Several weeks ago, the Illinois Soy Envoys* were discussing what they were seeing in the field. One of them had counted 85 pods on one soybean plant. I once counted 85 pods on a plant from one of the top-yielding soybean fields ever at the Precision Planting PTI Farm in Pontiac, IL. I quickly asked if those pods had three or two seeds in each one. Many of the Soy Envoys said they had been observing mostly “two-seeded pods” in soybean fields across Illinois.

Over the past few weeks, Darby Danzl, regional technical agronomist at Illinois Soybean Association (ISA), and I evaluated several ISA On-Farm Trial soybean plots with different sulfur treatments. I chose two of the plot locations as examples to look specifically at growing conditions and pod count.

Both plots had a high amount of two-pods from the random sample we pulled in each treatment, but both also had a significant number of three-pods plants as well. We found only one four-pod plant in the Knox County plot. The Vermilion County plot had the greatest total pod count. We are quick to blame Mother Nature for the lack of seeds per pod, but genetic and management factors could also play a role. See the photos below – click on each photo to enlarge.

Genetics

Both plot examples included different soybean varieties of the same maturity planted around the same time. Soybeans planted in Illinois are indeterminate, which can offer higher yield potential because they produce more nodes and pods over a longer period and provide greater yield stability by compensating for early-season stress with later pod development. Most commercial soybeans are bred for consistency and yield, and two seeds per pod, most common on middle nodes, are dominant and considered stable or reliable. However, some soybean varieties have the potential to produce one to four seeds per pod, and, if you are lucky, five seeds per pod.

Flowering

Both plots began flowering in mid- to late June. The most critical reproductive stages, R1, R2 and R3, developed in July, which brought significant rainfall along with hot temperatures. Soybeans can abort up to 80% of their flowers, which can affect yield. Two ovules per pod, formed during flowering, are almost always fertilized through self-pollination. The third and fourth ovules per pod may abort if conditions are not ideal.

Management

Soil samples were taken in the spring from each plot. Both appeared to have adequate fertilization and showed no major disease or insect issues. However, if a plant is under stress due to nutrients, disease or insects, the seed number may be limited. Seed development is regulated by hormones, which influence how many seeds mature.

Environment

In 2025, heat, at 95F or above, was more likely to have limited pod set and seed number. Even if a pod formed with three ovules, stressful environmental conditions could cause one to abort, resulting in a two-seed pod. Nighttime temperatures above 85F or below 60F can harm pod set, seed formation and seed size. Depending on the soybean variety, daytime temperatures above 95F can be stressful during flowering and seed fill stages, which may reduce yield. Ultimately, August rains during pod fill (R5-R6), but not after R7 (when one pod is brown), improve seed fill and increase seed size and weight, boosting final yields. Unfortunately, many Illinois soybean fields received little to no rain in August.

Summary

The soybean yield formula is determined by plants per acre, pods per plant, seeds per pod and seed weight. From my own experience, yield is virtually impossible to predict before harvest. So far, yield reports from earlier-planted soybeans are not bad, but not as good as last year. Some farmers are reporting significantly low moisture despite soybeans still having green foliage, pods and stems. To add to that, significantly lower moisture levels, 11% to 8%, are causing header loss, shatter, mechanical damage and further yield reduction.

According to Iowa State University, there is no yield loss at 13% moisture; 1.1% loss at 12%; 2.25% loss at 11%; 3.3% lost at 10%; 4.4 % loss at 9%; and 5.4% loss at 8%. Some suggest harvesting in the early morning, evening or even at night to help boost moisture levels, but in many cases, soybean moisture remains low no matter when harvest occurs. Others may have been lucky to catch late-season rains that could improve soybean moisture content at harvest.

*The Illinois Soy Envoy program is funded by the Illinois Soybean Checkoff.

References:

cli-MATE: MRCC Application Tools Environment, Midwestern Regional Climate Center, Purdue University, https://mrcc.purdue.edu/CLIMATE/

Climate Station Summaries, Illinois State Climatologist, https://stateclimatologist.web.illinois.edu/data/illinois-climate-summaries/

2017 Soybean Growth and Development Guide,” University of Wisconsin–Extension, https://walworth.extension.wisc.edu/files/2021/05/2017_Soybean_GrowthDev_Guide_FINAL.pdf

Soybean Harvest: When the Time Is Right,” Integrated Crop Management, Iowa State University Extension and Outreach, https://crops.extension.iastate.edu/post/soybean-harvest-when-time-right