Row Spacing & Seeding Rates for Corn

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Thoughts on Row Spacing & Plant Population R.L. (Bob) Nielsen Purdue University Agronomy Email: [email protected] KingCorn: www.kingcorn.org Chat ‘n Chew Café Café: www.kingcorn.org/cafe www.kingcorn.org/cafe v20101129

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Image source: Library of Congress

It’s all about capturing sunlight!

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Building a crop canopy  Every

agronomic decision you make potentially influences crop canopy development and the capacity to intercept sunlight. Hybrid Seeding rate Row width Irrigation

Soil fertility Weed control Planting date

Foliar fungicide

 Not

to mention the influences of weather, soils, and pests during canopy developmt.

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Row Spacing & Seeding Rates for Corn

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Bottom line on seeding rates…  Current

data suggest that many growers should be targeting economic FINAL stands no less than ~ 30,000 ppa; equal to a seeding rate of ~ 33,000 spa.  Exceptions being…  Lower yielding environments (e.g., 130 bpa or less) where growers should target final populations between ~ 24 to 30,000 ppa.  More northern areas where final stands may need to be 33,000 ppa or greater. v20101129

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Seeding Rates

Balancing act for corn…  More

plants per unit area equals more ears per unit area. (that’s good)  But, ear size per plant decreases with increasing plant density. (that’s not good)  The optimum final stand is that which best balances the decrease in ear size per plant with the gain in ears per unit area.  Furthermore, stalk health & integrity at higher populations sometimes falters. v20101129

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Image: http://ascannerdorky.files.wordpress.com/2007/07/balancing-act-001.jpg

Harvest populations - Illinois 30,000 25,000

29,650 21,900

y = 370.81x - 715593

20,000 15,000 10,000 5,000

Average harvest populations reported by Illinois corn growers have been steadily increasing by about 370 plts/ac/yr over the past 20 years.

0 1985

1990

1995

2000

2005

2010

2015

Source: USDA-NASS Crop Production Reports

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Harvest populations - Indiana 30,000 28,350 25,000

21,500

y = 309.66x - 594224

20,000 15,000 10,000 5,000

Average harvest populations reported by Indiana corn growers have been steadily increasing by about 310 plts/ac/yr over the past 20 years.

0 1985

1990

1995

2000

2005

2010

2015

Source: USDA-NASS Crop Production Reports

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Harvest populations - Illinois 100 90

Since 2007, a decrease in the middle populations and an increase in higher populations.

< 25,000

% of surveyed acres

25 - 30,000

80

> 30,000

70 60

56.7

50 40 32.1

30 20

11.2

10 0 1999

2001

2003

2005

2007

2009

2011

Source: USDA-NASS Crop Production Reports

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Harvest populations - Indiana 100 90

Since 2005, a decrease in the lowest populations and an increase in higher populations.

< 25,000

% of surveyed acres

25 - 30,000

80

> 30,000

70 60 50 40.5

40 30 20

19.1

10 0 1999

2001

2003

2005

2007

2009

2011

Source: USDA-NASS Crop Production Reports

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Grain Yield vs Final Stand 2007-2009 NCGA Winners

450 400

Grain yield

350 300 250 200 150

Very little relationship between grain yield and harvest plant population among the top winners.

100 50 0 25000

30000

35000

40000

45000

50000

55000

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Identifying optimum seeding rates  Seeding

rates represent a quantitative input, so ought to develop a yield response curve to estimate optimum rate.  Similar to how we evaluate N rates.

 Simply

comparing one rate vs. another may answer which is superior, but does not offer best estimate of optimum rate.

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My rate vs. your rate 8 Combinations of High vs. Low populations High 33k to 42k Low 28k to 35k 33 replicated strip trials (18 counties)

12 10 High pop yld - Low pop yld

8

Avg yield difference = - 0.2 bpa

6 4 2 0 -2 -4 -6 -8 -10

What do you learn from this effort?

Identities of the researchers have been removed to protect the guilty.

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Yield response to seeding rates  Is

not feasible to evaluate yield response to every possible seeding rate alternative.  So…….we evaluate yield response to four to six seeding rates that represent the range of possible seeding rates and then develop a yield response curve.  E.g., 29k, 34k, 39k, and 44k seeding rates.

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Yield response to seeding rates… rates…  Lower

and higher than optimum seeding rates included to capture full range of yield Rate higher than optimum response.

Rate lower than optimum

Est. optimum rate based on yield response curve

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Choice of response curves  To

describe yield response to plant density, there are alternative “shapes” of response curves to choose from.  Statistically, one or two or all of them may offer good “fits” to the data set.  Is a certain amount of responsibility on the researcher’s part to choose the model that visually reflects the yield response to the actual data.

