Lee and Herbek, Grain Crops Extension © 20061 Corn Growth and Development Chad Lee Grain Crops...

Lee and Herbek, Grain Crops Extension © 2006 1

Corn Growth and Development

Chad LeeGrain Crops Extension Specialist859-257-3203 ● [email protected]

www.uky.edu/Ag/GrainCrops/

Lee and Herbek, Grain Crops Extension © 20062

Goals for Today

• Growth and Development

• Key Management Issues

• Scouting Techniques

• Biotech Options


Corn Growth Stages

• Vegetative (V)

• Reproductive (R)

How a Corn Plant Develops, Special Report No. 48Iowa State Universityhttp://maize.agron.iastate.edu/corngrows.html


Vegetative Stages Reproductive Stages

VE emergence R1 silking

V1 first leaf R2 blister

V2 second leaf R3 milk

V3 third leaf R4 dough

V(n) nth leaf R5 dent

VT tasselingR6 physiological

maturity

* When staging a field of corn, each specific V or R stage is defined only when 50 percent or more of the plants in the field are in or beyond that stage.

http://maize.agron.iastate.edu/corngrows.html


“Spiking” Corn


VE - Emergence


http://maize.agron.iastate.edu/corngrows.html#stages

V1 – One Visible Collar


Corn Growth Stages: Vegetative

V33 Collars

V66 collars

V1212 collars

V1515 collars

VTtassel


Corn Growth Stages

V33 Collars

Nodal roots active.

Growing point below ground.

V66 collars

Growing point above ground.

Tassel and ear development starting.

V1212 collars

Ear size, kernel size and kernel number being determined.

Limits on water and/or nutrients will reduce yields.


V3 – Three visible collars


V3

Root hairs begin to form on Nodal Roots.

Seminal Root growth has basically stopped.

Growing point is below the soil surface.

Frosts on the surface will not kill the plants.

Freezing soil temps will kill the plant.

Flooding can kill plants.


V6

Tassel development has started.

Ear shoot formation has also started.


To be certain about V-stages beyond V6:

Split the entire stalk (from the tip to the roots) in half with a knife.

The first five nodes will be clustered near the bottom of the stalk and the 6th node will be very close to the soil line.

Count nodes above the 6th node to determine how many nodes are present.

The total number of nodes equals the V-stage of the plant.

For example 7 nodes = V7 corn.

V6 Leaves start to tear off the plant


V6

Nodal Root System is the primary root system for nutrients and water.

Growing point is above the ground.

Ear shoot.


V6

Premature Tassel


V9


V9Growth rate rapidly increases. Greater demand for nutrients and water.

Ear shoot.

Ear shoot.

Ear shoot.

Growing point.


V12

Both kernel size and kernel number are being determined.

Any limits on water or nutrients at this phase will drastically impact yields.

Earlier maturing hybrids will pass through this phase faster than later maturing hybrids.


Corn Growth Stages

V1515 collars

Rapid growth, about 10 to 12 days before silking.

Most critical stage for yield determination.

Most sensitive to stress.

VTtassel

Last tassel branch is visible but prior to silking.

Complete leaf loss will cause nearly 100% yield loss.


V15About 10-12 days from silking. Entering the most critical stage for yield determination.

The plant is most sensitive to water and/or nutrient stress at this stage.

Irrigation- the 4 weeks around silking are the most critical.


V15Ear shoots near the top of the plant are starting to out-grow ear shoots lower on the plant.

Lower part of plant Upper part of plant


V18


V18



V18



VT


VT - Tassel

Occurs when last branch of tassel is visible but before silks emerge.

Most susceptible to hail damage at this stage.

Complete leaf loss at VT will result in little to no yield.


Pollen shed


Corn Growth Stages: Reproductive

R1Silking

R2Blister

R4Dough

R5Dent

R6Physiological Maturity


Corn Growth Stages

R1Silking

N and P uptake are rapid.

About 50% of total N is taken up after R1.

K uptake is nearly complete.

Water needed for pollination.

Pollination occurs.

R2Blister

Ear size nearly complete.

Silks begin to dry out.

A miniature corn plant is being formed in each fertilized kernel.


R1- Silking


R1 - Silking

Silks starting to emerge.N uptake is rapid.

P uptake is rapid.

K uptake is nearly complete.

Watch for corn borer feeding.

Moisture is needed for pollination.


R1 - Silking

Cob materialPremature kernel

Two to three days are required for all silks on an ear to be pollinated.


R2 - Blister

An miniature corn plant has started to develop within the premature kernel.

Ear size is nearly complete.Fertilized silks are starting to dry out.


R3 - Milk

Kernels are becoming yellow on the outside.Silks are dry. Kernels are at 80% moisture.Stress becomes less of a factor as kernels start to dry down.


