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Master of Science in Agronomy Program – Plant Population Effects on Corn Yields and

Ear Characteristics to Evaluate Thinning in Research Yield Trial Plots

Kevin BetzApril 16th, 2010

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• Introduction/Background

• Project Creation

• Plant density review

• Objectives

• Material and Methods

• Results and Discussion

• Summary

Overview

Master of Science in Agronomy Program

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Background• Grain and Livestock Farm

– Mendota, IL

• Education– Associate of Science

• Southwestern Community College; 1998-2000

• Major: Agricultural Business

– Bachelor of Science• Iowa State University; 2001-

2003• Major: Agricultural Studies• Minor: Agronomy

– Masters of Agronomy Program• Fall 2005-Current

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Background• Monsanto- Williamsburg, IA

– 2003, Research Technician– 2004, Research Assistant

• Monsanto- Thomasboro, IL– 2008, ICB Coordinator

5

Project Creation

• Field research project during the 2008 growing season

• Plant density trial conducted

• Idea was to evaluate thinning of yield trial plots by looking at hybrid response to plant density

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Project Creation

• Why??– Corn plant densities continue to rise in

commercial agriculture– Private sector must evaluate new hybrids at

higher densities– General interest in how hybrids respond to

plant density– Monsanto’s commitment to double yield by

2030

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Project Creation

• World population of over 9 billion by 2040

• U.S planted 86.5 million acres of corn in 2009

• A 1.5% annual increase in corn grain yield is needed

• The last 30 yrs we have had a 1.3% annual increase

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Project Creation

• Plant densities are going to play a significant role in doubling grain yield by 2030

• Important to evaluate new hybrids at commercially recommended densities.

• Thinning of yield trial plots is a major job task involving many people and hours– Is there a chance it could be reduced?

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Plant Density Review

• Advancement in corn genetics has led to hybrids withstanding higher levels of stress

• Adoption of traits since the mid-90’s has given farmers additional measures to protect yield

• Research has shown that hybrids with Bt have increased yields – Singer et. al. showed 5-8% yield increase with Bt hybrids– Cox et. al. (2009) showed double and triple-stack hybrids yielded

2.7% more than their base genetics

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Plant Density Review

• Abundance of plant density data available • Data from recent years has shown that the

optimum plant density has increased– University of Minnesota recommends target planting rate of

33,000 seeds/acre– Purdue University recommends no less than 30,000 plants/acre

for a final stand– Iowa State University data in 2006 showed 36,000 seed/acre– Monsanto data shows 33,000-38,000 seeds/acre

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Corn crop densities for states in the Corn Belt

0

5000

10000

15000

20000

25000

30000

35000

IL IN IA MN NE OH WI

State

Pla

nts

pe

r a

cre

1991 1995 2000 2005 2009

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Plant Density Review

• Research has shown that yields have increased when plant densities are increased

• Continuing research will be vital to ensure farmers have knowledge of optimum planting densities

• Private sector must test new hybrids under higher densities to see performance

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185

190

195

200

205

210

215

220

23000 28000 33000 38000 43000

Corn

Yiel

d (bu

shels

per a

cre)

Plant Population (plants per acre)

Effect of plant density by year averaged across locations, row widths and germplasm (figure from Monsanto, 2010).

Source: Monsanto. 2010. Data Review-Corn Plant Density.Marcus Jones PH.D Technology Development Manager Corn Systems

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Ear Growth Characteristics

• Companies characterize hybrids by ear type– Fixed (determinate)– Flexed (indeterminate)

• Why does ear type matter?– If a hybrid can truly flex then it could compensate for variations

in plant density– Theory is as plant density is increased fixed-ear hybrids would

yield better, conversely as plant density decreases flexed-ear hybrids would yield better

