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)