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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter: 2016-25

  1. Estimating Yield Losses in Drought Damaged Corn Fields

    Author(s): Peter Thomison

    Rainfall over the past weekend helped some drought stressed corn fields, especially late plantings, but it may have been too late for others.  Prior to this rainfall, according to the U.S. Drought Monitor, 46 percent of Ohio was rated as in “moderate drought” ( That area covered most of northern Ohio. Another 15 percent was rated in “severe drought”. That area spread from west central Ohio to northeast Ohio.

    Corn growers with drought damaged fields may want to estimate grain yields prior to harvest in order to help with marketing and harvest plans. Two procedures that are widely used for estimating corn grain yields prior to harvest are the YIELD COMPONENT METHOD (also referred to as the "slide rule" or corn yield calculator) and the EAR WEIGHT METHOD. Each method will often produce yield estimates that are within 20 bu/ac of actual yield. Such estimates can be helpful for general planning purposes.

    THE YIELD COMPONENT METHOD was developed by the Agricultural Engineering Department at the University of Illinois. The principle advantage to this method is that it can be used as early as the milk stage of kernel development, a stage many Ohio corn fields have probably achieved. The yield component method involves use of a numerical constant for kernel weight which is figured into an equation in order to calculate grain yield. This numerical constant is sometimes referred to as a "fudge‑factor" since it is based on a predetermined average kernel weight. Since weight per kernel will vary depending on hybrid and environment, the yield component method should be used only to estimate relative grain yields, i.e. "ballpark" grain yields. When below normal rainfall occurs during grain fill (resulting in low kernel weights), the yield component method will OVERESTIMATE yields. In a year with good grain fill conditions (resulting in high kernel weights) the method will underestimate grain yields.

    In the past, the YIELD COMPONENT METHOD equation used a "fudge factor" of 90 (as the average value for kernel weight, expressed as 90,000 kernels per 56 lb bushel), but kernel size has increased as hybrids have improved over the years. Dr. Bob Nielsen at Purdue University suggests that a "fudge factor" of 80 to 85 (85,000 kernels per 56 lb bushel) is a more realistic value to use in the yield estimation equation today.

    According to Dr. Emerson Nafziger at the University of Illinois under current drought stress “…. If there's a fair amount of green leaf area and kernels have already reached dough stage, using 90 [as the “fudge-factor “] might be reasonable. It typically doesn't help much to try to estimate depth of kernels at dough stage, when kernel depth is typically rather shallow anyway, especially if there are 16 or more kernel rows on the ear. If green leaf area is mostly gone, however, and kernels look like they may be starting to shrink a little, kernels may end up very light, and using 120 or even 140 [as the “fudge-factor”] might be more accurate”.

    Calculate estimated grain yield as follows:

    Step 1. Count the number of harvestable ears in a length of row equivalent to 1/1000th acre. For 30‑inch rows, this would be 17 ft. 5 in.

    Step 2. On every fifth ear, count the number of kernel rows per ear and determine the average.

    Step 3. On each of these ears count the number of kernels per row and determine the average. (Do not count kernels on either the butt or tip of the ear that are less than half the size of normal size kernels.)

    Step 4. Yield (bushels per acre) equals (ear #) x (avg. row #) x (avg. kernel #) divided by 90.

    Step 5. Repeat the procedure for at least four additional sites across the field. Given the highly variable conditions present in many stressed fields, repeat the procedure throughout field as many times as you think appropriate, then calculate the average yield for all the sites to make a yield assessment of the entire field.

    Example: You are evaluating a field with 30‑inch rows. You counted 24 ears (per 17' 5" = row section). Sampling every fifth ear resulted in an average row number of 16 and an average number of kernels per row of 30. The estimated yield for that site in the field would be (24 x 16 x 30) divided by 90, which equals 128 bu/acre.

    NOTE: If there is extensive leaf firing and senescence and little green tissue evident, and kernels appear to be shrinking, using 120 or even 140 as the “fudge-factor” might be more appropriate. Making some assessments using both 90 and 120 can provide an idea of the range in yield possible.

    THE EAR WEIGHT METHOD can only be used after the grain is physiologically mature (black layer), which occurs at about 30‑35% grain moisture. Since this method is based on actual ear weight, it should be somewhat more accurate than the yield component method above. However, there still is a fudge factor in the formula to account for average shellout percentage.

    Sample several sites in the field. At each site, measure off a length of row equal to 1/1000th acre. Count the number of harvestable ears in the 1/1000th acre. Weigh every fifth ear and calculate the average ear weight (pounds) for the site. Hand shell the same ears, mix the grain well, and determine an average percent grain moisture with a portable moisture tester.

    Calculate estimated grain yield as follows:

    Step A) Multiply ear number by average ear weight.

