corn growth & development - nebraska extension growth... · 2019-03-05 · corn development and...

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Corn Growth & Development

Justin McMechan, Ph.D., D.P.HCrop Protection and Cropping Systems Specialist

Why Care about Growth and Development?

Pesticide

applications

Herbicides

Fungicides

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Pesticide

applications

Critical stages for

management


Pesticide

applications

Critical stages for

management

Diagnosing yield

impacts

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Pesticide

applications

Critical stages for

management

Diagnosing yield

impacts

Corn develops by

GDUs not calendar

days

50°F

86°FMinimum: 50°FMaximum: 86°F

Staging Method Comparison

Leaf Collar Method

Horizontal Leaf Method

Visible on the underside of the

leaf

Leaf opening forms a ”V”

Total leaves up to the last leaf tipped down below

horizontal position

12

3

4

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Late Season Staging

Staging Vegetative Corn

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Germination to Emergence

Radicle

GerminationSeeds absorb

30 -35% moisture

How long can a seed survive without any additional input?

(Just endosperm)

(VE-V1)Leaf Collar

Radicle


30 -35% moisture


(Just endosperm)

Germination to Emergence (VE-V1)Leaf Collar

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Radicle


30 -35% moisture


(Just endosperm)~14 days


Radicle

Coleoptile


30 -35% moisture



Good conditionsoccurs within 1 day of

radicle emergence


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Radicle

ColeoptileMesocotyl


30 -35% moisture



Good conditionsWithin 1 day of

radicle emergence

What stops elongation of the

mesocotyl?


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Seminal roots

Radicle

Coleoptile

Coleoptilar Node

Mesocotyl


30 -35% moisture




radicle emergence


Seminal roots

Radicle

ColeoptileMesocotyl


30 -35% moisture




radicle emergence

Seminal RootSystem


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Seminal roots

Radicle

Coleoptile

Coleoptilar Node

Mesocotyl


30 -35% moisture




radicle emergence

Seminal RootSystem

Gives rise to nodal root systems


3.0 Stage (V2)Leaf Collar

Seminal RootSystem

Maximum Size

Nodal RootSystem

Visible

Placement should be consistent unless planted shallow

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4.5 Stage

Nodal Root Systemis equal to

Seminal Root System

Plant standingdue to combined

strength of leaf sheaths

(V3)Horizontal

Nodal Root System

How many nodal roots will originate from the

stalk over a season?

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Nodal Root System

How many nodal roots will originate from the

stalk over a season?

Approx. 70

6.5 Stage

Primary EarInitiated

~6.5 Stage

(V5)Leaf Collar

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Corn Development and Ear Formation


~6.5 Stage

StalkNode

Ear Shoot

Ears Initiate“acropetally”

Lowest nodefirst



~6.5 Stage

StalkNode

Ear Shoot


Lowest nodefirst

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~6.5 Stage

StalkNode

Ear Shoot


Lowest nodefirst

Tasselinitiated

PrimaryEar



~6.5 Stage

StalkNode

Ear Shoot


Lowest nodefirst

12

13

14

Node

11

Tasselinitiated

PrimaryEar

BasilpetalCRM

103-118

Strachan 2016

Early maturing

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Ear Shoots at 11.5Agropetal Initiation

6 7 8 9 10 11 12 13

3 in

ches

StalkNode

Ear Shoot


Ear Shoots at 11.5Agropetal Initiation

6 7 8 9 10 11 12 13

3 in

ches

8 9 10 11 12 13

9.5

inch

es

Ear Shoots at V18Basilpetal development

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StalkNode

Ear Shoot

PrimaryEar

6.5 Stage Cold Temperature Impacts

Primary ear abortion under chilling temperatures

When applied at:

V6 stage – loss of primary ear

41-50F

(Lejeune and Bernier 1996)


StalkNode

Ear Shoot

PrimaryEar



When applied at:


V3 stage – loss of secondary ears

41-50F


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StalkNode

Ear Shoot

PrimaryEar



When applied at:


V3 stage – loss of secondary ears

41-50F


• Flooding with chilling temp. increased primary ear abortion

Yield Components

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Simulated Hail Machine

Plant Damage and Yield Components

Planting Date

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Planting Date


Planting Date

grams/plant

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Plant Damage and Yield

Corn Yield Components

Ear FormationRapid Plant Growth

Next Slides

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8.0 Stage

All leaves have been initiated

Growing point above soil surface

Knee-high Corn: ~19 inches tall

(V6)Leaf Collar


Yield components occur in sequence

at key stages of plant development

~9.0 stage – row number

Strongly controlled by genetics

Antonio Perdomo

MeristematicDome

Ovules later divide(produce paired rows)

Cheng et al. 1983

V9

KernelRowsEar

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Strongly controlled by genetics

Reduced row number indicates stress ~V7

Antonio Perdomo

MeristematicDome

Ovules later divide(produce paired rows)

V7-V10

V9

Strachan 2004

KernelRowsEar





~13.5 stage – max. potentialkernels

Antonio Perdomo

Antonio Perdomo

V12

V9

Bob Nielson

PotentialKernels

Development

More Less

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~13.5 stage – max. potentialkernels

Antonio Perdomo

Antonio Perdomo

Long-Term Stress: - ovules are sacrificed- usually at the tip

“Blunt Ear Syndrome”

Bob Nielsen

V9

V12

PotentialKernels

Development

More Less

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Other diagnostics

What would a shorter or longer internode tell us?

