Corn After Corn: Agronomic and Farm Management Considerations

Bruce EricksonDepartment of Agricultural Economics

Certified Professional Agronomist

Learning Tuesday Session, February 20, 2007 2

Why More Corn Acres?

• Demand from Ethanol Production• Long-Term Yield Trend Favoring Corn• South American Soybean Production Influencing

Prices• Soybean Pest Concerns• Rotation Not Controlling Rootworms in E. Corn

Belt• Decrease in Price Ratio Soybeans/Corn

Learning Tuesday Session, February 20, 2007 3

0

20

40

60

80

100

120

140

160

180

1965 1970 1975 1980 1985 1990 1995 2000 2005

Yield, bu/A

U.S. Yield Trends

CORN

SOYBEANS

Learning Tuesday Session, February 20, 2007 4

South American Soybean Production Outpacing U.S.

Chicago Board of Trade

Learning Tuesday Session, February 20, 2007 5

Soybean Pest Concerns

• Sudden Death Syndrome• Soybean Cyst Nematode• Soybean Aphids• Asian Rust

In the past it was rare to treat for anything in-season for soybeans—Soybean Aphids have changed that paradigm

Soybean Aphids

Learning Tuesday Session, February 20, 2007 6

Corn Rootworm RiskCorn After Soybeans

Purdue Department of Entomology

Learning Tuesday Session, February 20, 2007 7

Returns Are Affected By

• Ratio of corn yield to soybean yield

• Ratio of corn price to soybean price

• Input cost differences

• Timeliness issues

• Ability to put the management pieces together to develop the system

Learning Tuesday Session, February 20, 2007 8

Shnitkey, Univ. of Illinois, Farm Economics Facts and Figures, 2006

Learning Tuesday Session, February 20, 2007 9

Ratio of Corn to Soybean Acres (2005)

Shnitkey, Univ. of Illinois, Farm Economics Facts and Figures, 2006

Learning Tuesday Session, February 20, 2007 10

Uni

vers

ity C

rop

Rot

atio

n R

esea

rch

Primary Author, Year Location Study Years Rotation vs. Cont Corn %

Crookston 1991 Lamberton & Waseca, MN 1981-1989 9

Edwards 1988 Crossville, AL 1981-1984 -24

Griffith 1988 Butlerville, IN 1980-1986 -7

Howard 1998 Grand Jct., TN 1986-1992 11

ISU, 2002 Nashua, IA 1979-1998 12

Katsvairo 2000 Aurora, NY 1993-1997 19

Lauer 1997 Lamberton and Waseca, MN, Arlington, WI 1981-1996 13

Lee 2004 Lexington, KY 1984-1997 9

Lund 1993 Arlington, WI 1989-1991 8

Meese 1991 Arlington, WI 1987-1989 16

Pedersen 2002 Arlington, WI 1995-1997 13

Pedersen 2003 Arlington, WI 1998-2001 15

Peterson 1989 Mead, NE 1983-1986 12

Porter 1997 Lamberton, MN 1985-1995 13

Porter 1997 Waseca, MN 1986-1995 10

Porter 1997 Arlington, WI 1987-1995 16

Riedell 1998 Brookings, SD 1994-1995 11

Singer 1998 Aurora, NY 1993-1994 5

Singer 2003 Pittstown, NJ 2000-2001 2

Univ. of IL Ext., 2002 IL 17 Site years 18

Varvel 2003 Shelton, NE 1993-2003 3

Varvel 2003 Mead, NE 1983-2003 3

Vyn 2004 Wanatah, IN 1997-2004 8

Vyn 2004 West Lafayette, IN 1975-2004 8

Walters 2004 Mead, NE 1999-2004 3

Wilhelm 2004 Mead, NE 1986-2001 23

Rot

atio

n C

orn

+9%

Learning Tuesday Session, February 20, 2007 11

Variable Costs of Corn After Corn

Learning Tuesday Session, February 20, 2007 12

Economics of Corn After Corn

• Higher Input Costs– Fertilizer, especially nitrogen– Tillage– Somewhat higher seed costs– Higher pest control cost (rootworm, etc.)

• Increased Timeliness Constraints at Planting

• Decreased Timeliness Constraints at Harvest

• Greater Machinery Costs

Learning Tuesday Session, February 20, 2007 13

Rotation Options

• Corn/Soybean

• Corn/Corn/Soybean

• Some Acres Corn/Soybean, Some Continuous Corn

• Many others

Learning Tuesday Session, February 20, 2007 14

Linear Programming Analysis

• If it costs more to grow continuous corn, what grain price advantage for corn, or how much more corn yield will it take for continuous corn to occupy more of your farm’s acres?

Learning Tuesday Session, February 20, 2007 15

Continuous Corn Model for Linear Programming

• 3000 acre farm• 2 full-time employees, 6 part-time employees• 3 large tractors, 2 small tractors• 42-ft disk and field cultivator, mini-moldboard plow• 24-row planter• 12-row corn head; 30-ft platform soybean head• 400,000 bushel on-farm grain storage• Purdue B-21 linear programming analysis has been

used for nearly 30 years on over 7000 farms to assist farm-level decisions; Also used in published research, master’s and doctoral dissertations

Learning Tuesday Session, February 20, 2007 16

Key Linear PC-LP Results

• Higher Machinery Costs

• Greater Constraints at Planting Time

• Relaxed Constraints at Harvest

• Continuous corn must yield substantially more, or soybean/corn price ratio must be small enough to justify

Learning Tuesday Session, February 20, 2007 17

What Corn/Soybean Price Ratio Justifies Continuous Corn?

