Corn Newsletter : 2015-25

  1. Estimating Corn Yields

    Author(s): Peter Thomison

    This is the time during the growing season when crop tours and seed companies start posting yield predictions for corn. Most of the corn crop in Ohio is probably at the dough stage (R4). Given the tremendous variability in crop quality across the state and between and within fields, it will be particularly interesting this year see how close yield estimates come to matching what's harvested this fall. Moreover, although there may be little or no yield from many fields damaged by excessive rainfall and saturated soil conditions (and related problems, e.g. N deficiency, poorly developed root systems), the fate of other corn fields has yet to be determined. Other factors could cut yields further. Many fields that were excessively wet several weeks ago could now benefit from rain. Shallow, limited root systems attributable to excessive soil moisture may predispose corn to late season soil moisture deficits. Several foliar diseases, esp. northern corn leaf blight and gray leaf spot, are widespread.  Not surprisingly, the predictions I've received thus far indicate a wide range in corn yields.

    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. For more on this check

    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 85.

    Step 5. Repeat the procedure for at least four additional sites across the field. Keep in mind that uniformity of plant development affects the accuracy of  the estimation technique.

    The more variable crop development is across a field, the greater the number of samples that should be taken to estimate yield for the field.

    Example: You are evaluating a field with 30‑inch rows. You counted 29 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 33. The estimated yield for that site in the field would be (29 x 16 x 33) divided by 85, which equals 180 bu/acre.


    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. This will be an important consideration this year given the limited ear development present in many fields exhibiting highly variable plant growth.

    Reference: Nielsen, RL. 2014.  Estimating Corn Grain Yield Prior to Harvest. Corny News Network, Purdue University. (URL checked Aug 2015).

  2. Weather Outlook

    Author(s): Jim Noel

    The outlook for August calls for slightly warmer than normal temperatures and normal and slightly drier than normal. Normal rainfall is about 0.75 inches per week in August.

    As we go into the end of the growing season in September temperatures will likely remain normal or slightly warmer than normal with rainfall normal.

    However, as we get into harvest season indications are it will turn wetter than normal for October and November . This will challenge harvest season again! This will add to an already tough year on Ohio crops.

    All indications are with wetness setting in during fall, the frost and freeze season will likely be later than normal.

    For the latest rainfall 16-day rainfall outlooks from NOAA Ohio River Forecast Center, please visit:

  3. Modified Relay Intercropping Field Day

    On August 26th from 10:00 to 11:45 there will be a field day at OSU Extension Unger Farm, 1303 Bucyrus-Nevada Road, Bucyrus, Ohio 44820. We will be reviewing the research that was done in Modified Relay intercropping last year. We will continue with a plot tour looking at our current research projects including seeding rate, and planting date trials. The field day will finish up by looking at our Intercropping equipment and a discussion on weed control. For more information or to register for the field day contact OSU Extension Crawford County at 419-562-8731 or

  4. Tri-state Yield Monitor Workshop

    A Yield Monitor Data Workshop is scheduled for Tuesday August 25th and Wednesday the 26th in Auburn, Indiana. Steve Miller (MSU) has been coordinating this event - see attached flyer.  This two-day program features John Fulton, Ohio State University Precision Ag specialist and Bob Nielson, Purdue Agronomy corn specialist. This workshop provides a quick overview of precision agriculture then focuses on the basics of yield monitors and what is necessary to effectively use the extensive amount of data generated. Email Steve Miller ( or Lyndon Kelley ( or Call 269-467-5522 with questions.


    • Current State of Precision Agriculture
    • Making Yield Data work for you
    • Precision Ag Technology for On‐Farm Research
    • Yield Monitors—basics of calibration and processing data—data cleaning
    • Hands on working with real data
    • Demos

    Cost is $50.00 per person, includes lunch Tuesday and Wednesdays and refreshment breaks. Location is the 4-H Exhibit Hall at the DeKalb County Fairgrounds, 708 S Union St, Auburn, IN 46706.

    Workshop flyer

  5. Fertilizer Applicator Certification Training Field Day

    Author(s): Amanda Bennett

    A three-hour fertilizer application certification program for any applicator that does not have a pesticide license will be offered on August 27, 2015 from 8:45 a.m. to 12:30 p.m. at Dulls Homestead, Inc. at 10404 National Rd, Brookville, Ohio 45309. The morning will include topics on phosphorus and nitrogen recommendations, soil sampling, assessing nitrogen usage of corn in the field and looking at timing and placement of manure applications for maximized economic return. Certified Crop Advisor (CCA) and Ohio Certified Livestock Manager (CLM) credits will be available. Pre-registration is preferred and you can register by calling the Miami County OSU Extension office at 937-440-3945 or the Montgomery County OSU Extension office at 937-224-9654 x109 or emailing or Find full agenda here.          

    Agricultural fertilizer applicator certification is required for farmers who apply fertilizer to more than 50 acres of agricultural production grown primarily for sale. Farmers who have their fertilizer applied by co-ops or custom applicators are not required to be certified.  Those who have a pesticide applicator license need to attend a two-hour fertilizer certification. If an applicator does not have a pesticide license, they will be required to attend a three-hour fertilizer certification. The Ohio Department of Agriculture is the agency issuing the certification for agriculture fertilizer applications. Their website has information regarding the regulation at  For more information about other training sessions or general materials for the agriculture fertilizer certification, visit

  6. Editor's Note

    In last week’s article: “Pricing Corn Silage Update” the step 4 the sentence should have read “based on current market values…”, instead of “based on nutrient values…”

About the C.O.R.N. Newsletter

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.


David Dugan (Adams County)
Debbie Brown, CCA (Shelby County)
Ed Lentz, CCA (Hancock County)
Glen Arnold, CCA (Field Specialist, Manure Nutrient Management )
Greg LaBarge, CPAg/CCA (Field Specialist, Agronomic Systems)
Harold Watters, CPAg/CCA (Field Specialist, Agronomic Systems)
Jeff Stachler (Auglaize County)
Les Ober, CCA (Geauga County)
Mark Badertscher (Hardin County)
Mary Griffith (Madison County)
Mike Gastier, CCA (Huron County)
Sam Custer (Darke County)
Steve Culman (State Specialist, Soil Fertility)


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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