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Soybean School: Estimating Yield and Scouting for Reoccurring Issues

By: RealAgriculture Agronomy Team

September 21, 2015

View the non-AMP version.

USDA photo by Scott Bauer.

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Pride Seeds’ Dan Foster explains how to estimate soybean yield in this video, shot at Canada’s Outdoor Farm Show.

Estimating yields may be more challenging than some of our other annual crops, but it all boils down to a total number of (viable) seeds in a given area. For soybeans, estimating yield without counting every seed over an acre can be summarized by the following calculation:

Mature soybeans. USDA photo by Scott Bauer.

Pods x Seeds Per Pod ÷ Seed Size Factor  = Estimated Bushels Per Acre

where Pods are counted over 21 inches and:
1 row for 30-inch rows
2 rows for 15-inch rows
4 rows for 7.5-inch rows
Seeds Per Pod are averaged over the sample
Seed Size Factor is determined by the number of seeds per pound

In average Seed Size Factor is around 15, but the factor can fluctuate between 15 (large seed – 2500 seeds/lb) and 21 (small seed – 3500 seeds/lb).

“We are in some areas where it’s starting to get a little bit dry,” says Dan Foster of Pride Seeds, “so we’re starting to lose some seed weight there, shrinking those seed sizes. So in that area, we might go upwards of ’21’ and use that as our dividing factor.”

Foster suggests producers consider downloading the Purdue Extension yield guide for help remembering those numbers. And, since you’re out in your crop anyway, why not do some late-season scouting? Look for glyphosate-resistant fleabane, white mould, cyst nematode pressure and sudden death syndrome.

Purdue Extension Corn & Soybean Field Guide app

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