    Step B) Multiply average grain moisture by 1.411.

    Step C) Add 46.2 to the result from step B.

    Step D) Divide the result from step A by the result from step C.

    Step E) Multiply the result from step D by 1,000.

    Example: You are evaluating a field with 30‑inch rows. You counted 24 ears (per 17 ft. 5 in. section). Sampling every fifth ear resulted in an average ear weight of 1/2 pound. The average grain moisture was 30 percent. Estimated yield would be [(24 x 0.5) / ((1.411 x 30) + 46.2)] x 1,000, which equals 135 bu/acre.

    Because it can be used at a relatively early stage of kernel development, the Yield Component Method may be of greater assistance to farmers trying to make a decision about whether to harvest their corn for grain or silage. Since drought stress conditions in some fields may result in poorly filled small ears, there may be mechanical difficulties with combine harvest efficiency that need to be considered. When droughts occur, it’s often cheaper to buy corn for grain than to buy hay for roughage (because of likely forage deficits). Therefore, there may be greater benefit in harvesting fields with marginal corn grain yield potential for silage.


    Nafziger, E. 2012. Estimating Yields of Stressed Corn. The Bulletin, Univ of Illinois. [URL checked Aug. 2016].

    Nielsen, RL. 2016.  Estimating Corn Grain Yield Prior to Harvest. Corny News Network, Purdue University. (URL checked Aug. 2016). Note: In this article, Dr. Nielsen also describes the yield estimation method used by the Pro Farmer Midwest Crop Tour which differs from the methods described above.

  2. Screening conservation cover seed for the presence of Palmer amaranth - be informed before you plant

    Author(s): Mark Loux

    The three primary sources of new Palmer amaranth infestations in Ohio so far have been:  1) presence of Palmer seed in the cotton-based feeds that are brought here from the south; 2) movement of contaminated combines from Palmer-infested areas of the south to Ohio; and 3) presence of Palmer seed in seed for conservation plantings (cover crop/CRP/wildlife/pollinator), which comes from states farther west such as Texas and Kansas.  The latter mechanism has gained some notoriety lately in Iowa, where Palmer amaranth was found in conservation plantings in four counties due to the planting of a likely contaminated seed mix.  We currently know of at least two sites here in Ohio where Palmer was introduced this way, one of which resulted in the contamination of several large fields along the Scioto river, and the other where the producer chose to destroy an extensive new conservation planting rather than risk spread to his crop fields.

    Knowing what the sources of palmer amaranth are in theory means that we should be able prevent any additional new infestations.  Wishful thinking, to some degree at least.  Among other things, this would require that every grain or animal producer, feed dealer, and equipment dealer be well-informed enough about this problem to take the appropriate steps: 1) stop importing combines from Palmer-infested areas; 2) stop using cotton-based feed products from these areas; and 3) test all cover crop seed for the presence of Palmer amaranth seed prior to planting.  All of us who provide information know the challenges of getting it to everyone that needs it, not the least of which is refusal of some growers to actually read vehicles such as C.O.R.N.  We can hope that we continue to work toward these solutions before the state gets overrun with Palmer amaranth, but in the meantime here is your chance to be part of the solution now if you are making conservation plantings (assuming that you are one of the informed). 

    OSU, NRCS, and ODA all highly recommend that you take advantage of a free service that ODA is providing to have any seed intended for conservation plantings tested for the presence of palmer amaranth seed at no charge.  That’s right – absolutely free, but the process requires an ODA representative to come to the site of seed storage and take an official sample (rather than sending seed directly to ODA).  Contact David Simmons at ODA for more information at 614-728-6410 or  In addition, we suggest thorough scouting of recently established conservation plantings for the presence of Palmer amaranth.  Any plants found should be cut off below soil line, removed from the area, and composted or burned.  Repeated mowing of infested areas between now and frost can also greatly reduce seed production.  Be aware however that where plants are already producing mature seed (small black seed), mowing will cause further dissemination of seed and the possibility of a more widespread  infestation next year, especially where the cover crops do not completely shade the ground.