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Ear Growth Characteristics• Also important in the Western Corn Belt where water is

limiting resource and plant densities are typically lower

• Very little scientific research comparing hybrid ear-type and their response to varying plant densities– Thomison and Jordan (1995) found that hybrid differences in ear

growth had a small effect on yield response to density– Cox (1997) reported that ear type did not contribute much to

hybrid variability for optimum plant density

• Interested in seeing if hybrid response to plant density varied by ear-type

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Yield Components

• Four components– Plants per acre– Ears per plant– Kernels per ear

• Kernels per row (KPR)• Kernel rows per ear (RPE)

– Kernel weight

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Kernel Rows per Ear (RPE)• Determined between V5-V8 growth stages

• Will always be even because of the splitting of the ovules to produce two rows

• Mostly determined by genetics but early season stress can have negative impact– Subedi and Ma (2005) found that nitrogen deficiency before V8

caused substantial decrease in RPE as well as kernels per row

• Increasing plant density could potentially affect RPE for flexed-ear hybrids while fixed-ear hybrids would in theory continue to produce the maximum number of RPE

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Kernels per Row (KPR)

• Varies much more due to environmental stresses• Maximum KPR is determined just prior to pollination

when ovule formation is complete• Upwards of 1,000 potential ovules per ear• Stresses leading up to V12 can reduce the KPR by

reducing the number of ovules formed• Stresses during and after silking can reduce the total

number of kernels per ear– Select ovules are sacrificed so that the plant can supply others

ovules

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Kernels per Row (KPR)

• Flexed-ear hybrids in theory could compensate depending on the stress level from V5 to just prior to silking

• Fixed-ear hybrids would not be able to respond to more favorable conditions

• If fixed-ear hybrids respond to higher plant densities then it shows that they are able to set enough kernels to maximize yields under favorable conditions

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Kernel Weight

• Estimates show that 85% of the final yield is correlated with the total number of kernels and the final 15% is determined by the final kernel weight

• Late-season stress caused by drought, insect, disease or loss of leaf area can severely reduce kernel weight

• Studies have shown that as plant density is increased kernel weight is decreased– Lamm and Trooein (2001)– Cox (1996)

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Monsanto testing footprint reaches hundreds of different environments

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Thinning

• The removal of plants and plant competition within each plot

• Done prior to V6 growth stage

• Time consuming and costly on such a large scale

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Thinning

• Research is very limited on effects of thinning – Hashemi et. al. showed that the greatest yield difference were

when plant competition occurred between V5 and anthesis– Early-season competition (V5) had little effect on final grain yield– Nafziger showed that as thinning was delayed the ability for

remaining plants to compensate decreased

• Within-row plant spacing and emergence could also affect final grain yield

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Objectives

• Determine a range of plant density variability that could be tolerated without affecting yield comparison's among hybrids

• Look at effects of plant density on both fixed-ear and flexed-ear hybrids

• Determine if thinning could be reduced

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Locations

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General Site Information

LocationSoil Common Name (Taxonomic

name), Planting

DateHarvest

Date Fertilizer rates lbs/acre Weed Control, Chemicals

N P K

Farmer City, ILIpava silt loam (fine, smectitic,

mesic Aquic Argiudolls) 5 May 12 October 236 92 120 Bicep II, atrazine, callisto, cultivation

Bloomington, IL Ipava silt loam (fine, smectitic,

mesic Aquic Argiudolls) 5 May 17 October 170 40 120 Lumax, atrazine, callisto, cultivation

Thomasboro, IL

Drummer silty clay (fine-silty,mixed,superactive,mesic, Typic Endoaquolls) 4 May 3 October 290 NA* NA*

Harness Xtra, atrazine, callisto, option, cultivation

Oxford, IN

Darroch silt loam (fine-loamy, mixed, superactive mesic aquic argiudolls) 6 May 8 October 147.5 52 120

Degree Xtra, laudis, aatrex, cultivation

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Planting Equipment

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Experimental Design

• Split plot with whole plots in a RCB with two replications

• Densities were main plots

• Hybrids were sub-plots

• Density whole plots were completely randomized within replicates at each location and within each plant density, hybrids were randomized