Corn Growth Stages

R4Dough

Kernels have accumulated ½ of total dry weight.

Five leaves have formed in the kernel.

R5Dent

Most kernels have dented and are near 55% moisture at start.

Starch layer has formed and progresses down the kernel.


R4 - Dough

Fluid in the kernel is becoming a consistency similar to dough. (70% moisture)Almost ½ of the dry weight has been accumulated.Five embryonic leaves have formed in the kernel. These will be the first five leaves of a new plant as it emerges next year.


R5 - Dent

Most of the kernels have dented on the top. Most kernels are about 55% moisture at the start of R5.A starch layer has formed and begins to progress down the kernel.A frost will stop dry matter accumulation and reduce yields.


Corn Growth Stages

R6Physiologica

l Maturity

Blacklayer has formed at bottom of kernel.

Kernel is about 30 to 35% moisture.

For safe storage, needs to dry to 13 to 15% moisture


R6 – Physiological Maturity

Kernel is about 30 – 35% moisture.

Kernels need to be at 13 to 15 % moisture for safe storage.


R6 – Physiological Maturity

Blacklayer


Corn Planting Dates in Kentucky

Corn should be planted by:

Far Western KY May 1

Western-Central KY May 10

Eastern KY May 15

Plant an earlier-maturing hybrid if corn planting is delayed after:

June 5

A 1% yield loss per day can be expected in corn planted after:

May 10-15


Corn: Seeding Rates

Table 3. Recommended corn seeding rates for Kentucky.

Seeding rate* (seeds/acre)

Grain 22,000 - 30,000

Silage 24,000 - 30,000

Irrigated 26,000 - 32,000* Range depends on potential yield of soil ranging from less than 100 bu/ac for the low range to more than 200 bu/ac for the high range.


Biotech Tools for Corn Insects

Bt Corn– YieldGard Corn Borer(Cry1Ab)

– YieldGard Rootworm (Cry3Bb1)

– YieldGard Plus (Cry1Ab+Cry3Bb1)

– Herculex I (Cry1F)

– Herculex RW (Cry34Ab1/Cry35Ab1)

– Herculex Xtra (Cry1F+Cry34Ab1/Cry35Ab1)

– Agrisure CB (Cry1Ab)

– Agrisure RW ? (Cry3A)

– Agrisure CB/RW ?


Biotech Tools for Corn Weeds

• Roundup Ready genes– GA21 – “Roundup Ready”

• Applications from VE to V8 or 30 inches, whichever occurs first, up to 1.0 lb ae glyphosate/acre, depending on herbicide label (2 pt/A of 3 lb ae/gal formulation – Roundup Original)

– NK603 – “Roundup Ready 2” • Applications from VE to V8 or 30 inches, whichever comes

first, up to 1.12 lb ae glyphosate/acre, depending on herbicide label (3 pt/A of 3 lb ae/gal formulation – Roundup Original)

• Drop nozzles from 30 to 48 are allowed


Biotech Tools for Corn Weeds

• Liberty Link– T25 - Corn (PAT, BAR) – Combined with Herculex (Cry1F)

• Used as a marker gene for the Cry1F event


Corn, Narrow vs. Wide Row Widths

Location

1-TX 2-SC 3-KY 4-IL 5-MO 6-PA 7-IA 8-IA 9-MI 10-MI 11-MI 12-MI 13-WI 14-WI 15-MN 16-MN 17-MN 18-MN 19-MN 20-MN

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Narrow Row Corn


Estimating Corn Yield

(kernels per ear) x (ears per acre) / (kernels per bushel) = (bushels/acre)


Estimating Corn Yields

• Simplest (least accurate method)– Count number of kernels– Multiply that number by 0.300

Using 0.300 assumes 1) 27,000 ears per acre 2) 90,000 kernels per bushel

1


Estimating Corn Yields

Ears/Acre Large Kernel Size(70,000

kernels/bushel)Multiplier

Medium Kernel Size(90,000


Small Kernel Size (110,000


22,000 0.314 0.244 0.200

23,000 0.329 0.256 0.209

24,000 0.342 0.267 0.218

25,000 0.357 0.278 0.227

26,000 0.371 0.289 0.236

27,000 0.386 0.300 0.245

28,000 0.400 0.311 0.255

29,000 0.414 0.322 0.264

30,000 0.429 0.333 0.273

34,000 0.486 0.378 0.309

AGR-187: Estimating Corn Yields

Including ears/acre as a factor and kernel size as a factor.



Row Width (inches)Feet of row needed to equal

1/1000th acreMultiplier to Equal One

Acre

15 34 feet 10 inches 1,000

20 26 feet 2 inches 1,000





Measuring 1/1,000th Acre




More accurate stand measurements.

