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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter: 2023-06

  1. Topdressing Wheat with Liquid Swine Manure

    Author(s): Glen Arnold, CCA

    With the month of March moving along, the topdressing of wheat fields with nitrogen fertilizer will soon start. Given the current fertilizer prices more livestock producers may be considering applying liquid swine manure as a top-dress for wheat

    The key to applying the correct amount of manure to fertilize wheat is to know the manure’s nitrogen content. Most manure tests reveal total nitrogen, ammonia nitrogen and organic nitrogen amounts. The ammonia nitrogen portion is readily available for plant growth. The organic nitrogen portion takes considerably longer to mineralize and generally will not be available when wheat uptakes the majority of its nitrogen before mid-June.

    Most deep-pit swine finishing manure will contain between 30 and 40 pounds of ammonia nitrogen per 1,000 gallons. Finishing buildings with bowl waters and other water conservation systems can result in nitrogen amounts towards the upper end of this range. Finishing buildings with fixed nipple waters and surface water occasionally entering the pit can result in nitrogen amounts towards the lower end of this range. The contents of the ration fed to the pigs can also affect manure nitrogen numbers.

    In past years, some farmers have used sow manure to topdress wheat. Just know the nitrogen amount in sow manure will be much lower than swine finishing manure.

    In university research, we have used both manure tankers and drag hoses when topdressing wheat. The concern with manure tankers is soil compaction, especially on heavy soils. The drag hose seemed to work well wherever used.

    The typical application rate for liquid swine finishing manure on wheat is 4,000 gallons per acre. Wheat removes 0.49 pounds of P2O5 per bushel harvested. When also harvesting the wheat straw, a ton of wheat straw contains between three and four pounds of P2O5. So, a 100 bushel wheat crop with one ton of straw also removed would withdraw about 52 pounds of P2O5 per acre. This is likely about the same amount of P2O5 as 4,000 gallons of swine finishing manure would contain but review your manure test to make this determination.

    When applying livestock manure to wheat it’s recommended to follow setbacks from ditches and streams. You can check with your local Soil and Water Conservation Service for manure setback distances. Applicators in the Western Lake Erie Basin also need to look at the weather forecast to be certain there is not greater than a 50 percent chance of a half-inch of rain in the 24 hours following manure application when surface applying. Print this forecast so you have proof in the event of a surprise rain downpour.

  2. Battle for the Belt: Episode 2

    Episode 2 of Battle for the Belt is now available:

    Timely corn and soybean planting is necessary to maximize crop yields. For soybean, we have seen approximately a 0.5 bushel per acre per day reduction in yield for each day soybeans were planted after the last week of April. Corn yield reductions can be up to 1.75 bushels per acre per day if planted after the last week of April.

    Although timely planting is essential for both corn and soybean, the weather is often a severely limiting factor. Since 1995, there has been a reduction in suitable days for fieldwork in most Midwestern states, including Ohio (Figure 1). For Ohio, between April 17 to May 15, there has been an average reduction of 0.12 suitable field days per year between 1995 and 2020. Since 1995, an average of 15 suitable days for fieldwork were observed between April 17 to May 15 in Ohio.


    Fieldwork Trends


    With the Battle for the Belt project, we will address planting priority via field research - which crop should we plant first, corn or soybean?

    However, due to sub-optimal conditions in the spring (e.g., wet, cold), we also plan to address the question - which crop has the smallest yield penalty for delayed planting, corn or soybean?

    Besides answering these questions, the Battle for the belt project will help to identify management practices that can help to mitigate yield loss for delayed planting, such as relative maturity adjustments for corn and seeding rate adjustments for soybean.

    Keep following the ‘Battle for the Belt’ project this growing season to learn more. You can access the full video playlist of Battle for the Belt on the Ohio State Agronomy YouTube channel here.

  3. Where Could the U.S.-Mexico GM Corn Dispute End Up?

    Background to the Dispute

    The recent announcement by the Office of the US Trade Representative (USTR) that it was requesting technical consultations with Mexico under the Sanitary and Phytosanitary Measures (SPS) Chapter of the United States-Mexico-Canada Agreement (USMCA), is the latest step in the ongoing dispute over Mexican efforts to ban imports of genetically modified (GM) corn (Office of USTR, March 6, 2023). 

