Skips in Soybean Rows Cost Yield

Plants compensate if stands are uniform.

Tom Bechman

Published: Jul 19, 2010

Palle Pedersen of Syngenta told Darrell Boone, representing Indiana Prairie Farmer, that 100,000 plants is all you need for maximum yield, That would eman planting 125,000 seeds per acre in 15-inch or 30-inch rows if conditions were excellent, or 140,000 if conditions weren't quite as ideal.

Most farmers would panic at 100,000 plants per acre. Ye4t Pedersen, even though he represents Syngenta, a company that sells hi-tech seed, says that farmers no longer have the luxury of greatly overseeding as insurance. The seed is too expensive to allow that, he notes. He sees no need for stands of 150,000 or more in 15 or 30-inch rows. See the complete story in the August issue of Indiana Prairie Farmer.

His data coincides with what Beck's Hybrids began telling customer s just a few years ago. And it jives with work going back 20 or more years, in which Purdue University soybean researches showed in replicated plots that they could often maintain yields at populations as low as 60,000 plants per acre in 30-inch rows.

All these results always carry a caveat- an asterisk, a footnote. The stand must be uniform. Unless you set out for low populations on purpose, often the stands aren't uniform. The other footnote says that there must be good weed control. That's less of an issue today with Roundup Ready and Liberty Link soybeans. Farmers don't count on crop canopy to shade out weeds as much as they once did.

A field we happened across in Fayette County last week looked good, except there were two-foot skips in one row in place. The beans are past knee-high. The skips weren't all over the field. But what if 2-foot skips were common? What would that do to soybean yield?

Purdue researchers also looked into this question years ago. The data should still hold true today. The following information is taken from the Corn & Soybean Field Guide published by the Purdue Diagnostic Crop Training Center.

If you have 20-foot skips and they make up 50% of the row, you can still expect 94% of normal yield. That's because the soybeans at either end of the skip will branch and compensate for missing plants. Still, if your goal was 50% yield, that's a 3 bushel per acre loss. At $8 per bushel, that's $24 per acre in lost yield gross income off the top.

The condition gets more serious if the skips are longer. If 3 foot skips make up 50% of the row, yield potential drops to 87% of optimum. If there are 4-foot skips making up 50% of the row, it's 85% of original potential yield.

Skips matter, although an occasional skip here and there likely won't be a blip on the yield monitor. It's when you have consistent skips that yield may begin to be affected to some degree.