When an agronomist explains the dynamics of high soybean yields for an hour and then looks at the audience and says, “If you don’t remember anything else, remember these two points,” you know it’s time to listen. That’s especially true if the agronomist is Glenn Longabaugh, who has over three decades of experience in the seed, crop protection and soil fertility business.

Farmers paid attention when Longabaugh spoke recently. He’s an agronomist with WinField United Ag. Here are the two key points he believes anyone seriously searching for high soybean yields should understand.

1. You have all kinds of potential in terms of pods at the R3 stage.

“It’s all about the R3 stage if you’re after high yield,” Longabaugh emphasized. “What happens at this stage is crucial.”

According to the Purdue University Corn & Soybean Field Guide, R3, also called the beginning pod stage, occurs when a pod is 5 millimeters long at one of the four uppermost nodes on the main stem with a fully developed leaf. Translated, flowering is wrapping up and tiny pods are appearing at each node.

“There are more pods present at that stage than you could ever need to reach a very high yield potential,” Longabaugh said. What typically happens is the plant aborts many tiny pods. In fact, he said 60% to 80% of the pods may never develop.

How can you keep plants from aborting pods? Longabaugh said that’s the question to ask. Is it a matter of making sure soil fertility is adequate, including macro-, secondary and micronutrients? Is it a matter of doing what you can to make sure plants aren’t under stress?

He believes all those things likely play a role. It’s a pivotal point in determining final yield potential.

2. Most photosynthesis that will fill pods at any node happens in the leaves attached to that node.

So what about nodes lower on the plant? How can their leaves get enough sunlight to make enough sugars to fill pods? “Look at a plant and see where leaves feeding that node are located,” Longabaugh said. Typically, a very long petiole extends upward, with leaves on the end. Photosynthesis producing sugars to fill those pods occurs on the leaves at the end of that petiole.

“Petioles are complicated structures and require a lot of energy to make,” he said. “But they’re necessary so lower pods have the opportunity to form beans.”

If you understand this concept, you understand how important light interception is to high-yielding soybean plants, Longabaugh pointed out. And if you understand how important light interception is, you realize plants don’t need a huge structure, super height and tons of vegetation to produce top yields. Instead, they must be able to capture light to get products of photosynthesis to each node.

The most productive part of the soybean plant is usually from the seventh through 13th node above the ground, Longabaugh said. “If you pull into a field at harvest and see pods filled out to the top, you’re going to see high yields,” he concluded.