Researchers: Continuous Corn Yield Penalty Persists Seven Years

As escalating corn prices have encouraged many farmers to switch to growing corn continuously, they wonder why they have been seeing unusually high yield reductions over the past several years. The University of Illinois conducted a six-year study that identified three key factors affecting yield in continuous corn (CC) systems.

“Prior to this study, the most common management recommendations for continuous corn production were to apply an additional 45 pounds of nitrogen per acre and reserve your best crop land for it,” said U of I soil scientist and lead author Laura Gentry. “Very little was known about the agents or mechanisms causing reduced yields in continuous corn systems.”

Although corn can be cropped continuously, it is widely accepted that there is a yield reduction compared to corn rotated with soybean (CS). This difference is referred to as the continuous corn yield penalty (CCYP), which is generally in the range of 20 to 30 bushels per acre. The 2012 growing season marked the third consecutive year of unusually high CCYP values in the U.S. Midwest, often with corn yields that were 30 to 50 bushels per acre less than corn following soybean.

The researchers conducted the experiment from 2005 to 2010 in east-central Illinois, beginning with corn produced in a third-year CC system or a CS rotation, at six N fertilizer rates. The study investigated:

  • How the yield penalty changed with time in CC.
  • Under what conditions does increasing the nitrogen (N) fertilizer rate reduce the penalty?
  • What causes the penalty?

Each year, they determined an “agronomically optimum N rate” and corresponding yield value for each rotation (CC and CS). On average, corn yield at the agronomically optimum N rate for CC was 167 bushels, compared to 192 bushels per acre for CS – a CCYP of 25 bushels per acre. CCYP values ranged yearly from 9 to 42 bushels per acre.

Matias Ruffo, a co-author of the paper and Worldwide Agronomy Manager at The Mosaic Co., said, “To explore the causes of the CCYP, we tested a number of different weather- and yield-related measurements for their relationships with the CCYP. We found that with just three predictors, we could estimate the CCYP with almost 100% accuracy.” The predictors were: 1) unfertilized CC yield, 2) years in CC, and 3) the difference between CC and CS delta yields.

The researchers found that the best predictor of the CCYP was unfertilized CC yield. In years when unfertilized CC yields were relatively high, the yield penalty was low, and vice versa. Unfertilized CC yield is an indicator of how much N the soil is supplying to the corn crop, either from residual fertilizer N or from decomposition of previous crop residues and other organic matter (N mineralization).

The second predictor of the CCYP, years in CC, was also strongly correlated with the CCYP. CCYP got worse with each additional year in the CC system through the seventh year, when the study was terminated.

This conclusion is at odds with the claims of many Corn Belt farmers who argue that corn yields in CC eventually attain the same level as CS rotations. On average, the CCYP in this study increased by 186% from third-year CC to fifth-year CC and 268% from third-year CC to seventh-year CC.

“Yield reductions resulting from additional years of continuous corn production mirror the effects of residue accumulation when corn is cropped continuously,” said U of I crop physiologist Fred Below, another co-author. “It is well documented that corn residues introduce a host of physical, chemical, and biological effects that negatively influence corn yields.”

Effects of accumulated corn residues include reduced soil temperature, increased soil moisture, reduced N fertilizer availability, and production of autotoxic chemicals, all of which can negatively affect growth and future corn crop development.

The final predictor of the CCYP, difference in CC and CS delta yields (the difference between the yield where no N was applied and the maximum yield under non-N limiting conditions), is probably a function of weather conditions, particularly during critical growth periods such as ovule determination and grain fill. Drought and heat can disproportionately reduce yields of the CC system relative to the CS system. This principle was demonstrated during the 2012 drought, when farmers reported yield reductions as large as 50 bushels per acre for CC systems compared to CS.

Based on this study, the authors concluded that the CCYP persists for at least seven years. However, during very favorable growing seasons, increased N rates can overcome the CCYP. Unfortunately, higher N rates do not eliminate the CCYP during average or poor growing seasons. This study concluded that the primary causes of the CCYP are: N availability, corn stover accumulation, and unfavorable weather.