Row Width

(inches)

Measured Row Length

(feet)

Total Measured Area (ft2)

Number of Ears per

Measured Area

Number of Ears per Acre

30 50 125 40 13,939

60 20,909

65 22,651

70 24,394

75 26,136

80 27,878

85 29,621

90 31,363

100 34,848



Estimating Early Season Stand Losses

Table 2. Grain yields for various planting dates and population rates, expressed as a percent of optimum planting date and population rate (uniformly spaced within row).

Planting date

Plants per acre at harvest

12,000 14,000 16,000 18,000 20,000 22,500 25,000

(% of optimum yield)

April 15 70 76 81 85 88 91 93

April 20 72 78 83 87 90 93 95

April 25 75 81 86 90 93 96 98

May 1 77 83 88 92 95 98 100

May 6 78 83 88 92 95 98 100

May 11 77 83 88 92 95 98 99

May 16 75 81 86 90 93 96 98

May 21 73 78 83 87 91 94 95

May 26 69 75 80 84 87 90 92

May 31 64 70 75 79 82 85 87

June 5 59 64 69 73 77 80 81

June 10 52 58 63 67 70 73 75

Data from National Corn Handbook


Keys to High Yields

1. Good genetics

2. Maximize days suitable for growing

3. 90 to 95% light interception at silking (R1)

4. Adequate nutrients and water to complete plant growth and seed fill


Keys to High Yields

• Good genetics– Good yield potential– Good stress tolerance– Good defense genetics


Keys to High Yields

• Maximize days– Maturity group– Stress tolerance– Planting date


Keys to High Yields

• 90 to 95% light interception at silking (R1)– Row spacing and population– Planting date– Hybrid Maturity


Keys to High Yields

• Adequate nutrients and water to complete growth and seed fill– Soil pH – Adequate N, P, K, Zn– Precipitation– Water infiltration– Water availability


Slats on a Barrel

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Corn Growing Degree Days

• Each day has a slightly different average temperature.

• Temperature affects corn growth rate. • Attempt to relate temperature to corn growth rate.

• Corn Growing Degree Day• Base 50° F• Max 86° F• Min 50° F



• Corn Growing Degree Day• Base 50° F• Max 86° F• Min 50° F

• Example 1: – 74° F average daily temperature– 74 – 50 = 24 GDD

• Example 2:– 90° F average daily temperature– 86 – 50 = 36 GDD



Corn Maturity (Days) GDD85 to 100 2100 – 2400

101 to 130 2400 – 2800131 to 145 2900 – 3200

Growth Stage GDDV2 200V6 475

V12 870VT 1135R1 1400R6 2700

GDD Requirements of a 2700 GDD Hybrid

From NCH-40 Growing Season Characteristics and Requirements in the Corn Belt. National Corn Handbook.


Planting Date and GDD

Planting DateGDDAs of 06/26/05

Difference From First Planting

April 20 1155 ---May 3 1029 126May 18 825 330May 31 596 559June 15 281 874

Hybrid: DKC67-91: 119 CRM, 3000 GDD to Black Layer

From University of Kentucky Ag Weather Center: http://wwwagwx.ca.uky.edu/Growing Degree Day calculator: http://wwwagwx.ca.uky.edu/cgi-bin/cropdd_www.pl


Planting Date and GDD

Planting DateGDDAs of 07/11/05

Difference from First Planting

April 20 1503 ---May 3 1377 126May 18 1173 330May 31 944 559June 15 629 874

Hybrid: DKC67-91: 119 CRM, 3000 GDD to Black Layer

From University of Kentucky Ag Weather Center: http://wwwagwx.ca.uky.edu/Growing Degree Day calculator: http://wwwagwx.ca.uky.edu/cgi-bin/cropdd_www.pl


Date of Planting – Corn and Grain Silage

1976 - LexingtonDate planted Relative Yield Ratio

Maturity Bu/A T/A @ 35% Ear:Forage

April 20 Full 180 27.2 56:44

May 6 Full 177 25.8 59:41

May 21 Full 166 23.4 60:40

May 31 Full 144 19.9 60:40

June 10 Full 112 16.4 57:43

June 10 Early 128 18.1 60:40

June 29 Early 64 11.2 48:52

May 20 S 77 18.2 42:58


Effect of Tillage and Planting Date on Corn Yield

4-avg. (1979-1982)

Planting Date

Conventional No-Till Avg.

Corn Yield (bu/A)

Early May1 121 121 121

Mid-May 102 124 113

Early June 86 102 94

Avg. 103 116

1 Three-year avg. only. 1979 data missing for Early May.


Corn Planting Depth and Planting DatePlanting Depth

Planting Date

April 13 May 2

(inches) % StandDays to Emerge

% StandDays to Emerge

1 85 10 93 9

2 77 15 98 11

3 76 18 92 12

4 73 21 89 13


Germination Temperature for Corn

• 50 OF at a 2-inch depth for three or four days is excellent.