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Experimental Design

• Four locations• Four hybrids

– 113-115 RM, two fixed-ear, two flexed-ear

• Nine plant densities– 27,404-38,038 plants per acre

• Two replications• Seeding rate of 42,000 seeds/acre• Four 30-inch rows

– All four rows thinned to final stand

• Data collected only on middle two rows

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Farmer City plot design

27404 28631 29858 31085 33312 33539 35175 36402 38038

9 B B B B B B B B B B B B B B B B B B B B B B B B

Rep 2 8Rep2 7Rep2 6Rep1 5Rep1 4Rep1 3

2 B B B B B B B B B B B B B B B B B B B B B B B B

Range 1 B B B B B B B B B B B B B B B B B B B B B B B BCol 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

64-24 63-42 64-44

64-79 65-44 64-2464-24 65-44 63-4264-24

63-42 64-79 64-24 65-4463-42 65-44 64-79 64-2464-24 64-79

63-42 64-2464-79 65-4465-44 63-4264-24 64-79 65-44 63-42 63-42 64-24 65-44 64-79

65-44 64-7963-42 63-42 64-79 65-44 64-24 64-24 63-4265-44 64-2464-24 64-79

64-79 63-42 65-4465-44 63-4264-79 63-42 64-24 64-79

64-2464-2463-42

64-79 6424 64-7964-79 65-4465-44 63-42

64-79 63-42 65-4465-4464-79 63-42

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Hybrids

Hybrid Relative maturityDKC63-42-Med Flex 113DKC64-79- Flex 114DKC64-24- Fixed 114DKC65-44- Fixed 115

• Two fixed-ear, and two flexed-ear• All hybrids contained Yieldgard VT triple trait

combination

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Field Data

• Stand counts• Plant Height• Stalk lodging• Root lodging• Harvest Data

– Grain weight (lbs.)– Moisture– Test weight

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Lab Data• Six ears from center two rows collected

– Used to collect RPE, KPR and kernel weight

• Kernels per row– Measured from base to tip

• Kernel rows per ear– Measured from center of ear

• Kernel weight– 100 seeds counted and weighed

Photo courtesy of: Elmore, R, 2006. Iowa State University Extension

16 Kernel Rows 14 Kernel Rows

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2008 Weather

Sourcehttp://www.ncdc.noaa.gov/oa/climate/research/2008/oct/6month.html

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2008 Weather

Source: http://www.isws.illinois.edu/atmos/statecli/cuweather/index.htm

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Results• Traits analyzed

– Yield– Moisture– Test weight– Kernel rows per ear– Kernels per row– 100 kernel weight– Stalk lodging– Root lodging– Plant height

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Yield Results

218A218A217A217A220A217A208BC216AB207C+

0

50

100

150

200

250

2741

2

2855

5

2974

4

3098

4

3227

5

3361

9

3502

0

3648

0

3800

0

Plant Density (plants/acre)

Gra

in Y

ield

(bu

/acr

e)

† Means followed by same letter are not different

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Yield Results

221A217AB+ 212B212B

0

50

100

150

200

250

DKC63-42-Med Flex

DKC64-79-Flex

DKC64-24-Fixed

DKC65-44-Fixed

Hybrid-Ear Type

Grain

Yield

bu/ac

re

DKC63-42-Med Flex

DKC64-79-FlexDKC64-24-Fixed

DKC65-44-Fixed

† Means followed by same letter are not different

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Grain Moisture Results

25.8CD25.5D25.7D25.6D25.9BCD26.5A25.9BCD26.3ABC26.3AB+

2022242628303234

2741

228

555

2974

430

984

3227

533

619

3502

036

480

3800

0

Density (plants/acre)