0

500

1000

1500

2000

2500

3000

Acres Planted

2.23 2.32 2.42 2.52 2.64 2.76 2.90 3.05 3.22

Corn Prices

Rot.SoybeansRot. Corn

Cont. Corn

Cont. Corn Yield 215 bu/A 2.5 2.2 1.9

Robertson, 2006Soybean/Corn Price Ratio

Learning Tuesday Session, February 20, 2007 18

Agronomics for Corn on Corn

• Choose Best Fields• Increase N fertilizer• Plan for Rougher, Cooler Seedbeds

– Planting rates– Tillage– Plant after corn following soybean fields

• Increased threat of leaf disease– Hybrid selection– Fungicide

• Different insect threat– Rootworms primary threat—genetic and chemical options– Little difference in corn borers or seed-attacking insects

Learning Tuesday Session, February 20, 2007 19

Rotation Yield Difference by Yield Level (4-year study, U of MN)

Yield LevelBu/A

Yield Difference Bu/A

% Difference

110 32 29

120 17 14

140 24 17

155 25 16

165 12 7

180 5 3

200 5 2.5

Learning Tuesday Session, February 20, 2007 20

Corn Yield Response to Nitrogen Fertilizer

40

60

80

100

120

140

160

180

0 20 40 60 80 100 120 140 160 180 200 220 240

Rate of Nitrogen (lbs./acre)

Yie

ld (

bu

./a

cre

)

Corn After Corn Yield Response

Linear (N/Corn Price Ratio = .085)

Linear (N/Corn Price Ratio = .2)

EO

NR

EO

NR

Determining the Economically Optimum Nitrogen Rate

Optimum N occurs where marginal value of adding another lb. of N just equals the marginal cost of adding another lb. of N

Learning Tuesday Session, February 20, 2007 21

Learning Tuesday Session, February 20, 2007 22

Response to Tillage and Rotation1975-2006, West Lafayette

Corn/

Soy

Corn/

Corn

Gain for Rotation

Moldboard Plow

180 172 4%

Chisel Plow 180 168 7%

No-Till 175 150 18%

Vyn, 2006

Learning Tuesday Session, February 20, 2007 23

Increased Threat of Leaf Disease

• Anthracnose

• Eyespot

• Gray leaf spot

• Northern Corn Leaf Blight

Learning Tuesday Session, February 20, 2007 24

Rootworms Primary Insect Threat

• Western Rootworm Variant has changed rotation dynamics

• Genetic options for rootworms are excellent option

• Seed treatments for rootworms only effective with light pressure

• Threat of corn borers and seed-attacking insects not drastically different

Learning Tuesday Session, February 20, 2007 25

Corn on Corn Hybrid Selection

• Emergence, seed quality

• Early Growth

• High Residue Suitability

• Leaf and Stalk Disease Ratings

• Standability, resistance to stalk lodging and root lodging

• Insect Resistance ratings, and Insect Traits

• Herbicide Resistance traits, depending on weed management program

Learning Tuesday Session, February 20, 2007 26

Effect of Post Spray Timing on Weed Control and Yield (Michigan State University)

Weed size at application

Weed Control%

Corn Yield LossFrom Early Season Weed

Competition, %

2” 73 0

4” 83 3

6” 90 6

9” 93 14

12” 95 22

Learning Tuesday Session, February 20, 2007 27

Is There an Advantage for Long-Term Continuous Corn?

• Many successful continuous corn growers have developed a management scheme of interrelated practices

• Some say it is difficult to test systems approaches using traditional agronomic testing principles

Learning Tuesday Session, February 20, 2007 28

Continuous Corn/High Yields

• Herman Warsaw, Illinois – 1970s, >300 bu/A

• Francis Childs, Iowa– 1990s, >400 bu/A

• Mark Dempsey, Illinois– 2004 Illinois NCGA Champ,

320 bu/A

• 2005 and 2006 NCGA results

Learning Tuesday Session, February 20, 2007 29

Perceived Yield Differences

100

110

120

130

140

150

160

170

180

190

200

0 1 2 3 4 5 6 7 8 9 10

Years After Last Soybean Crop

bu

/A

Corn After Soybeans

Cont. Corn/Research

Cont. Corn/Farmers

Learning Tuesday Session, February 20, 2007 30

Long-Term Continuous Corn

• Increases in Organic Matter

• Increases in Available Nitrogen

• Improvements in Soil Quality

• Dobermann, Nebraska:

– Corn/soybean systems exploit soil C and N

– Continuous corn systems have the potential to build C and N

Learning Tuesday Session, February 20, 2007 31

Farmer Experiences From Long-Term Continuous Corn

• Very High Rates of N, P, and K

• High Planting Rates

• Attention to Hybrid Selection (Disease & Insect)

• Good Field Drainage

• Fall-Applied Nitrogen

• Intensive Tillage

• Many of the management practices for continuous corn are the same as they are for corn following soybeans

Learning Tuesday Session, February 20, 2007 32

Take-Home Messages

• Input costs and ratio of corn price to soybean price and yields key determinants of decision

• Successfully growing continuous corn may require:– More intensive tillage– Higher rates of fertilizer– Careful attention to plant genetics– Ability to manage a system as much as individual

components

Top Farmer Crop WorkshopJuly 22-25, 2007

West Lafayette

Bruce EricksonDepartment of Agricultural Economics

Purdue University (765)494-9557

berickso@purdue.eduberickso@purdue.eduhttp://www.purdue.edu/ssmc/http://www.purdue.edu/ssmc/

http://www.agecon.purdue.edu/topfarmer/http://www.agecon.purdue.edu/topfarmer/