Internodes


Arrested Ear Development Nonionic Surfactant (13.5-15.0)

Observed within 7 days of application

Variable symptoms: lack of silk development, ovule development ceases

Jones and Westmoreland 1998

Hypotheses:

1. Ethoxy units in surfactant break down to form ethylene oxide (natural plant hormone)

2. Rain water washes surfactant from leaf surface into developing ear, and its taken up in high concentrations

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Arrested Ear Development: 13.5-15.0

From Gary Mungvold, ISU 2007/08

V(n) Stage

Total number of

leaves depends

on the maturity

16-18 leaves for

<100 day corn

18-21 leaves for

100-110 day corn

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Vegetative: Growing Degree Days

Reproductive Growing Degree Days

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VT - Tasseling

All branches of tassel fully visible, extended outward and not held by upper leaves

Not staged based on the presence of pollen

Most susceptible stage to hail damage

Reproductive Stages

Staging is not based on the vegetative appearance of the plant

Focus only on the upper ear to stage the plant & field

Look at kernels in the middle of the ear

Six reproductive stages total whereas soybean has eight

Use number & names when referring to corn R stages Example: R1 = Silking

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R1 – Silking Stage

1 or more silks emerged

Silks Receptive for 5 or

more days

Can grow 1½ in. per day

Pollen fertilization in 24 hrs

after landing

High water use (0.32 in. day)

Timing of Water Stress

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Drought Management

Increased tolerance to

drought

Reduced tassel weight

1967 1991-36%

Duvick etal.2004

Drought Management


drought


Anthesis silking interval (ASI)

ASI

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Drought Management


drought


Anthesis silking interval

(ASI)

Plant Breeding and ASI

Old Hybrids: +2-3 days

(+1wk)

Days

Silking

Bänziger et al. 2000

Drought Management


drought


Anthesis silking interval

(ASI)

Plant Breeding and ASI

Old Hybrids: +2-3 days

(+1wk)

New Hybrids: nearly

same time

BreederSelection

Days

Bänziger et al. 2000

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R2 – Blister Stage

Occurs approx. 10-12 days after R1

Kernel growth begins

following fertilization

Severe stress can easily abort kernels inadequate

carbohydrate supply

Silks Brown

R3 – Milk Stage


Interior resembles “milk”

Minimal decrease in water content since R2; ~80% moisture

Increase in grain dry matter; ~15% of final

Kernel abortion with severe stress

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R4 – Dough Stage


Interior is similar to “dough”

Decreasing water content; ~70% moisture content

Increase in grain dry matter; ~25-30% of final

R5– Dent Stage

Approx. 31-33 days after R1

Kernels are indented at the tops

Decreasing water content 60% moisture

Increase in grain dry matter ~45% of final

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R5– Dent Stage

Liquid(milk)

EndospermSolid

(starch)

SilageNutrient

Loss

R6 – Physiological Maturity

Occurs approx. 64-66 days after R1 Significant time, R5 began: ~33

days

Kernels have reached maximum dry weight and are mature ~35% moisture +/-2%

PM always comes before Black Layer (BL) formation ~28% moisture +/-4%

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When did this happen?

Ear Development Issues

Short Husks

Normal Secondary Ear

Barbell Ears

Multi-ear

Ear SymptomologyMulti-Ear

• Not a new phenomenon• Bonnet 1966 • Nielson 1998-99• Elmore 2006

• Possible Hypothesis• Cold-shock, heat-

shock, wide temp. swings

• Stress to primary ear (silk clipping)

• Genetic factor?

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Short Husks


Barbell Ears

Ear SymptomologyBarbell Ears

• Kernels form at tip or butt of ear, at both locations but the entire length of ear

• Very slender cob• Stress timing: V12 – Tassel?• Chilling temperatures during

ear formation

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Short Husks


Ear Symptomology

Short Husks• Some ears protrude beyond the

husk (hybrid specific)• Potential to aid in dry-down• More severe symptoms

observed in 2016• Stress timing: Before or at

Tasseling (VT)• Husks leaf and ear elongate a

slight different times

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Summary

Staging is critical component of

many management decisions

Corn yield components are set at

different times during development

Can be used as a diagnostic for when

things happened

Acute vs. Chronic impacts on yield

components

Thank You

What questions do you have?

corn growth & development - nebraska extension growth... · 2019-03-05 · corn development and...

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