  3. Potential for Nitrate Problems in Drought Stressed Corn

    Have very dry soil conditions increased the potential for toxic levels of nitrates in corn harvested for silage? Nitrates absorbed from the soil by plant roots are normally incorporated into plant tissue as amino acids, proteins and other nitrogenous compounds. Thus, the concentration of nitrate in the plant is usually low. The primary site for converting nitrates to these products is in growing green leaves. Under unfavorable growing conditions, especially drought, this conversion process is retarded, causing nitrate to accumulate in the stalks, stems and other conductive tissue. The highest concentration of nitrates is in the lower part of the stalk or stem. For example, the bulk of the nitrate in a drought-stricken corn plant can be found in the bottom third of the stalk. If moisture conditions improve, the conversion process accelerates and within a few days nitrate levels in the plant returns to normal.
    The highest levels of nitrate accumulate when drought occurs after a period of heavy nitrate uptake by the corn plant. Heavy nitrate uptake begins at the V6 growth stage and continues through the silking stage.  Therefore, a drought during or immediately after pollination is often associated with the highest accumulation of nitrates. Extended drought prior to pollination is not necessarily a prelude to high accumulations of nitrate. The resumption of normal plant growth from a heavy rainfall will reduce nitrate accumulation in corn plants, and harvest should be delayed for at least 1 to 2 weeks after the rainfall. Not all drought conditions cause high nitrate levels in plant. If the soil nitrate supply is low in the dry soil surface, plant roots will not absorb nitrates. Some soil moisture is necessary for absorption and accumulation of the nitrates.

    If growers want to salvage part of their drought damaged corn crop as silage, it's best to delay harvesting to maximize grain filling, if ears have formed. Even though leaves may be dying, the stalk and ear often have enough extra water for good keep. Kernels will continue to fill and the increases in dry matter will more than compensate for leaf loss unless plants are actually dying or dead. Moreover, if nitrate levels are high or questionable, they will decrease as plant gets older and nitrates are converted to proteins in the ear.  

  4. Back to the Future with Stink Bugs?

    Some of you may remember the 2012 growing season—very dry most of the year but, in some areas, late season rains gave a second life into the soybean crop that was reaching pod fill stage.  Unfortunately, this boost also likely attracted stink bugs into soybean and robbed many producers of the yield they thought was saved by the rain.  With the recent rains this past week, 2016 is shaping up to be very similar to 2012.  Now that soybean has moisture to fill the pods, we might be seeing a rise in stink bug pressure.  We have already found a few stink bugs in our soybean sweep net surveys in (funded by the Ohio Soybean Council and the North Central Soybean Research Program), so they are active, and will remain active until the R6 stage. The figure shows adult stink bugs that may be found in soybean fields. Soybean fields should be scouted for stink bugs over the next few weeks—start with field edges with 10 sweep sets (10 sweeps per set).  If stink bugs are found, you may want to sample a few areas in the field interior.  Thresholds are set at an average of 4 stink bugs per sweep set, regardless of the species or life stage (e.g. nymph or adult).  If the soybeans are grown for seed or food quality, the threshold is reduced to 2 because of the intense damage directly to the seed. Most of the pressure in found along field edges, so, if threshold is reached, a spray along the edge may prevent most of the damage.  If applications are made, please be aware of honeybees and other pollinators that might still be working the soybean field and always follow the label’s instructions.

  5. Pesticide Disposal Collection Days

    Author(s): Mark Badertscher

    Do you have pesticides sitting in storage that you do not intend to use?  The Ohio Department of Agriculture will be sponsoring four Ohio Pesticide Clean Sweep Days around the state for farmers wishing to dispose of unwanted pesticides on four different dates in August.  The pesticide collection and disposal service is free of charge, but only farm chemicals will be accepted.  Paint, antifreeze, solvents, and household or non-farm pesticides will not be accepted.

    The disposals are limited to farmers only.  Commercial entities are not supposed to bring product.  Pesticides not have to be in original containers or identifiable for disposal.  The largest container that can be accepted is a 55 gallon drum as long as it has a good sealed bung.  There is no limit to the amount of pesticides that a farmer can bring, although ODA would like to know if someone is bringing anything larger than a pickup load.

    The pesticide collections will happen on the dates below from 9:00 am to 3:00 pm at the following locations around the state to allow for local and surrounding county farmers to dispose of these chemicals:

    August 22 - Hardin County Fairgrounds, 14134 County Road 140, Kenton, OH  43326

    August 23 - Guernsey County Fairgrounds, 335 Old National Road, Old Washington, OH  43768

    August 24 - Miami County Fairgrounds, 650 North County Road 25-A, Troy, OH  45373

    August 31 – Huron County Fairgrounds, 940 Fair Road, Norwalk, OH  44857

    Ohio Pesticide Clean Sweep collections are sponsored by the Ohio Department of Agriculture in conjunction with the U.S. Environmental Protection Agency.  To pre-register, or for more information, contact the ODA at 614-728-6987.

  6. Champaign County Precision Ag Day: Planter Technology

    Decisions made at planting time are critical in getting any crop off to the best possible start. The technology and agronomic research we have today can help farmers maximize planter performance for optimal crop yields. Join OSU Extension and Champaign County Farm Bureau on August 26 for the second annual Precision Ag Day. This year the focus will be on planter technology.

