Do pod counts predict soybean yield?
Nobody quotes a pod count when they talk soybean yield. The reason usually given is that pod counts don’t convert — and that is half true. They do not convert through any published formula. But they carry real signal, and it can be measured instead of argued about. So far as we can find, nobody has published the measurement. This is it.
What the tour actually does with soybeans
Pro Farmer’s scouts measure corn as a yield in the field — ear counts, grain length, kernel rows. They never measure a soybean yield at all. The published method is to count pods: “Count all pods on the three plants — any pod ¼″ or larger — and average.” That count is normalised to a three-foot square and published per state. No state soybean yield is published, ever.
Their stated reason is exact, and it is the reason this page has to be careful: “The number of pods it takes to make a bushel is different in each state and varies from year to year.”
The measurement
Twenty-eight state-years: seven tour states, 2022 through 2025. Pod counts as Pro Farmer published them. Soybean yields as USDA NASS finally published them, in the Crop Production Annual Summary each January, cross-checked against the state field-office releases.
Each dot is one state in one year, shown as a difference from that state’s own four-year average. Working within state is not a stylistic choice. Pooling every state together gives r = +0.85, but most of that is just South Dakota having both low pod counts and low yields — it measures the gap between states, not the thing anyone wants to know. Subtracting each state’s own average isolates the real question: when a state’s pod count moves, does its yield move with it?
The corn side of the same tour, run through exactly the same arithmetic, is the control. Shaded band is 95%.
| Fit | n | r | R² | Typical miss | of mean yield |
|---|---|---|---|---|---|
| Pods → soybean yield, within state | 28 | +0.66 | 0.43 | 2.54 bu | 4.6% |
| Tour corn → corn yield, within state | 28 | +0.85 | 0.73 | 4.87 bu | 2.6% |
| Pods → soybean yield, pooled | 28 | +0.85 | 0.72 | 3.95 bu | 7.2% |
| Year-on-year % change in pods | 21 | +0.70 | 0.49 | 5.6 pts | — |
The answer. Pod counts are about 1.8× looser than the tour’s corn reading — a typical miss of 4.6% of mean yield against 2.6%. That is worse, and it is nothing like useless. The tour measures corn directly and never measures a soybean yield at all, so a factor of 1.8 is a small price for a number that is only ever counted, never weighed. Pod counts deserve to be quoted. They deserve to be quoted with a band around them.
The divisor everyone repeats is wrong
The rule of thumb you will hear is “divide the pod count by 27.” It traces to a single 2013 DTN blog post quoting an unnamed source, and the journalist who printed it attached her own warning: “I just wouldn’t put too much stock in that yield estimate’s accuracy.” It is not a Pro Farmer number and never was.
Our twenty-eight state-years put it at 22.0 as a simple ratio of pods to bushels, and 23.5 as the marginal slope of the fit. Both sit inside the 21.8–25.8 range implied by Pro Farmer’s own published national pairs. Three independent routes, one answer, and 27 is not it.
Worth knowing if you are tempted by a textbook: the extension formulas — Purdue, Ohio State, Iowa State, and USDA’s own objective-yield conversion — all give 15 to 18 on this basis. Apply any of them to a Pro Farmer count and you will overstate yield by 55 to 60%, because Pro Farmer counts any pod a quarter-inch or larger off three plants on fields chosen by the route. Different scale, on purpose. Never import those constants.
What would break this
Four years is four years. Leaving any one state out moves the correlation between +0.60 and +0.74, which is stable. Leaving out a year is the worry: drop 2025 and it falls to +0.47. One season is carrying a lot of the signal, which is exactly what four points per state should be expected to do. Extending the panel back to 2016 is the next job, and it is cheap — every Pro Farmer nightly report carries a year-ago comparison, so each one read yields two years of data.
Pod weight compensates, and the tour cannot see it. USDA’s own eleven-state pod counts fell 12.6% from 2018 to 2019 while yield fell only 6.3%, because the average pod got heavier. Seed size alone swings a yield estimate by about 17% with no change in pod count whatsoever. The tour counts pods and never weighs them, so that whole term is invisible to it. This is the structural ceiling, and no amount of extra data removes it.
One state, one year, is a coin flip and a half. On year-over-year change, pod count and yield move the same direction 14 times in 21. The corn control manages 16 of 21. Read a single state’s pod count as a yield signal and you will be right about two times in three.
What we will not do
Print a single number and call it a soybean yield. On this fit the 95% band is roughly ±5 bushels an acre, and pooled it is nearly ±8. A point estimate inside a band that wide is a decoration, not a forecast. When we do publish an estimate it will be a range, it will carry the band, and it will be labelled as ours — a calibration, not a translation of anything Pro Farmer said.
Where the numbers came from
Pod counts: Pro Farmer Crop Tour state results, 2022–2025, as published each night of the tour. Soybean yields: USDA NASS Crop Production Annual Summary, the January-following edition each year, cross-checked against NASS state field-office releases and Executive Briefings. Every cell sourced; none interpolated or filled in. Two cautions we are carrying openly: Ohio and South Dakota 2025 come from the NASS State Agriculture Overview rather than a January field-office release, and NASS revised several 2021 state figures upward between the January 2022 and January 2023 prints — 2021 is not used in any fit on this page. Arithmetic is ours; the underlying figures are not.