    The dispute has its origins in a decree issued by the Mexican President Andrés Manuel López Obrador on December 31, 2020, calling for GM corn for human consumption to be phased out by the end of January 2024 (Reuters, February 13, 2023).  Not surprisingly, given Mexico is the second-largest export market for US corn totaling $4.792 billion in 2022 (USDA/FAS, 2021) (see Figure 1), with about 17 million metric tons of yellow corn crossing the border annually (USDA/ERS, December 13, 2022), the original decree ratcheted up trade tensions between the two countries.  Following US pressure, Mexico scrapped the 2024 deadline banning GM corn for animal feed and industrial use on February 13, 2023, all the while retaining the ban on its use for human consumption (Reuters, February 13, 2023). 

    Despite these changes, the recent move by USTR is essentially the first step in the process by which the USMCA dispute settlement mechanism is triggered, once other efforts/mechanisms to resolve the issue have failed – specifically, in its response to a letter from USTR, Mexico did not “…allay U.S. concerns with Mexico’s measures concerning [genetically engineered] GE corn….Therefore, the United States does not consider that further use of other mechanisms would resolve the matter…”  (Ambassador Katherine Tai, USTR, March 6, 2023).

    Dispute Settlement under USMCA

    Like the World Trade Organization (WTO), USMCA has a defined legal process by which trade disputes involving its member countries are to be settled.  Once other procedures have been exhausted, technical consultations are the first stage of the process, USTR appealing to Chapter 9 of the USMCA addressing SPS measures,

    “…Pursuant to Article 9.19.2, the United States requests technical consultations with Mexico with regard to Mexico’s measures concerning genetically engineered (GE) corn and certain other GE products.  These measures may adversely affect U.S. trade with Mexico and appear to be inconsistent with Mexico’s commitments under the Sanitary and Phytosanitary (SPS) Measures chapter of USMCA…” (Ambassador Katherine Tai, USTR, March 6, 2023)

    Substantively, USTR is arguing that in seeking to implement its regime on GM corn imports, Mexico is violating its commitment to ensure any SPS measures are “…based on relevant scientific principles…” (Article 9.6.6(b)), and an “…approval procedure that requires a risk assessment…” (Article 9.6.4 (a)). Therefore, the United States and Mexico should meet with “…the aim of resolving the matter cooperatively…” (Article 9.19.3)

     If this fails, under Chapter 31 of USMCA concerning dispute settlement, the United States can seek establishment of an independent panel to investigate and rule on Mexico’s measures relating to GM corn, which, once constituted, would be expected to present its initial report within 150 days (Article 31.17.1).  After a further period of 60 days, allowing for country comments and finalization of the report, the report would be made public (Article 31.17).   Assuming the panel rules against Mexico, resolution of the dispute should then occur within 45 days, Mexico either removing its GM corn measures, providing compensation to the United States, or provision of some other remedy (Article 31.18.2).  If Mexico fails to implement the panel ruling, the United States would be allowed to suspend trade benefits with Mexico equivalent to the damage caused by the latter’s GM corn measures (Article 31.19.1), most likely in the form of a tariff(s) against specific Mexican products.

    How Might a USMCA Panel Rule?

    In thinking about how a USMCA panel might rule, it is important to note the chapter on SPS measures draws heavily on the approach applied in the WTO’s own SPS Agreement, the definitions contained in the latter being incorporated into the USMCA chapter on SPS measures.  Therefore, while the United States is not expected to file a complaint against Mexico under WTO rules, it seems reasonable to argue the 2006 WTO ruling in favor of the United States against the European Union’s (EU) regulation of GM crops would likely influence any USMCA panel ruling.  The WTO panel found the safeguard measures implemented by six EU member states against the import of specific GM crops, were not based on a risk assessment as required under the WTO’s SPS Agreement (Sheldon, Brown Journal of World Affairs, 2007).  In other words, a USMCA panel is very likely to find for the United States against Mexico on the grounds that Mexico has not applied scientific principles and appropriate risk assessment in seeking to ban the import of GM corn.

