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Corn Planting
4/27/2005
Ron F. Meyer
Area Extension Agent
(Agronomy)
Colorado State University Extension
Golden Plains
Area |
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Since soil temperature, stand establishment and uniform emergence
are all key considerations when attempting to determine an optimum corn
planting window, early plantings are generally discouraged when significant
acreages are involved. Agronomy professionals agree that the optimum corn
planting window will be related directly to a consistent soil temperature of
around 50 to 55° F at the two-inch soil depth. Traditionally, these
consistent soil temperatures occur between the third week of April through the
first week of May. Since cool soils through mid-April often result in a
lengthy germination period, corn emergence can often times take over three
weeks from the time of planting to full stand establishment. Table 1
outlines the approximate days to seedling emergence based on various,
consistent, soil temperature ranges:
| Table 1: Days to emergence based on soil
temperature. |
| Soil Temperature . . . . . Approximate Days to Corn
Emergence |
50° F.................................... 25
– 20 Days
55 - 60° F............................ 14 – 10 Days
65 - 70° F.............................. 8 – 5
Days
75 - 80° F.............................. 4 Days |
Crop Observations/Management
Suggestions
Under cold weather conditions or fluctuating soil
temperatures, the coleoptile (shoot) still emerges from the seed, but rather
than growing upward towards the soil surface, it twists or curls around the
seed. The unusual growth pattern of the coleoptile is in response to cold
soil conditions; this type of growth alone is usually not cause for
alarm. Once soil temperatures improve, the coleoptile will
“right” itself and grow towards the surface, where it splits open
when exposed to sunlight, allowing the first leaves to emerge.
Corn may
leaf out underground for a number of reasons. A cloddy seedbed or
improper closure of the seed furrow may allow light to penetrate below the soil
surface. If light reaches the emerging coleoptile (spike) underneath the
surface, it may rupture, causing the leaves to unfurl. Cold soils and
compacted and/or crusted soils can also lead to leafing out underground.
Some herbicides occasionally magnify the corkscrew problem with the soil
conditions mentioned above.
Once corn is emerged other issues can
express themselves. Purple Corn Syndrome shows up in a handful of
cornfields nearly ever year. This purple seedling color results from the
expression of genes for anthocyanin pigment formation. Most corn hybrids
contain 5 of the necessary 8 genes required to produce this purple color, while
the other 3 genes are present in only certain hybrids suggesting this attribute
is a “genetically inherited” trait more prominent in certain hybrids
over others.
Since several of these genes are cold sensitive, overnight
temperatures in the 40s with daytime highs in the 60s are often sufficient to
trigger a purpling effect on corn leaves. Since these temperature
sensitive genes are only expressed in seedlings prior to the six-leaf stage of
growth, this early developmental stage often coincides with the same period
most likely to have lower temperatures. Corn usually outgrows the
condition by the time it is 12 inches tall. This occurs quickly if
weather remains conducive for rapid growth or slows if conditions remain cool
enough to retard root and shoot growth.
Realizing that cool
temperatures, not the purple pigment itself, results in slow plant growth is
important. Extensive research has been conducted on purple corn with no
negative yield implications observed.
Source: Alan Brax, Pioneer
Hi-Bred Intl |
Page Created and Maintained by: Perry D. Brewer, Area
Extension Agent (Technology Education/Youth)
5/5/2005 |
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