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Soybean Watch: Are the middle parts of your plants loaded with nodes, flowers and pods?

Tom J Bechman 1, Editor, Indiana Prairie Farmer

August 19, 2022

3 Min Read
flowering soybean plant
POD PROSPECTS: You should be seeing lots of flowers and pods in the middle part of the soybean canopy. Agronomist Steve Gauck says it’s the sweet spot that delivers big yields. Tom J. Bechman

There are more things to look for in your soybean fields this time of year than just diseases and insects. Steve Gauck advises spending time walking fields to see just how big your soybean factory has become. Is it big enough to produce 75-bushel soybeans if the weather cooperates?

“Brush back plants and look down inside that canopy,” says Gauck, a regional agronomy manager for Beck’s, sponsor of Soybean Watch ’22. “How dense is it?”

Related: It’s total leaf loss that matters, not holes

Gauck isn’t talking about how many leaves are inside, although you need adequate leaf area to capture as much sunlight as possible. Instead, he’s referring to how many nodes, blooms and pods are in the center portion of each plant. Did plants branch out? If so, how close are nodes with blooms or pods on the branches?

“Well over half of the total soybean yield typically comes from that middle portion of the plant,” Gauck says. “Agronomists estimate that well over 50% of yield comes from nodes six through 13 on a soybean plant. If that’s the case, you need lots of blooms and/or pods on each node.”

Understanding growth stage

You also need as many nodes as possible, Gauck says. If there is a shorter distance between nodes, with a higher number of total nodes per plant, odds favor better yields.

It’s simply a matter of math, he says. More nodes mean more beans per plant. More beans per plant mean more bushels per acre. In fact, some agronomists today think in terms of nodes per acre, Gauck says.

“They evaluate potential soybean management practices to determine which might produce the most nodes per acre,” he explains. However, that’s not always the same as the most plants per acre.

“We’ve found that stands of 80,000 plants per acre can still yield 100% of yield potential,” Gauck says. “You may be able to go as low as 70,000 plants per acre and still reach maximum yield potential. The secret is that when plants are less crowded, they produce more branches. As long as nodes are relatively closely spaced on branches, you’re going to get more beans per plant compared to plants which are thicker but don’t put on as many branches.”

Whether you see blooms or small pods this time of year will depend on the growth stage of the plant, Gauck says. Also, you may find plants with pods forming at lower nodes that are still growing vegetatively and producing more nodes and potential pods at the uppermost nodes.

“If you get timely August rains, pods which form late add yield,” he says. “Most places didn’t see much rain in August in 2021, and many of the uppermost pods aborted. Yields were still respectable, but we didn’t see the yield kick we might have seen if more areas had received timely rains.”

According to the Purdue University Corn & Soybean Field Guide, soybeans are at R4 if there is a pod about three-quarters inch long at one of the four uppermost nodes of the plant. At R5, there is seed about one-eighth inch long inside pods at one of the four uppermost nodes.

About the Author(s)

Tom J Bechman 1

Editor, Indiana Prairie Farmer

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