Article by Kent Wolfe
Crop Sales Specialist
AGRIS Co-operative, DUTTON
As harvest season approaches, it's natural to rely on the combine to tell us how our crops are performing. However, this year, you might want to get ahead of the game by conducting some pre-harvest yield estimates. The primary reason for doing this is to help develop yield estimates for your grain marketing plans. Wanting to forward contract grain requires a level of comfort knowing that we in fact will have the grain to cover the contracts. Having an accurate estimate of your crop yield can provide peace of mind, ensuring you have enough grain to meet your commitments.
There are various methods to estimate yields for corn and soybeans, but I prefer the following simple formulas. Remember that these calculations should be treated as estimates or "ballpark" figures due to field and environmental variability.
Corn Yield Estimate
To estimate corn yield, use the following formula: Average cob length (inches) x kernels per inch x average rows per cob x plant population ÷ kernels per bushel = dry bushels per acre
Example: (7.25” x 5 x 16 x 30.5) ÷ 90 = 196.56 bu/ac
Steps:
- Determine Plant Population: Count the number of plants in 1/1,000th of an acre. Refer to the table below for the length measurement based on your row width:
| Row width (INCHES) |
LENGTH EQUAL TO 1/1,000/A |
| 20" |
26'1" |
| 28" |
18'8" |
| 30" |
17'5" |
| 36" |
14'6" |
| 40" |
13'1" |
- Select Sample Cobs: After calculating population, choose the 3rd, 7th, 11th, and 22nd cobs within the 1/1,000th acre for your kernel counts.
- Measure Cob Length: Count the number of rows around the cob (always even numbers, e.g., 14, 16, 18). Measure the length of the cob in inches, excluding any small tip kernels that may not make it through the combine. The typical number of kernels per inch is 5, but this can vary by variety.
- Adjust for Kernel Size: The divisor represents kernels per bushel. While this can vary, using 90,000 kernels per bushel as an average is a good starting point. For greater accuracy, check multiple locations in your field, considering any variability.
Soybean Yield Estimate
For soybeans, use the following formula: Pods x seeds per pod ÷ seed size factor = estimated bushels per acre
Example: (425 pods x 2.5 seeds per pod) ÷ 18 (normal seed size) = 59.03 bu/ac
Steps:
- Count Pods: For 30-inch rows, count pods in 1 row over a 21-inch length. For 15-inch rows, count 2 rows over the same length, and for 7.5-inch rows, count 4 rows over 21 inches. This method represents 1/10,000th of an acre.
- Adjust for Row Width: If you have a different row width, divide 627.26 by your row width (in inches) to calculate the linear length of 1 row that equals 1/10,000th of an acre. For example, with an 18-inch row width, you'd need to measure 34.8 inches of 1 row.
- Estimate Seeds per Pod: Seed counts can vary, typically ranging from 0 to 5 seeds per pod. A good starting point is 2.5 seeds per pod.
- Adjust for Seed Size: Use the following table to adjust your seed size factor:
| SEEDS PER POUND |
SEED SIZE FACTOR |
| 2500 (large seed) |
15 |
| 2666 |
16 |
| 2833 |
17 |
| 3000 (normal seed) |
18 |
| 3166 |
19 |
| 3333 |
20 |
| 3500 (small seed) |
21 |
Join the Great Lakes Grain Crop Tour
Estimating crop yields before harvest is not a new practice. It has been a long-standing tradition in the U.S. with the Pro Farmer Midwest Tour. Here in Ontario, representatives from your local AGRIS branches will be teaming up with Great Lakes Grain, FS PARTNERS, and Coop Embrun for the 15th Annual Great Lakes Grain Crop Assessment Tour. This event will take place from August 26th to September 6th, with results announced on September 10th at the Canadian Outdoor Farm Show in Woodstock.
If you'd like to participate, register your field!
Sign up