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

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
HerbicidesScouting Key To Next Season’s Soybean Herbicide Program
August 12, 2014
When growing soybeans, growers need to think ahead to stay one step ahead of weeds. That means examining weed threats and evaluating which herbicides work best. Read More

Trending Articles

Equipment2014 Product Of The Year Voting
September 19, 2014
Many new products were introduced to the ag retail marketplace this year. From this group, CropLife IRON and its consulting partners have selected five finalists for the Product of the Year award. Please cast your vote today to help us determine the winner. 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
CropLife 100CHS To Build $3 Billion Fertilizer Plant In North Dakota
September 5, 2014
The fertilizer plant in Spiritwood will be the single largest investment in CHS history, as well as the single largest private investment project ever undertaken in North Dakota. Read More
EquipmentNew Holland Acquires Miller-St. Nazianz
September 3, 2014
The assets of Miller acquired as part of the transaction will become part of New Holland Agriculture, a CNH Industrial brand, building on a successful four-year partnership between the two companies. Read More
CropLife 100Pinnacle Acquires East Kansas Chemical
September 2, 2014
Ranked 82nd on the CropLife 100, East Kansas Chemical will operate as part of Pinnacle's Performance Agriculture brand. Read More
MAGIE 2014 ShowStopper
EquipmentJohn Deere Again Wins MAGIE ShowStopper Award
August 25, 2014
For the second consecutive year, John Deere was honored at the Midwest AG Industries Exposition (MAGIE) for its new R4045 sprayer. Read More

Latest News

Syngenta
Crop InputsSyngenta Launches Plant Breeding Academy
October 1, 2014
Syngenta announces the release of its Breeding Academy, a global initiative designed to enable the continued development of scientists at Syngenta and beyond. Read More
FertilizerFertilizer Outlook And Technology Conference Set For No…
September 30, 2014
Conference participants can expect to gain perspective on the outlook for agriculture and major fertilizer materials and inputs from industry experts. Read More
MicronutrientsVerdesian Acquires Micronutrient Supplier
September 30, 2014
Verdesian Life Sciences has acquired QC Corp., a producer and supplier of granular and dry micronutrients and ferrous sulfate products. Read More
Eric SfiligojHearing From Young Ag Voices
September 30, 2014
Potential future leaders in ag retail had the chance to shine at the recent Mid America CropLife Association meeting. Read More
WebinarsUpcoming Webinars
September 30, 2014
Register for one of our upcoming Webinars or access our archive of past Webinars to view recordings of presentations that may be of interest to you. Read More
Crop InputsSyngenta Appoints New Chief Operating Officer
September 29, 2014
Jon Parr will succeed retiring COO John Atkin at the end of the year. Read More
CropLife 100South Dakota Wheat Growers To Add Grain-Agronomy Facili…
September 26, 2014
Planned to be constructed in Kennebec, the facility will be located along the soon-to-be rehabilitated line of heavy-rail service from Chamberlain to Presho. Read More
CropLife 100GROWMARK Announces Vice President Appointments
September 25, 2014
Two individuals have been appointed Vice President positions on the GROWMARK executive team. Read More
FertilizerFertilizer Industry Organizations Join Global Alliance …
September 25, 2014
The Fertilizer Institute, the International Plant Nutrition Institute and the International Fertilizer Industry Association are encouraging the industry to promote the proper use of fertilizer products to minimize their environmental impact. Read More
Precision AgARA Organized Precision Forum Hits Capitol Hill
September 24, 2014
The Coalition for the Advancement of Precision Agriculture (CAPA) hosted its inaugural Precision Ag Forum, Sept. 18, in Washington, D.C. Read More
FertilizerFactors To Consider When Placing Fertilizer With Seed
September 24, 2014
The type of crop, fertilizer source, row spacing and soil environment all affect how much fertilizer can be safely applied with seed. Read More
FertilizerSidedressing Manure Into Corn Has Promising Results
September 24, 2014
Applying manure to growing crops can boost yields, reduce nutrient losses and give livestock producers another window of time to apply manure to farm fields. Read More
FertilizerWhen To Sample Manure For Analysis
September 24, 2014
Because the goal is to collect a sample that represents the manure actually being applied, the best time to sample is during loading or field application. Here's why. Read More
Syngenta
Seed/BiotechSyngenta Faces Second Lawsuit Over Agrisure Viptera Cor…
September 23, 2014
A second company has sued Syngenta AG over sales of genetically modified corn seed not approved by China. Read More
StewardshipCover Crops Field Guide For Farmers Expanded
September 23, 2014
Farmers interested in planting cover crops to improve soil health now have an updated and expanded resource in the second edition of the Midwest Cover Crops Field Guide. Read More
HerbicidesArysta LifeScience Launches Contest For Wheat Growers
September 23, 2014
The Flush after Flush Photo Finish contest encourages farmers across the U.S. to participate through Instagram or Twitter using the hashtag #FlushAfterFlush. Read More
FertilizerCF Industries Confirms Merger Of Equals Discussions Wit…
September 23, 2014
CF Industries Holdings, Inc. has confirmed that it is in preliminary discussions with Yara International regarding a potential merger of equals transaction. Read More
StewardshipProgram To Examine Ag-Related Practices, Policies To Pr…
September 22, 2014
A panel discussion on October 14 will include a significant discussion on key issues and solutions related to all aspects of harmful algal blooms. Read More