Gra

in M

oist

ure

%

† Means followed by same letter are not different

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Grain Moisture Results

26.6B

24.7D25.5C

27.1A+

2021222324252627282930

DKC63-42-

Med Flex

DKC64-79-

Flex

DKC64-24-F

ixed

DKC65-44-F

ixed

Hybrid-Ear Type

Grai

n M

oist

ure

%

† Means followed by same letter are not different

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Test Weight Results58.8A

57.9C58.4B

57.5D+

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51

52

53

54

55

56

57

58

59

60

DKC63-42- Med F

lex

DKC64-79-Flex

DKC64-24-Fixed

DKC65-44-Fixed

Hybrid-Ear Type

Test

wei

ght (

lbs/

bush

el)

† Means followed by same letter are not different

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Kernel Rows per Ear

15.6C17.5A16.5B+ 17.5A

02468

101214161820

DKC63-4

2-Med

Flex

DKC64-7

9-Flex

DKC64-2

4-Fixe

d

DKC65-4

4-Fixe

d

Hybrid-Ear Type

Ker

nel

Ro

ws

per

Ear

† Means followed by same letter are not different

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Kernels per Row

29.6E

30.7D31.3CD

32.2BC32.1B32.8B32.8B

33.7A+ 34.0A

272829303132333435

2741

228

555

2974

430

984

3227

533

619

3502

036

480

3800

0

Plant Density (plants/acre)

Ker

nels

/Row

† Means followed by same letter are not different

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Kernels per Row

30.2C31.3B33.6A33.5A+

05

10152025303540

DKC63-42

-Med

Flex

DKC64-79

-Flex

DKC64-24

-Fixed

DKC65-44

-Fixed

Hybrid-Ear Type

Ker

nels

/Row

† Means followed by same letter are not different

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DKC64-79-FlexDensity: 27,412

DKC64-79-FlexDensity: 38,000

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DKC65-44-FixedDensity: 27,412

DKC65-44-FixedDensity: 38,000

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100 Kernel Weight

34.8A 34.7A

33.7B+33.3B

32.3C32.6CD

32.2C

31.2D31.7CD

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30

31

32

33

34

35

36

27412 28555 29744 30984 32275 33619 35020 36480 38000

Plant Density (plants/acre)

Kern

el W

eigh

t (gr

ams/

100K

)

† Means followed by same letter are not different

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100 Kernel Weight

Hybrid Grams/100K

DKC64-24-Fixed 33.5A

DKC65-44-Fixed 33.3A

DKC64-79-Flex 33.0A

DKC63-42-Med Flex 31.8B

† Means followed by same letter are not different

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Root Lodging

2.8A2.4AB

1.8ABC

1.1BCD1.0CD1.1BCD

0.3D0.4D0.7CD+

0.0

1.0

2.0

3.0

4.0

5.0

27412 28555 29744 30984 32275 33619 35020 36480 38000

Plant Density (plants/acre)

Roo

t lod

ging

%

† Means followed by same letter are not different

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Root LodgingHybrid Root Lodging Percent

DKC64-79-Flex 2.1A

DKC63-42-Med Flex 1.9A

DKC64-24-Fixed 0.85B

DKC65-44-Fixed 0.22B

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Conclusions

• No hybrid response to increasing density for:– Yield– Grain moisture– Test weight– Kernel row numbers– Kernels per ear– Kernel weight– Stalk lodging– Root lodging– Plant height

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Conclusions

• The number of kernel rows per ear was less affected by density then was the number of kernels per row and kernel weights

• Difficult to conclude that a reduction in thinning could be warranted based on one year of data

• Could be worthwhile to continue to investigate if thinning could be reduced– If the range of plant densities can be increased without causing

negative impact on yield comparisons

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Conclusions

• This study showed that the two lowest densities limited the hybrids ability to yield and should be considered on the low end of what should be used to evaluate new hybrid performance

• Fixed-ear hybrids are not being given an advantage based on this data set

• Increasing density does not seem to favor either a fixed-ear or flexed-ear hybrid

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Acknowledgements• Iowa State University

• Drs. Elmore, Moore and Loynachan

• Dr. Mowers

• All of my colleagues at Monsanto

• Wife and family

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Questions?