Estimating yields ahead of time: Best methods for corn, soybean crops


Best methods for corn, soybean crops

Tony Nye - OSU Extension



The devastation from the severe derecho storm experienced by our farm families to the West in parts of Indiana, Illinois and of course a large portion of Iowa is just gut wrenching.

I have several farm friends in the areas that have been impacted, and I can tell you the pictures that you have seen on the news and social media are real. We won’t really know the extent of the overall crop damage for a few weeks, but we are already seeing the grain markets responding in a positive direction for the rest of us.

So, my silver lining this week is the potential for our current growing soybean and corn crop.

Thursday of this week my daughter Celeste and I and regional agronomist Elizabeth Hawkins went estimating yields in different areas of Clinton County — in the Melvin/Wilmington area, the Midland/Westboro area, and the Lees Creek area.

When one thinks that our Clinton County corn crop was planted over a five- or six-week period (late April into early June) and our soybean planting season did not end until sometime in June, it’s remarkable how good our crop looks from the road.

On Thursday we were even a bit surprised by the estimates we were getting in some fields of corn with estimated yields of 211 to 260 bushel per acre.

Soybean estimates are more unreliable and harder to get a good handle on potential yield, but the estimation tools we have available allowed us to get estimates of potential soybean yields from 42 to 75 bushel per acre utilizing one calculation and 49 to 87 bushel per acre utilizing another calculation.

Another positive observation in all the fields we were in on Thursday was there was very little disease or insect activity which can always impact yield.

I am sure we will have lesser yields in certain fields throughout the county due to all the factors that can impact yield such as planting date, adequate fertility and rainfall, soil conditions and on and on.

I encourage you get out and do some yield checks in your own fields. The following information will provide you guidance to get some estimated yields for your crops as we get closer to harvest this fall.

Estimating corn yields

We used the yield component method which 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.

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.

To use the yield component method to estimate your corn yield, use the following steps.

• 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 (the fudge factor).

Estimating soybean yields

We used the following soybean formula to get our yield estimates earlier this week:

1. To calculate plants per acre, count the number of pod-bearing plants in 1/1,000th of an acre. In 7.5-inch row spacing, count the number of plants in 69 feet, 8 inches of row. In 15-inch row spacing, count the number of plants in 34 feet, 10 inches of row. In 30-inch row spacing, count the number of plants in 17 feet, 5 inches of row.

2. To 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.

3. To 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.

4. To 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, the following 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]

If you need help in your fields just let me know and I would be glad to assist. Happy yielding!!

Tony Nye is the state coordinator for the Ohio State University Extension Small Farm Program and has been an OSU Extension Educator for agriculture and natural resources for over 30 years, currently serving Clinton County and the Miami Valley EERA.

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Best methods for corn, soybean crops

Tony Nye

OSU Extension