    Implications for the Ohio Corn Market

    The direct economic impact of not resolving this dispute on the Ohio corn market would likely be modest, given the modest reported value of Ohio corn exports to Mexico over the past two years, as compared to the 10-year average of $6.64 million, and the small proportion of white corn in US corn exports (see Figure 1). Specifically, over the last two years, Mexico accounted for only 2 percent of corn exports from Ohio, while Canada and Asia accounted for the largest shares at 39 and 35 percent respectively (see Figure 2). There are two reasons for these export market shares: Mexico’s import diversification and increased use of Brazilian corn (S&P Global Commodity Insights, December 29, 2022), and strength of the US dollar.

    However, two broader factors could result in substantial indirect impacts on Ohio farmers.  First, there would likely be a “ripple” effect as additional supplies are diverted to the domestic market, driving down corn prices.  As a result, Ohio corn farmers would likely see increased risk of a squeeze on their margins.  Second, and more broadly, if this dispute is not resolved in favor of the United States, it would introduce considerable regulatory uncertainty, with the potential of undermining the stable operation of commodity markets. This could increase the cost of any risk management measures such as hedging and options, placing further financial strain on Ohio grain producers.

    Figure 1. Corn Exports to Mexico (MX)

    Corn to Mexico

    Note: Corn export graphs (bars and scatters) correspond to the left-axis. Exports from US to MX are in billion dollars, and exports from Ohio to MX are in 10 million dollars. The line graph stands for the portion of white corn in total corn exports to MX and corresponds to the right-axis.

     Source: US Census Bureau

    Figure 2. Corn Exports from Ohio

    Ohio Corn to Mexico

    Source: US Census Bureau

    Planning for 2023

    This latest development is another example of volatility in commodity markets and shows how world events impact US and Ohio agriculture.  As you plan for the 2023 planting season, we encourage you to know your cost of production and understand the impact to your returns if the commodity market drops.  How do a five, ten, and twenty percent drop in price impact your bottomline? 

    We encourage you to invest time developing cropping budgets.  If you are looking for guidance in budget development, please see the 2023 OSU Extension Production Budgets available here:

  4. Phosphorus Best Management Practices Field Day

    Author(s): Paige Garrabrant

    Nutrient runoff and algal blooms are a growing problem while fertilizer costs are at an all-time high. Best Management Practice (BMP) Field Day is an event to address these problems and offer solutions for farmers, students, and community members interested in attending. BMP Field Day is a full day event to learn more about Phosphorus usage, the environment, and strategies to save on fertilizer. BMP Field Day will be held in-person March 29th at the Secrest Welcome Center at the Ohio Agricultural Research & Development Center in Wooster, Ohio. Sign-in starts at 8:00 am, the event starts at 8:30 am, and ends at 4:00 pm.


    This event is provided free for farmers, students, and community members because of generous sponsorship from the USDA NIFA and is co-hosted by Virginia Tech and The Ohio State University. Registration includes a free lunch and tour of OARDC field sites. 4.5 CLM and 5.5 CCA credits will be available for attendees. Registration is free but required by March 20th.  For more information and to register, visit .


    BMP Field Day will feature a variety of extension specialists and research scientists with expertise in Phosphorus and how it relates to soil, water, crop health, and more. The afternoon session will feature a Poster & Demo Symposium to showcase strategies to decrease fertilizer usage and costs while maximizing crop growth and protecting the watersheds. Attendees will also be transported on a tour bus to view two of OARDC’s large-scale BMPs: a Sediment Capture and Reuse field site and Smart Drainage Field demonstration.


    Please contact Dr. Catherine Freed ( with any questions or for additional information regarding the event.

  5. Science for Success Webinar: When Early Planting Doesn’t Work Out- Do I Replant, Repair-Plant or Leave this Pitiful Stand?

    Author(s): Laura Lindsey

    Soybean plants have a remarkable ability to compensate for open spaces by developing axillary branches that set additional pods. Learn from our Science for Success team of Soybean Extension Specialists how to assess early season damage and make replanting decisions based on crop conditions and economic considerations so you can save your soybean season. Dr. Shawn Conley, Soybean and Small Grain Extension Specialist from the University of Wisconsin- Madison, will lead the discussion and panelists will include: Dr. Laura Lindsey (Ohio State University), Dr. Manni Singh (Michigan State University), and Dr. Jeremy Ross (University of Arkansas). There will be plenty of time for discussion, so bring your questions!