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Row Spacing & Seeding Rates for Corn

200

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Simple linear

60

40

20

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0

0 15

20

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30

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Simple quadratic

60

40

40

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45

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30

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Common choices 200

200

180

180

160

160

140

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120

120

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Linear plateau

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Quadratic plateau

60

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Yield response example 200 180 160 140 120 100 80 60 40 20 0

R2 = 0.9467

•Quadratic response model; •Easy to create w/ Excel™ Excel™ •Offers good "fit" to the data

0

10

20

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Yield response example 200 180 160 140 120 100 80 60 40 20 0

•QuadraticQuadratic-plateau response model; •Requires more robust stats program; •Also offers good "fit" to the data

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Why does this matter? 

Choice of model can influence estimation of optimum plant population. 200

200

180

180

160

R2 = 0.9467

160

140

140

120

120

100

100

Quadratic model Optimum density ~ 39k

80 60 40

Quadratic plateau model Optimum density ~ 32k

80 60 40

20

20

0

0 0

10

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50

60

0

10

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More “curve balls” 

Percent of max. yield



Sometimes, you have no business trying to fit a yield response curve to the data. In other words, sometimes there is no yield response. 120% 100% 80% 60% 40% 20% 0% 20000

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25000

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30000

35000

Harvest population

40000

45000

25

An example… 10 locations, 2006*

 Recent

public data suggested an agronomic yield plateau occurred close to 36,000 seeding rate.  Supporting data points not shown.

* Identities of the researchers have been removed to protect the guilty.

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Follow-up to that data… 105 32 sites (2006(2006-2008)

Percent yield

100 95

Suggested optimum plant population ranging from 36k to 38k plts/ac, plts/ac, though confusing because previous response curve was for SEEDING rate.

90 85 80 75 15000

20000

25000

30000

35000

40000

45000

50000

Plant population (ppa)

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Data behind the curve… 105

32 sites (2006(2006-2008) 100 Percent yield

2

R = 0.0602

95 90 85 80

If these were your data, would you stand behind a quadratic model or any model?

75 15000

20000

25000

30000

35000

40000

45000

50000

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Yield response by yield level 36k

* Steve Paszkiewicz and Steve Butzen. 2007. Corn Hybrid Response to Plant Population. Crop Insights. Vol. 17. No. 16. Pioneer Hi-Bred Int’l.

36k

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35k

26k

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Whoa….let’s take another look  Those

data were analyzed by fitting quadratic curves to the yield response data.  What if a quadraticplateau model were used instead?

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Yield response by yield level 250 34k

200 32k

150 31k

100 Est’ Est’s of optimum population based on a QP model were 2k to 4k lower than those based on quadratic model.

130-160

50

160-190 >190

0 15

20

Data courtesy of Steve Paszkiewicz, Pioneer Hi-Bred (2007)

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30

35

40

45

Harvest population © 2011, Purdue University

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Source: Monsanto Technology Development. 2009 National Research Summary, “Evaluation of Corn Plant Density & Row Spacing”

Monsanto summary…

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Average of two row widths (20- & 30inch) and 21 hybrids across 60 trials

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Estimated optimum seeding rates for 113 RM hybrids grown in 3 yield environments.

Source: Monsanto Technology Development. 2009 National Research Summary, “Evaluation of Corn Plant Density & Row Spacing”

Seeding rates & yield levels

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Recent university data…  Iowa:

Suggests optimum final stands level out around 30,000 ppa.  Southern IL: Suggests optimum final stands closer to 24,000 ppa (more challenging soils).  Northern IL: Suggests optimum final stands near 35,000 ppa.  Central/southern MI: Suggests optimum final stands near 36,000 ppa. v20101129

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2001 - 2004 Large plot trials… Percent of max. yield

120% 100% 80% 60% 40% 20% 7 trials in WC, NE, and SE Indiana

0% 20000

25000

30000

35000

40000

45000

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2008 - 2010 Seeding Rate Trials  On-farm,

replicated trials to evaluate corn yield response to plant populations.  Farmer cooperators using their own farm equipment to plant and harvest.

 Contact

your local Extension educator or Certified Crop Adviser if you would like to participate in 2011.

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2008 - 2010 OFR trials… Percent of max. yield

120% 100% 80% 60% 40%

•Note similar response to older data with older hybrids

20% 12 trials, 11 counties

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Seeding rate decisions…  Are

influenced by actual yield response to plant population and the cost of seed.  Agronomic optimum seeding rates  Maximum yield regardless of cost.  Economic optimum seeding rates  Maximum $ return to seed inputs.

