# How to estimate your corn yieldsHow to estimate your corn yields

Corn Commentary: How many bushels will you harvest this fall? Here’s a step-by-step refresher for estimating corn yields.

Tom J. Bechman, Midwest Crops Editor

August 20, 2024

5 Min Read
KERNEL DEPTH MATTERS: How deep and plump kernels are significantly affects final yield. In the yield estimation formula, this influences the fudge factor representing kernels per bushel. Tom J. Bechman

For anyone who truly loves growing corn, finding out how many bushels per acre you can expect can be as exciting as Christmas morning! What kind of crop did Mother Nature deliver this year? Indications are that in many areas — except those hit hard by late planting or flooding — the corn crop should be good. The \$64,000 question: How good?

Dan Quinn, Purdue Extension corn specialist, says the best way to answer that question is to walk fields. Quinn provides advice for the Corn Commentary project, which follows the progress of a 45-acre field in central Indiana this season. Use the method Quinn outlines to estimate your yields:

1. Decide on a formula. Quinn relies on the formula explained in the 2024 Purdue Corn and Soybean Field Guide. It is based on average number of ears per acre, rows of kernels per ear, kernels per row and a factor representing the number of kernels per bushel. The formula is: Ear number times (kernel rows times kernels per row) divided by kernels per bushel, known as the fudge factor.

“Traditionally, agronomists assumed 90,000 kernels per bushel volume, so the fudge factor was 90,” Quinn says. “Today, with more modern hybrids, many agronomists use 80. Tweak it depending upon individual hybrids and how well kernels develop during grain fill.”

2. Choose 1/1,000 acre at random and count ears. A rope marked to 17 feet, 5 inches for 30-inch rows or 26 feet, 2 inches for 20-inch rows measures off 1/1,000 acre, Quinn explains. Once the area is marked, count harvestable ears on either side of the rope; then average the numbers.

3. Count rows of kernels per ear and kernels per row. Pull three ears at random within the sampling area. Pull the same ears each time, such as the fifth, 14th and 22nd ears. Determine average number of kernel rows and average number of kernels per row. An alternative method is to pull every fifth ear in the sample area.

4. Estimate yield per location. Suppose you find 31 ears per 1/1,000 acre, 16.3 average rows per ear and 38 average kernels per row. You choose 85 as the fudge factor. The equation becomes:

31 × (16.3 × 38) = 19,201 ÷ 85 = 225.9 bushels per acre, dry corn

5. Repeat the procedure at other locations. Quinn suggests checking at least five spots at random within the field. The more locations you include, the more accurate your estimate.

Suppose you check four more locations. Average yields are 218.6, 234.8, 229.9 and 217.0. Your final yield estimate would be: 225.9 + 218.6 + 234.8 + 229.9 + 217.0 = 1,126.2 ÷ 5 = 225.4 bushels per acre.

## Corn Commentary field

Ear count per acre is uniform in the Corn Commentary field at 32,000 ears, or 32 for 1/1,000 acre. Note that some yield estimation formulas use ear count per acre.

Number of rows per ear averaged 16. The kicker in this field is long ear length, at an average of 42 kernels per ear.

Kernels appear deep. If the field catches late-season rains, set the fudge factor at 80. If not, use 85. Calculations become, with late-season rain: 32 × 16 × 42 = 21,504 ÷ 80 = 268.8 bushels per acre. Without late-season rain: 21,504 ÷ 85 = 253 bushels per acre.

Follow along in future weeks to see if this estimate is accurate.

## Across the rows:Decisions to make before growing season ends

In Ohio. “Storms hit part of the state recently. Yield losses from root lodging where the stalk remains intact are most severe, causing up to 45% yield loss, when it occurs during pollination. Root lodging is less of an issue when corn is at vegetative stages. However, if corn becomes root lodged during the grain fill stages, it may be nonharvestable, resulting in greater losses if the damage is severe and no harvest accommodation can be made to pick ears from plants almost lying flat on a field.” — Osler Ortez, Ohio State University Extension corn specialist, in C.O.R.N. Newsletter, edition 24-27

Nebraska-based research. Researchers in 10 Midwest states cooperated to look at corn maturity using the University of Nebraska Hybrid Maize Crop model. Here are the results. Corn has reached the dent stage in the southern fringe of the Corn Belt, Kansas, Missouri and southern Illinois. Elsewhere, corn has reached dough stage, except for a few sites in the northern region in North Dakota, Michigan and northern Minnesota where corn is still in milk or even blister stage. In general, corn development is ahead relative to the 2023 crop season, except for North Dakota, Minnesota and Iowa where development is similar to last year. ­— from Nebraska Cropwatch, Aug. 7 edition

In Illinois. “Depending upon maturity and planting date, most cornfields visited were R3 to R4 and R4 to R5. An unwelcome discovery this week was significant: tar spot symptoms in several cornfields. The decision to use a fungicide treatment is difficult in later maturity stages, especially when we are near R5, the dent stage. A reminder that grain fill in the dent stage often extends to 30 days or more. However, with declining commodity prices, farmers need to consider their return on investment when considering additional fungicide applications.

“A tool available to aid in the decision-making is the Corn Fungicide ROI Calculator from the Crop Protection Network. The purpose of the Corn Fungicide ROI Calculator is to share results from university uniform corn fungicide trials conducted in the United States and Canada. It allows farmers to calculate the potential ROI for corn fungicide application across a variety of user-defined factors based on research data. The two variables needed are expected corn yield and marketing price.” — Russ Higgins, commercial agriculture educator, University of Illinois Extension, Grundy County, writing in the Illinois Bulletin, Aug. 9 edition, by Farmdoc

In North Dakota. “There is plenty of corn in North Dakota, but there are other important crops too. Here is an update relayed from a farmer in northeast North Dakota on barley harvest: Barley and small grain harvest is officially underway. Crop quality and yield look good so far. They expect wet conditions for the remainder of the week with rain, so might see a short delay. The most notable thing noticed in their fields is some scab issues. Otherwise, they haven’t had many issues with pests or disease on their farm this year.” — Sarah McNaughton, editor of Dakota Farmer

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Yields

## About the Author

Midwest Crops Editor, Farm Progress

Tom J. Bechman became the Midwest Crops editor at Farm Progress in 2024 after serving as editor of Indiana Prairie Farmer for 23 years. He joined Farm Progress in 1981 as a field editor, first writing stories to help farmers adjust to a difficult harvest after a tough weather year. His goal today is the same — writing stories that help farmers adjust to a changing environment in a profitable manner.

Bechman knows about Indiana agriculture because he grew up on a small dairy farm and worked with young farmers as a vocational agriculture teacher and FFA advisor before joining Farm Progress. He works closely with Purdue University specialists, Indiana Farm Bureau and commodity groups to cover cutting-edge issues affecting farmers. He specializes in writing crop stories with a focus on obtaining the highest and most economical yields possible.

Tom and his wife, Carla, have four children: Allison, Ashley, Daniel and Kayla, plus eight grandchildren. They raise produce for the food pantry and house 4-H animals for the grandkids on their small acreage near Franklin, Ind.

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