    When: Friday, March 17, 2023 at 1:00-2:00 PM (EDT)

    Where: Virtual…Register here:

    Cost: FREE! CCAs will earn 0.5 CEUs in Crop Management

  6. Ask the Expert – Managing Frogeye Leaf Spot with Dr. Carl Bradley

    Dr. Carl Bradley

    University of Kentucky Extension Specialist Dr. Carl Bradley recently sat down with us to answer our questions on frogeye leaf spot of soybean. Dr. Bradley is a featured speaker at this year’s Conservation Tillage Conference at Ohio Northern University in Ada, Ohio on March 14-15.

    Q:  What is frogeye leaf spot?
    A:  Frogeye leaf spot is a foliar disease of soybean that is caused by a fungus called Cercospora sojina. It is the most damaging foliar disease of soybean in the U.S. and is most severe when the growing season is warm and humid with plenty of rainfall.

    Q:  What are the management strategies for frogeye leaf spot?
    A:  Integrating different management practices will provide the greatest control of frogeye leaf spot. The primary management strategies are done through planting soybean varieties with a high-level of resistance to frogeye leaf spot, rotating to non-host crops (such as corn), and applying an effective foliar fungicide during the reproductive stages of soybean development.

    Q:  How common is fungicide-resistant frogeye leaf spot?
    A:  Since 2010, fungicide-resistant strains of the frogeye leaf spot fungus have been observed in the U.S. These strains are highly-resistant to QoI fungicides (sometimes called “strobilurin” fungicides), and generally are present anywhere in the U.S. where frogeye leaf spot occurs.

    Q:  Why should I worry about fungicide resistance?
    A:  When a fungal plant pathogen (like the frogeye leaf spot pathogen, Cercospora sojina) becomes resistant to a certain group of fungicides, that group of fungicides will no longer be effective in managing the disease caused by that pathogen. Currently there are only a few different groups of fungicides that are registered for use as a foliar fungicide on soybean. When we lose one of these groups due to fungicide resistance, that leaves fewer effective fungicides available. Overall, this makes management of important diseases much more difficult.

    To learn more about managing frogeye leaf spot and amidst widespread fungicide resistance, attend Dr. Carl Bradley’s presentation at the 2023 Conservation Tillage Conference on Tuesday, March 14 at 10:00 a.m. in the Agronomic Crop Management Session. Register and access the full conference schedule at

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.


Alan Leininger (Educator, Agriculture and Natural Resources)
Amanda Douridas, CCA (Educator, Agriculture and Natural Resources)
Amber Emmons, CCA (Water Quality Extension Associate)
Barry Ward (Program Leader)
Don Hammersmith (Program Assistant, Agriculture and Natural Resources)
Doug Karcher (Chair, Horticulture and Crop Science)
Gigi Neal (Educator, Agriculture and Natural Resources)
Glen Arnold, CCA (Field Specialist, Manure Nutrient Management )
Grant Davis, CCA (Educator, Agriculture and Natural Resources)
Greg LaBarge, CPAg/CCA (Field Specialist, Agronomic Systems)
Jordan Penrose (Educator, Agriculture and Natural Resources)
Kendall Lovejoy (Educator, Agriculture and Natural Resources)
Lee Beers, CCA (Educator, Agriculture and Natural Resources)
Mark Badertscher (Educator, Agriculture and Natural Resources)
Mike Gastier, CCA (Educator, Agriculture and Natural Resources)
Nick Eckel (Educator, Agriculture and Natural Resources)
Osler Ortez (State Specialist, Corn & Emerging Crops)
Pierce Paul (State Specialist, Corn and Wheat Diseases)
Richard Purdin (Educator, Agriculture and Natural Resources)
Ryan McMichael (Educator, Agriculture and Natural Resources)
Stephanie Karhoff, CCA (Field Specialist, Agronomic Systems)
Taylor Dill (Graduate Student)
Ted Wiseman (Educator, Agriculture and Natural Resources)


The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

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