By Harold Watters, Ohio State University Extension agronomist
I think this is a year of “I’ll take what I can get” on yield, but still it’s good to know so you can plan ahead for grain sales or feed supplies. By Aug. 10 or so we should be far enough along in the crop season to get a reasonable yield estimate for corn and maybe some inkling for soybean. So how do we check crop yield?
For corn, this from the Corn, Soybean, Wheat and Forages Field Guide page 14, by Peter Thomison retired OSU state corn specialist.
There are several techniques for estimating corn grain yield prior to harvest. A numerical constant for average kernel weight is figured into the equation. Weight per kernel will vary depending on hybrid and environment; yield will be overestimated in a year with poor grain fill conditions and underestimated in a good year.
Step 1. Count the number of harvestable ears in 1/1000th acre. For 30-inch rows that is 17 ft, 5 inches in length. So you need a tape measure for this part; for the rest a pen and paper.
Step 2. Count the number of rows per ear on every 5th ear. Calculate an average.
Step 3. Count the number of kernels per row on those same ears. Do not count kernels on either the butt or tip that are less than half size. Calculate an average.
Step 4. The equation. Yield in bushels per acre equals: ear number multiplied times the average row number times average kernel number, all divided by 90. Or (ear # x row # x kernel #)/90 – estimated yield in bu/A.
From my previous use, this can be right on the money. Don’t forget that you need to check more than one place in the field, check 15 to 20 places and you will be pretty accurate.
For soybeans, from Laura Lindsey OSU’s state soybean specialist. Page 139 in the Field Guide. To estimate soybean yield:
- Calculate plants per acre. Count the number of pod-bearing plants in 1/1,000th of an acre. In 15-inch row spacing, count the number of plants in 34 feet, 10 inches of row (or two rows for 17 feet 5 inches).
- Estimate pods per plant. Count the number of pods (containing one or more seeds) from 10 plants selected at random. Divide the total number of pods by 10 to get the average number of pods per plant.
- Estimate the number of seeds per pod. Count the number of seeds from 10 pods selected at random. Generally, the number of seeds per pod is 2.5, but this number can be less in stressful environmental conditions. Divide the total number of seeds by 10 to get the average number of seeds per pod.
- Estimate the number of seeds per pound (seed size), assume that there are 3,000 seeds per pound. If the soybean plants experienced stress, seed size will be reduced, and it will take more seeds to make one pound. Use a seed size estimate of 3,500 seeds per pound if smaller seeds are expected because of late season stress.
Using the above estimates, this formula is used to estimate soybean yield in bushels per acre: bushels per acre = [(plants/1,000th acre) x (pods/plant) x (seeds/pod)] ÷ [(seeds/pound) x 0.06].
Good luck. Let’s hope for rain while we still have a growing season left.