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Spring Agronomy Reminders
Early Season Stress in Corn
Expected based on recent trend
When Will Planting Begin?…
Quote
“I never went to the Indy 500 as a kid because we were always planting corn”
– Tom Sinclair, USDA Agronomist
(3rd to 4th week of May annually)
Some Common Trends• Faster Planting from Start to Finish
• Significant increase in planter capacity
• Wide Spring Temperature Swings
• Risk of Planting into Colder Soils (<50ºF or less)
• Emergence Risks with Cold/Frost after Planting
• As much as 3 to 4 weeks to emerge in some years
• Damage from Diseases and Insects
• Significant help from seed treatments but not 100%
Factors affecting stand establishment
• Planting Conditions• Tillage Conditions• Planter Functionality• Weather / Climate• Stress Emergence• Seed Quality
Snow After Planting
Good Planting Conditions
Seedling Damage
Poor Stand
Early Season Stress
Why is Corn Emergence Sensitive to Stress?
Tropics vs. North America
ON, Canada, April 29Soil temp 42 °F
Yucatan, Mexico, April 29Soil temp 77 °F
Soil Temperature Effect on Growth & Development
Soil Temperature and Root Growth
Soil Temperature (ºF)
Gro
wth
Rat
e (I
n /
day)
0.0
0.5
1.0
1.5
2.0
2.5
40 50 60 70 80 95
Optimum soil temperature for emergence is ~85 ºF
Soil Temperatures at 4" - Sutherland, IA
30
35
40
45
50
55
60
65
70
75
80
4/1/04 4/6/04 4/11/04 4/16/04 4/21/04 4/26/04 5/1/04 5/6/04 5/11/04
Deg
rees
F
The RisksFluctuating soil temperatures cause stress on seedlings
Data from Iowa State University IEM
Iowa
How close to a “stress event” can I plant corn?
Number of hours with good conditions before imposed
stress emergence (melting ice)
Replant!
Average early root and shoot growth rates for three hybrids under four soil temperatures
ranging from 59 to 95F.
Cold Temperature Damage
Imbibitional Chilling Injury
• Cell membranes are brittle in the cold
• Force of hydration causes membrane rupture
• Leaked cell contents invite pathogens
• Water temperature during initial contact is critical• Most damage occurs during imbibition at < 50°F
Exudate triggers attack by soil fungi& insects
Cell Soil
Membrane
Imbibitional Chilling Injury
Cold Injury Symptoms
Classical cold injury
Cold, temperature swings, herbicide injury
Cold Damage Key Points
• Corn is almost always under severe cold stress • Ideal temperature for emergence is in the high 80’s
• Small variations in seedbed environment or timing of stress can have dramatic effects• Uniformity key for germination and even emergence
• The first hours (24-48 hours) are the most critical• Cold damage risk reduced significantly after this time
• Plant into a warming trend (>50F and rising preferably)