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Economic optimum population $590

Percent yield

100%

$580 $570

80%

$560

28 ~ 31,000 ppa ~ 33,000 spa

60%

$550 $540

40%

$530

•Seed cost: $250/80k unit •Grain price: $3.50/bu

20%

•Assumed yield: 200 bpa

$520

Pct Yld $ Return

$510

0% 15,000

Grain income - seed cost ($/ac)

$600

120%

$500 20,000

25,000

30,000

35,000

40,000

45,000

Final stand (ppa) RLN calculations based on data courtesy of Steve Paszkiewicz, Pioneer Hi-Bred (2007)

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Today’s elite hybrids?  Some

claim that today’s elite multiple biotech trait hybrids respond better to higher seeding rates than today’s elite non-biotech or simply RR hybrids.  However, there is little, if any, independent data to support the claim.  Today’s hybrids are simply more stress tolerant across the board than those of 20 years ago.

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Bt vs. non-Bt response, WI 

“It was concluded that Bt corn hybrids require higher plant populations for maximizing yield potential…”  42.3k vs. 40k plants per acre, but economically equal at 34k

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Bt vs. near isoline hybrids  Non-Bt

vs. Bt-RW or Bt-RW-ECB  Six site-yrs for corn / soy Two site-yrs for corn / corn  Yield responses to plant density equal  Economic maximum plant density across all hybrids ranged from 32k in IL to 37k in IA.

Data source: Coulter et al. (2010) v20101129

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Seeding rate decisions…  

Are not influenced very much by hybrid. Today’s hybrids in general have much better population tolerance than their predecessors.  Improved ability to maintain ear size at higher plant densities.  Less tendency to remobilize stored stalk carbohydrate reserves during stressful grain fill; thus less tendency for stalk lodging at higher plant densities.

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Image: http://ascannerdorky.files.wordpress.com/2007/07/balancing-act-001.jpg

Stalk health concern…  Remains

an issue for hybrids with moderate or worse stalk strength or stalk rot resistance.  Such hybrids should be planted at more moderate seeding rates to minimize the risk of severe stalk lodging prior to harvest.

Image source: http://www.sil.si.edu/imagegalaxy/imageGalaxy_SearchResult.cfm

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Bottom line w/ corn…  Current

data suggest that many growers should be targeting economic FINAL stands no less than ~ 30,000 ppa; equal to a seeding rate of ~ 33,000 spa.  Exceptions being…  Lower yielding environments (e.g., 130 bpa or less) where growers should target final populations between ~ 24 to 30,000 ppa.  More northern areas where final stands may need to be 33,000 ppa or greater. Image source: http://www.webwhispers.org/newspics/apr05/target.jpg

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Well, you might ask…  What

about “fixed” and “flex” ear hybrids?

 Surely their optimum plant populations differ?

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Good question…  Hybrids

are thought to differ for their ear size response to plant densities.  Commonly used terminology includes “flex”, “semi-flex”, or “fixed” ears.  “Flex” hybrids are thought to change ear size (kernel number) more dramatically in response to low or high plant density than that of “fixed” hybrids.

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Ear flex: Not well documented  Interestingly,

there is very little scientific literature that documents hybrid ear size response to plant density.  What little there is suggests that “fixed” and “flex” hybrids share common plant densities for achieving optimum grain yields.  Occasionally, I evaluate such hybrids in plant density demos at our crop diagnostic training center facility.

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2005 Comparisons…  Two

hybrids rated by a seed company as strongly “fixed” or “flex” were planted at 15, 30, 40, & 50k seeds per acre.  Random ears were sampled from each plot.  Numbers of kernel rows & kernels per row were counted for each individual ear.  Total kernels per ear were calculated and expressed as a percent of mean kernel number for 30k seeding rate.

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2005 Comparisons…



“Flex” hybrid indeed flexed at both low and high plant densities.

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

“Fixed” hybrid flexed more than “flex” hybrid???

