Impacts of Changing Seeding Rates in Soybean• Weeds are the #1 IN soybean pest • Glyphosate resistance is a reality • Delayed canopy closure as row spacing increases 30 75 70

Impacts of Changing SeedingImpacts of Changing SeedingRates in SoybeanRates in Soybean

Shawn P. Conley Shawn P. ConleySoybean Extension SpecialistSoybean Extension Specialist

Purdue UniversityPurdue University

What is Driving ReducedSoybean Seeding Rates?

• Growing cost concerns:• Seed cost RR - 2007

• List price – $30.99 to 33.99• Farm gate – $23.50 to 26.50

• Non GMO• List price – ~$21.00• Farm gate – ~$15.00

• Seed treatment cost - 2007• Fungicide ~ $2.50 to $3.00• Insecticide + fungicide ~ $9.50

• What is it cheaper to do?• Plant more seeds or treat seed

Good Thing All Universities Agree!!

-----------Seeds or plants acre-1 -----------

119 to 179139 to 167111 to 13980%Kentucky-plants175 to 280139 to 174122 to 15790%Michigan-seeds200,000175,000140,00090%Missouri-seeds

---Wisconsin196,000160,000129,00090*90%Indiana-seeds196,000160,000129,00090*90%Ohio-seeds

90%

Germination -----Recommended Seeding Rates -----

125 to 140-

15”

200*125 to 140Iowa-seeds--Illinois

7.5”30”State

*Old versus new

What Else is Driving ReducedSoybean Seeding Rates?

• Farm equipment changes (farm size and technology)• Growers giving up the drill

• Uniformity in seed placement and emergence

• What is your average seeding rate by row spacing?

196,000

160,000

129,000

Purdue rec’s(90*90)

57%198,000≤ 10 in.

31%180,00011 ≥ x ≤ 20

12%155,000≥ 21 in.

% respondentsSeeding rateRow spacing

Conley and Santini, 2007

Common Questions Related to Variety Selection inReduced Soybean Seeding Rate Systems

• Variety selection – Is it important?

• Erect vs. bushy response to reducedplant populations or row spacing

• Real or marketing/grower perception?

• What about maturity group response?• Should I tweak my population based on

maturity group adaptiveness?

Soybean Variety Selection• Independent of farm size 28, 25, 29, and 18% of growers planted 1, 2, 3-

4, or ≥ 5 varieties of soybean in 2005.

• 55% of growers with 1000+ acres planted 4 or less varieties

2.32.22.22.12.3Seed Dealer

1.61.71.71.71.6Disease Resistance

1.81.81.51.61.5RR ® Ready Trait

1.21.41.41.41.5Yield Potential

3.23.13.03.12.9Grain Quality Traits

2.62.72.62.82.7Seed Company

2.42.52.42.52.3Seed Price

---------------------------------Rank (1-5)----------------------------------

1000+500 - 999250 – 499100 - 2490 - 99Grain Yield

---------------------------- Farm size (acres) ----------------------------

Conley and Santini, 2007

Maturity Group and Stem Phenotype Response toDecreased Soybean Populations

• Northern:• 2.8 and 3.6 M.G

• Southern:• 3.6 and 4.2

• Plant populations• 50,000 to 250,000

• Erect vs. bushy beans

• 10 site years; 4 varieties

• Drilled soybean (7.5”)

Impact of plant population on soybean yield

40.0

45.0

50.0

55.0

60.0

65.0

70.0

0 50,000 100,000 150,000 200,000

Stand Population

Yie

ld

ACRE NEPAC PPAC SEPAC

Does Planting Date Impact My Decision toReduce My Soybean Seeding Rate

Defining Planting Date Responses in Illinois*2001-2003 University of Illinois CMRA Project

-------------------- bushel/acre --------------------

46.648.948.945.3225

46.548.348.743.8175

46.547.648.341.9125

43.546.645.838.775

Late MayEarly MayLate AprilEarly April000/acre

Planting dateSeed rate†

*Soybean yield averaged over nine environments in Northern Illinois.†Seeding rates are expressed as viable seeds per acre.

Defining Planting Date Responses in Illinois*2001-2003 University of Illinois CMRA Project

-------------------- bushel/acre --------------------

33.734.635.432.9225

32.436.334.632.3175

32.835.333.729.3125

30.635.933.730.475

Early JuneLate MayEarly MayMid-April000/acre

Planting dateSeed rate†

*Soybean yield averaged over four environments in Southern Illinois.†Seeding rates are expressed as viable seeds per acre.