• Soil temperature at 50 OF at 7:00 am or 55 OF at 1:00 should ensure that temperatures are suitable for germination and growth.


Population Effect on Corn Yields

(Hardin County, Kentucky, 1972-76)

Population Corn Yield (Bu/A)

Plants/A No-Till Conventional

14-18,000 133 114

20-23,000 148 119

26-28,000 158 128

Average 146 120


Effect of Row Width and Plant Population on Corn Yields

(8 location average)

Yield (bu/A)

Row Width 20 inch 170 ab*

30 inch 175 a

36 inch 169 b

Plant Population 20,000 164 a

26,000 171 b

30,000 178 c

*0.10 level for row width, 0.05 level for population.


Row Width Effect on Corn Yields

(Hardin County, Kentucky)

Row Width Corn Yield (Bu/A)

(inches) No-Till Conventional

1972-1974

19 161 137

38 162 133

1975-76

30 109

38 116


Corn Hybrid and Population Effect on Grain Yield

Plants/A Yield (bu/A) Yield (bu/A)

Irrigated Rainfed Irrigated Rainfed

Pioneer 3160 B73 x PA91

20,000 155 139 163 152

28,000 192 132 169 134

36,000 176 130 189 133

DeKalb XL32AA A635 ---

20,000 136 121 119 119

28,000 167 136 131 129

36,000 172 130 133 130

Population resulting in highest yield varied across hybrids and water regimes.


What determines crop row width?

Fig. 2 The relationship between hybrid yield at different plant densities and year of release. Data were obtained from field experiments conducted at three locations in central Iowa in 1994.

Duvick D.N., and K.G. Cassman. 1999. Crop Science 39:1622-1630


Row Width Effect on Corn Grain Yield

(Non-Irrigated)

Yield (bu/A)

30 inch 36 inch Difference

1979 154 142 + 12

1980 122 120 + 2

1981 152 155 - 3

1982 116 130 - 14

Average 136 137 - 1


Row Width Effect on Corn Grain Yield

(Irrigated)

Yield (bu/A)

30 inch 36 inch Difference

1979 199 176 + 23

1980 143 141 + 2

1981 163 156 + 7

1982 175 177 - 2

Average 170 162 + 8


Corn Hybrid, Row Width and Plant Population

Summary Across Years

HybridYield (bu/A)

Row WidthYield (bu/A)

Pioneer 33Y18 155.4 a 20 inch 148.4 a

So. States SS828 143.9 b 30 inch 150.9 a

Plant PopulationYield (bu/A)

24,000 148.7 a

28,000 151.5 a

32,000 148.7 a


Recommended Corn Seeding Rates(Greatest Limiting Factor to Corn Yield)

Plants / Acre

Rainfed Grain Corn

(No-Till and Conventional)22,000 – 30,000

Irrigated Grain

(No-Till and Conventional)26,000 – 32,000

Silage 24,000 - 30,000

From ID-139: A Comprehensive Guide to Corn Management in Kentucky.


Uneven Corn Stands Cost Money

• Good stands = 2 inch deviation– Example 26,000 seeds on 30 inch row– Equals 1 plant every 8 inches– Good stand is 6 to 10 inches apart

• 2.5 bushel lost for every 1 inch increase in deviation– 3 inch deviation = 2.5 bushel loss– 5 inch deviation = 7.5 bushel loss


Effect of Emergence Delays on Corn Yield

• Uneven emergence of:– 10 days = 6 – 9 % loss– 21 days = 10 – 22% loss

– 7 days = 5.5% loss– 14 days = 13.2% loss

• Primary Causes: – 1. Soil Moisture– 2. Poor soil-to-seed contact

(Wisconsin and Illinois research)

(Minnesota research)


The major factor influencing vegetative development in grain

crops is:

TEMPERATURETEMPERATURE

Ideal Growing Temperatures for:

Corn = 77 to 88 °F

Soybean = 65 to 84 °F

Wheat = 62 to 73 °F


Second Year Corn vs. Rotated Corn (Soybeans)

Corn Yield (Bu/A)

(2002 – 2005) (4 yr. Avg.)

Rotated Yield Advantage

Corn Hybrid Second Year Corn

Corn After Soybeans

Bu/A (%)

Non-Bt 177 196 +19 (11%)

Bt 179 198 +19 (11%)

Avg. 178 197 +19 (11%)

Yearly Range 161-193 177-219 +13-28 (7-15%)


Corn Ears: Good and Bad

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