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2006: Different pair of hybrids •More “flex” at low pops

Kernel no. per ear relative to 35k rate

180% 155%

160% 140%

•Less “flex” at high pops

140% 133%

120%

15k 25k 35k 45k 55k

111% 100%

100%

100% 84%

81%

77%

80% 64%

60% 40% 20% 0% Flex

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2008: Yet another pair of hybrids Kernel no. per ear relative to 35k rate

160%

Strongest company ratings for each category 145%

140%

•More “flex” at low and high pops

129% 121%

120%

110%

100%

100%

80%

15k 25k 35k 45k 55.8k

100%

79%

74% 67% 61%

60% 40% 20% 0% Flex

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Bottom line…  Essentially,

all hybrids flex ear size in response to changes in plant density.  Some flex more than others, but apparently not as consistently as some seed companies claim they do. v20101129

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Bottom line on seeding rates…  Current

data suggest that many growers should be targeting economic FINAL stands no less than ~ 30,000 ppa; equal to a seeding rate of ~ 33,000 spa.  Exceptions being…  Lower yielding environments (e.g., 130 bpa or less) where growers should target final populations between ~ 24 to 30,000 ppa.  More northern areas where final stands may need to be 33,000 ppa or greater. v20101129

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My opinion on row spacing…  Traditional

30-inch rows are not a primary limiting factor for corn grain yield today in the heart of the Corn Belt.

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The move to 30-inch rows…  Was

accompanied by a good consensus by public researchers throughout the Corn Belt that 30-inch rows would yield 6 to 7 percent better than 36- or 38-inch rows.  But, what about a move from 30-inch rows to narrower rows today?  Has garnered farm press attention for years.

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Some folks say…  “I’m

gonna switch to 20-inch rows because I hear the “big boys” are doing it and are harvesting 20 to 40 more bu/ac!”  “I’ve heard that narrow rows don’t work until you push populations to 45,000.”  “There’s been a rapid adoption of narrower rows in recent years.”

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Corn row spacing - Illinois % of reporting farmers

100%

95%

80%

60%

40%

< 30 inches 30 inches 36 inches or >

Overwhelming majority of growers still reporting use of 30-inch rows.

20%

0% 2000

2002

2004

2006

2008

2010

Source: USDAUSDA-NASS Crop Production Reports

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Corn row spacing - Indiana % of reporting farmers

100% 92%

80%

60%

40%

< 30 inches 30 inches 36 inches or >

Overwhelming majority of growers still reporting use of 30-inch rows.

20%

0% 2000

2002

2004

2006

2008

2010

Source: USDAUSDA-NASS Crop Production Reports

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Row spacing decisions are… are…  Influenced

by machinery issues:

 Equipment tire size  Post-planting operations  Planters & seed meters  Combine headers  Row irrigation  Compatibility with other crops

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Row spacing decisions…  Are

also influenced by the crop’s yield response to narrower rows…  Primarily related to plant-to-plant competition for available water, nutrients, and light.  If more than enough water, nutrients, & light; then NOT likely to see a significant response to narrower rows.

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Image source: http://www.nebkan.com/PrecisionAg.html

Response to row spacing…  Is

also related to whether the crop canopy is “capturing” at least 95% of the available sunlight during flowering or beyond. beyond  Barbieri et al. (2000), Maddoni et al. (2006)

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Light capture in wide vs narrow rows Up to ~ 95% light capture, narrow rows usually capture more light light than wider rows. Maddonni et al., 2006

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fPAR = Fraction of Photosynthetically © 2011, Purdue University Active Radiation intercepted by crop canopy

68

Yield response vs. light capture 

Possible ½ to ¾ percent yield increase for each percentage point increase in sunlight capture up to about 95% capture.

Yield increase to narrower rows relative to percent sunlight capture in wide rows. (Andrade et al., 2002)

 Andrade et al. (2002)

RI = Radiation interception v20101129

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Consequently…  Narrow

rows may be most beneficial where canopy development & yield are challenged by marginal soils or climates.     

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Northern climates (cooler, less growth). Nutrient deficient soils (esp. nitrogen). Sandy, non-irrigated, often droughty soils. Shorter-season hybrids. Smaller, shorter, less leafy hybrids.

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Use your eyes…  Estimate

% light capture by estimating % shade beneath the crop canopy shortly after noon on a sunny day in early July.  If less than ~ 95% shade, then likely not at maximum yield potential.

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Most public research…  Indicates

that yield response to row spacing narrower than 30 inches is generally positive, but very inconsistent.  Averaging 1.5 to 2.5% advantage.  Most have found that optimum seeding rates are similar for different row widths.

