006. Corn Replant Decision-Making. Corny
News Network, Purdue Univ.
[On-Line]. Available at http://www.kingcorn.org/news/articles.06/Replant-0515.html.
(URL verified 4/7/07).
For other information about corn, take a look at the Corn Growers' Guidebook
at http://www.kingcorn.org.
©2007, Purdue University, all rights reserved. It is the policy of the
Purdue Agronomy Department that all
persons shall have equal opportunity and access to its programs and facilities
without regard to race, color, sex, religion, national origin, age, or disability.
Purdue University is an Affirmative Action
employer. This material may be available in alternative formats.
End of document