• “In Northern Illinois….Planting in early Aprilreduced yield by about 10 percent, and planting inlate May reduced yield by about 5 percent; theseresults suggest that planting “too early” tends toreduce yield more than planting late.”

• “It pays to wait to plant, but if planting is earlierthan ideal, it pays to add extra seed.”

Defining Planting Date Responses in Illinois2001-2003 University of Illinois CMRA Project

Emerson D. NafzigerUniversity of Illinois

• “In Northern Illinois….Optimum planting rates forplanting in the optimum window were about150,000 to 160,000 viable seeds per acre, but thisrose to above 200,000 per acre if planting wasearlier than the optimum time.”

• “Still it appears that planting rate should bebetween 150,000 to 175,000 viable seeds peracre in Southern Illinois.”

Defining Planting Date Responses in Illinois2001-2003 University of Illinois CMRA Project

Emerson D. NafzigerUniversity of Illinois

Does Row Spacing Impact My Decision toReduce My Soybean Seeding Rate

0

10

20

30

40

50

60

70

Bu/Ac

Seeding Rate (1000’s)250 220 190 160 130 100

167 159138

116 106

70

Harvest Pop

Yield

High Yield EnvironmentHigh Yield Environment

Should Yield Environment Affect Seeding RateShould Yield Environment Affect Seeding Rate

0

50

100

150

200

250

300

350

$

Seeding Rate (1000’s)

$ of Yield

Seed Cost ($)

Profit

250 220 190 160 130 100

Max

Economic Analysis for a High Yield Field

0

10

20

30

40

50

60

Bu/Ac

Seeding Rate (1000’s)250 220 190 160 130 100

225 204175

150108

78

Harvest Pop

Yield

Should Yield Environment Affect Seeding RateShould Yield Environment Affect Seeding Rate

Moderate Yield EnvironmentModerate Yield Environment

0

50

100

150

200

250

300

$

Seeding Rate (1000’s)

$ of Yield

Seed Cost ($)

Profit

250 220 190 160 130 100

Max

Economic Analysis for a Medium Yield Field

0

10

20

30

40

50

60

Bu/Ac

Seeding Rate (1000’s)250 220 190 160 130 100

197177

154

131

92 65

Harvest Pop

Yield

Should Yield Environment Affect Seeding RateShould Yield Environment Affect Seeding Rate

Low Yield EnvironmentLow Yield Environment

0

50

100

150

200

250

300

350

$

Seeding Rate (1000’s)

$ of Yield

Seed Cost ($)

Profit

250 220 190 160 130 100

Max245

Economic Analysis for a Low Yield Field

• Weed control implications• Weeds are the #1 IN soybean pest• Glyphosate resistance is a reality• Delayed canopy closure as row spacing increases

65707530404550152530357.5

5/16 to 5/255/6 to 5/15< 5/5----------May planting date ----------Row Spacing

Common Questions Related to Weed Management inReduced Soybean Seeding Rate Systems

Soybean Yield Loss Influenced by the Timing of

Weed Removal and Row Spacing

0

5

10

15

20

25

30

35

40

V1 V2 V3 V4 V5 V6 V7 R1 R2 R3

Timing of weed removal (Soybean growth stage)

Yie

ld L

os

s (

% w

ee

d f

ree

)

7.5"

15"

30"

Knezevic et al. 2003.

Weed Management in GR Soybean

• 26% of respondents indicated that they applied apreemergence herbicide to their soybean crop.

• 23% of growers indicated that they utilized a one passweed control program.

• The percentage of growers utilizing a one trip weedcontrol programs was 40% (99 or less), 34% (100 to249), 20% (250 to 499), 13% (500 to 999), and 11%(1000+).

• One pass program produced a 5.8% yield losscompared to those growers with 2+ passes.

Johnson et al. 2007

What is the Take Home Message

• Growers are slowly backing off seeding rates• Driven by seed cost and equipment changes

• Variety selection based on yield potential and defensive traits isimportant; canopy architecture is not important

• Planting date will affect seeding rate• Critical factor is getting a base population ≥ 100,000

• Row spacing and environment factors are related to maximizingleaf area

• Don’t forget about weed competition and glyphosate resistance• (Weed Scientists aren’t that bad after all)

Acknowledgements

• Nicole Fink – Purdue University• Emerson Nafziger – University of Illinois• Seth Naeve – University of Minnesota• Jim Beuerlein – The Ohio State University• Paul Carter - Pioneer Hi-Bred International• Kevin Cavanaugh – Beck’s Superior Hybrids

Friends DonFriends Don’’ttLet FriendsLet FriendsPlant Corn!Plant Corn!