Leave a Reply

Crop Inputs Stories
Crop InputsPlatform Specialty Products To Acquire Arysta LifeScience
October 20, 2014
Once the acquisition is complete, Platform Specialty Products will combine Arysta LifeScience with previously acquired companies Agriphar and Chemtura Crop Solutions. Read More
MicronutrientsMicronutrients Going Macro
September 9, 2014
Between 2014’s fantastic growing conditions and a heightened awareness on plant nutrition, the major players in micronutrients are gearing up for another big year. Read More
FertilizerFall Fertility 2014: Forecasting Fertilizer Use
September 7, 2014
Great crops this year have tapped the soil, and fall work is definitely called for, but how challenging will that get? Read More
FungicidesSudden Death Syndrome, Brown Stem Rot Reported In Indiana Soybeans
September 3, 2014
Farmers and retailers should be watching for symptoms of these two diseases over the next few weeks as they are best managed through preventative methods. Read More
Top 100 Articles
Milan Kucerak, president/CEO, West Central
CropLife 100West Central Cooperative And Its New President Are A Match Made In Deviation
June 29, 2015
To appreciate just how unique West Central Cooperative is in the world of ag retail, an observer need only consider Read More
Winter Wheat
CropLife 100South Dakota Co-op Member Owners Vote No On Unification
June 26, 2015
The Boards of Directors for North Central Farmers Elevator (NCFE) and Wheat Growers (WG) have announced that member-owners have voted Read More
CropLife 100The Andersons Acquires South Dakota Plant Nutrient Manufacturer Kay-Flo
May 20, 2015
The Andersons, Inc., ranked No. 22 on the CropLife 100, has purchased Kay Flo Industries of North Sioux City, SD. “This Read More
CropLife 100AgGateway’s Barcoding Initiative Progressing Nicely
May 8, 2015
According to legend (or Wikipedia), the first step towards modern bar codes came back in 1948, when Bernard Silver, a Read More
CropLife 100Pinnacle Agriculture Acquires Minnesota Retailer
April 14, 2015
Pinnacle Agriculture Holdings, LLC, ranked No. 6 on the CropLife 100,  has successfully acquired Liebl Ag, LLC in Ada, MN.  Read More
CropLife 100CHS, Aurora Cooperative Complete Fertilizer Storage, Grain Shuttle Loading Facility
April 13, 2015
CHS Inc., the nation’s leading cooperative and ranked No. 5 on the CropLife 100, and Aurora Cooperative (ranked No. 21) Read More
Latest News
Agworld Apple Watch Farm Management
EquipmentAussie Data Management Software Company Making Its Mark…
July 4, 2015
Zach Sheely, vice president of sales and operations, says that several large, well-known U.S. cooperatives (Stanislaus Farm Supply, Wilco-Winfield and Read More
Topcon AGI-4 on MF Planter
EquipmentAutosteer: Compatibility, Accuracy Remain Top Of Mind
July 3, 2015
The world of automatic steering solutions in agriculture has evolved rapidly in the last few years. From after-market add-ons that Read More
ManagementUnited Suppliers/Land ‘O Lakes Merger & Crop Update
July 2, 2015
CropLife’s Paul Schrimpf and Eric Sfiligoj talk about the reasons behind the United Suppliers/Land ‘O Lakes merger and USDA’s recent Read More
Industry NewsBioSafe Adds To Sales Force
July 2, 2015
BioSafe Systems has announced the hire of two new members for its service team. David Britt recently joined the team Read More
Chesapeake Bay
ManagementChesapeake Bay Clean-Up Gets Renewed Attention
July 2, 2015
The Chesapeake Bay has been called one of the most biologically productive ecosystems in the world. It’s also one of Read More
Measuring Bulk Tanks
ManagementBulk Pesticide Compliance: Top 10 Areas Of Improvement …
July 1, 2015
  In honor of the 33-year run of David Letterman’s Late Show, the American Agronomic Stewardship Alliance (AASA) is happy Read More
Industry NewsArysta North America Hires Midwest Sales Manager
July 1, 2015
Arysta LifeScience North America recently announced the hiring of Brian Battles as the Senior Technical Sales Manager for the Midwest Read More
Farmer on tablet
Eric SfiligojThe Never-Ending Battle Against Modern Agriculture
July 1, 2015
In the world of comic books, the character of Superman often refers to the fight to save the world as Read More
Retail FacilitiesBuilding Up Ag Retail
July 1, 2015
In the oftentimes unpredictable world we live in, it’s nice to know some things can be reliably countered on to Read More
Retail FacilitiesMaple River Grain And Agronomy Phases In Site Developme…
July 1, 2015
Marcus Construction helped Maple River Grain and Agronomy in Casselton, ND, with the design-build of its dry fertilizer, liquid chemical/seed Read More
Retail FacilitiesA&B Welding Builds A New Liquid Terminal Hub For Br…
July 1, 2015
To build its new hub facility, Briggs Crop Nutrients enlisted the help of A&B Welding. The result, an efficient facility Read More
Edon Farmers Co-op
Retail FacilitiesNew Marcus Facility At Edon Farmers Co-op Provides More…
July 1, 2015
Edon Farmers Co-Op in Edon, OH, needed a new facility to consolidate outdated locations. Marcus Construction was able to design Read More
Retail FacilitiesKinder Morgan Expands Its Storage With A New Dome Barre…
July 1, 2015
Kinder Morgan wanted additional covered storage at its Dakota Bulk Terminal on the Mississippi River in St. Paul, MN. With Read More
Retail FacilitiesHeartland Tank Protects Fertilizer From Extreme Cold At…
July 1, 2015
The Arthur Companies in Harvey, ND, enlisted the help of Heartland Tank Companies to develop a new liquid fertilizer facility Read More
The McGregor Co. fertilizer loadout
Retail FacilitiesThe McGregor Co. Partners With Kahler Automation To Cre…
June 30, 2015
Kahler Automation helped The McGregor Co. expand its Clarkston, WA, operation with unstaffed loadout technology that enables customers to pick Read More
Dry and Liquid Plant
Retail FacilitiesKahler Automation Helps CHS Dakota Ag Cooperative Build…
June 30, 2015
CHS Dakota Ag Cooperative in Mooreton, ND, wanted a liquid/dry blender system that could meet the needs of its customers Read More
Crop InputsLand O’Lakes, United Suppliers To Merge Crop Inpu…
June 29, 2015
Land O’Lakes, Inc. and United Suppliers, Inc. of Ames, IA, today announced their intent to merge their crop inputs businesses. Read More
FungicidesHelena To Distribute Unique Summit Agro Fungicide
June 29, 2015
RANMAN 400 SC fungicide, the only fungicide with a FRAC group 21 designation, is now part of the innovative Summit Read More