    Bill Lehmkuhl with Precision Agri Services Inc, and one of the leaders in planter setup, will be discussing ways to take your planter from beyond the basics. Dr. John Fulton and his ag engineering team at OSU will talk about their multi-hybrid planting experience, provide a UAV update, introduce their new field research app and more. Justin Petrosino, Stewarts Seeds Agronomist, will talk about seed characteristics and selection. Mike Retterer with Pheasants Forever will end the day with a discussion on Maximizing ROI of Planted Acres.

    Hands-on demonstrations with planters will be held by Case IH, John Deere, Sunflower, and Kinze. Everyone will have the opportunity to view two planter setup demos or use the extra time to visit with our vendors which include Apple Farm Service, Farm Service Agency, Koenig Equipment, Integrated Ag Services, Ohio Ag Equipment, Precision Agri Services, Sellman Insurance Group and Tri-County Insurance.

    Certified Crop Advisor Credits offered include 0.5 NM and 3 CM for the entire day. A big thanks goes out to our Lunch Sponsor, Sellman Insurance Group, and our Breakfast Sponsor, Tri-County Insurance Services, LLC. The event is free but RSVPs are required by 8/19 to or 937-484-1526.

  7. Fertilizer Applicator Certification & Training


    A three-hour fertilizer applicator certification training program will be held by The Ohio State University Extension on Monday, August 29, from 6:30 to 9:30 PM at the Palazzo in Botkins, Ohio.  Refreshments will be served at 6:00 PM.  Topics that will be discussed include the current status of water quality, soil sampling, and phosphorus and nitrogen management.  Anyone involved in agricultural production and applying fertilizer to greater than 50 acres must obtain this certification prior to September 30, 2017.  After this date, a test could be required to obtain this certification.  This program is specifically for those individuals not having a pesticide license, although those having a pesticide license may also attend.  Agricultural Professionals please help in reminding your clientele about this fertilizer applicator certification and training program.  Thanks to TruPointe for sponsoring location and refreshments.  Pre-register for the meeting prior to August 26, 2016 by calling the Auglaize County Extension office at 419-739-6580.

  8. FSR Nutrient Management Field Day – September 14

    The FSR Nutrient Management Field Day is September 14th. We will make use of the site and facilities of the Farm Science Review’s Molly Caren Agricultural Center, near London Ohio the week before that event. Check in at 8:30 for a 9 AM start and plan to end the day by 3PM.

    We will break into small groups so you get an up close and personal educational experience for the morning. Starting at 9 AM we will run through the Agronomy Demonstration Plots - the Nitrogen management plots, a Rainfall simulation and Cover crop options. Before lunch we get the rundown on Phosphorus management.

    For the noon meal we have a BBQ box lunch. Then after lunch we will go to larger field demonstrations of fertilizer application – with demonstrations of planter application, delayed application, and methods of incorporation. Then we finish by 3PM with paperwork to secure the Ohio Fertilizer Applicator Certification.

    Cost is $15 per person for the program and includes lunch.

    Register in advance for the program at

    • This event will provide training for the Ohio Agricultural Fertilizer Applicator Certification.
    • CCA CEUs will be available

    The location of the general parking lot of the Farm Science Review is at 445 US 40, London, OH 43140, this is a green grassy area just on the east side of the exhibit grounds – watch for signs.

    This program is supported by the Ohio Soybean Council, the Ohio Corn Marketing Program & the Ohio Small Grains Marketing Program.

    For more information, contact: Harold Watters, OSU Extension,, 937 604-2415 or see

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.


Amanda Bennett (Educator, Agriculture and Natural Resources)
Amanda Douridas, CCA (Educator, Agriculture and Natural Resources)
Andy Michel (State Specialist, Entomology)
Anne Dorrance (State Specialist, Soybean Diseases)
Bruce Clevenger, CCA (Field Specialist, Farm Management)
Ed Lentz, CCA (Educator, Agriculture and Natural Resources)
Eric Richer, CCA (Field Specialist, Farm Management)
Glen Arnold, CCA (Field Specialist, Manure Nutrient Management )
John Barker (Educator, Agriculture and Natural Resources)
Lee Beers, CCA (Educator, Agriculture and Natural Resources)
Les Ober, CCA (Educator, Agriculture and Natural Resources)
Mark Badertscher (Educator, Agriculture and Natural Resources)
Pierce Paul (State Specialist, Corn and Wheat Diseases)
Sam Custer (Educator, Agriculture and Natural Resources)
Sarah Noggle (Educator, Agriculture and Natural Resources)
Steve Culman (State Specialist, Soil Fertility)
Wayne Dellinger, CCA (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.

CFAES provides research and related educational programs to clientele on a nondiscriminatory basis. For more information, visit For an accessible format of this publication, visit