Image source: http://www.answers.com/topic/grain-belt

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Reported Responses to Narrow Rows (15- or 20-inch) 1984-95 10%

MI

5%

MN

Average response = + 1.5%

Ontario

PA

Ontario IA

IN

IL

0% IL IL

-5%

TN

OH

-10%

% Difference to narrow rows Source: Paszkiewicz, Paszkiewicz, 1996

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Reported Responses to Narrow Rows (15- or 20-inch) Since 1996 15%

Average response = + 2.6%

10%

MN

5%

MN

MI MI

NE WI

0% IA

-5% Argentina

-10%

WI

-15% % Difference to narrow rows Sources: scientific literature

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Relative yield advantage to twins

Purdue twin row data 2009 100%

•Westcentral Indiana 2009 •Four seeding rates (28 – 43 spa) [no interaction among seeding rates] •Average yield for trial = 232 bpa

90% 80% 70% 60% 50% 40% 30% 20% 10%

0.5%

0.8%

1.2%

111-day

107-day

0% 112-day

Hybrid (maturity)

Source: T. Vyn, Vyn, Purdue Agronomy

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Relative yield advantage to twins

Purdue twin row data 2010 100%

•Westcentral Indiana 2010 •Four seeding rates (28 – 43 spa) •Average yield for trial = 192 bpa

80% 60% 40% 20%

0.6%

0.0%

1.0%

33k

38k

43k

0% -1.0% -20% 28k

Source: T. Vyn, Vyn, Purdue Agronomy

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Purdue OFR data, 2010 30-inch

250

Twins Not significant

Not significant

Grain yield

200

Significant ~ 2.9% diff.

150 100 50 0 Trial 1

Trial 2

Trial 3

Source: Smith, Fryman, Fryman, & Nielsen

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Data from industry sources…  Varies,

but tends to show similar relatively low percent yield responses for narrow rows; including twin-row configurations.

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Grain Yield Response to 22.5-inch Rows (Pioneer Hi-Bred Int'l, 1991-95) 10%

Statistically significant response to 22.522.5-inch rows at 5 of 16 trials. Across all 16 trials, average response to 22.522.5-inch rows = + 4.1%

9% 8% 7% 6% 5% 4% 3% 2% 1% 0% SD MN SD MN

IA MN IA ND SD MN MN

IA

IA

IA

IA

SD

Source: Paszkiewicz, Paszkiewicz, 1996

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Significant row spacing effect only in eastern Iowa (+ 5.5%)

Averaged over 2 years, 10 locations, 21 hybrids, 5 seeding rates, & 3 replicates per ecozone

Source: Monsanto Technology Development. 2009 National Research Summary, “Evaluation of Corn Plant Density & Row Spacing”

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4 bu max ~ 1.9%

Averaged over 80 sites, 40 hybrids, 10 locations, & 3 replicates per year

Source: Monsanto Technology Development. 2009 National Research Summary, “Evaluation of Corn Plant Density & Row Spacing”

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Monsanto Twin Row Data 2009 Relative yield advantage to twins

100% 90% 80%

Twenty locations across 10 states

70%

Twins vs. 3030-inch rows

60%

Four seeding rates (28 to 43k) [slight interaction among seeding rates]

50% 40% 30% 20% 10%

0.60%

1.90%

2%

< 190 bpa

190 - 235 bpa Yield levels

> 235 bpa

0%

Source: http://www.twinhttp://www.twin-row.com/sites/default/files/monsanto_twinrowreport.pdf

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2009 DEKALB Twin Row Trials (Illinois)

250

~ 4.2%

~ 2.3%

~ 2.4%

200 150 30-inch Twins

Average advantage to twins ~ 2.3% 100

50 0 28000

33000

38000

43000

Plants per acre Source: http://www.twinhttp://www.twin-row.com/sites/default/files/agrigold_twinrow.pdf

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2009 DEKALB Twin Row Trials (Illinois) 45% Avg. response to twin rows = + 3.1%

Percent of trials

40% Range of yield responses

35%

-10% to -6% -5% to -1% 1% to 5% 6% to 10% 11% to 15% 16% to 20%

30% 25% 20% 15% 10% 5% 0%

Source: http://www.twinhttp://www.twin-row.com/sites/default/files/DeKalb2009_yieldresults.pdf

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Other reports of higher yields…  Are

more difficult to assess because details of the comparisons are not clear.

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Other reports of higher yields…  Not

uncommon for on-farm trials to compare 30-inch rows planted at one seeding rate with a narrow row spacing at a higher seeding rate.  30-inch rows @ 28k  20-inch rows @ 35k

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Other reports of higher yields…  In

some cases, I suspect that documented yield increases to narrow rows may be related to slower seed metering and more uniform stand establishment when planting at aggressively high seeding rates and fast planting speeds.

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Bottom line on row spacing…  Traditional

30-inch rows are not a primary limiting factor for corn grain yield today in the heart of the Corn Belt.  Profitability depends on costs to change, acreage, potential yield, & grain price.

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