The Difference 4 Days Can Make

Hail Damage in Soybeans

“If hail is going to happen in soybeans, then it is better if it comes early rather than later in the growing season.”

A large storm on July 5, 2026 with golf ball-sized hail, did major crop damage near Wawanesa.

On July 9, this soybean field (looking west) appeared to have almost 100 per cent leaf material loss.

Just four days later on July 13 (looking west), I was happily impressed and new trifoliate leaves from several nodes could be seen on many plants.

Back on July 9, most plants had no top leaves and the stems were broken high up on the plants.

On July 13, the trifoliate leaves had regrown from auxiliary buds on the remaining stem nodes and flowers could be seen! Note the browning hail wounds on the stem and stem breakage.

Back on July 9 (looking along the row), it seemed that almost every leaf had been stripped from the plants and littered the ground.

On July 13, it was easier to tell where the height of the stem breakage had been but trifoliate leaves had grown back.

On July 9, a side view of the rows.

On July 13, a side view of the rows.

How Much Yield Loss Could We Expect From This Level of Damage?

Let’s look to research done nearby at Minto and Portage la Prairie by Kristen MacMillan, over a three-year period that started in 2015. She simulated hail damage at various soybean growth stages and measured the final yield.

To estimate yield loss following hail:

1. Assess plant stand loss, if any. Plants can regrow from axillary buds on remaining stem nodes.
2. Estimate percent stem breakage. At R1, plants often have five nodes (four trifoliate nodes and one unifoliate node). Stem breakage = nodes removed / total nodes the crop had before hail.
3. Estimate percent defoliation of remaining plant tissue. Is it closer to one-third, two-thirds or 100 per cent of leaf material lost?
4. Using the chart below, add the loss percentages of defoliation and stem breakage together to estimate yield loss.
5. Remember that this procedure provides you an estimate only. Each field experiences unique circumstances and the combine remains the final judge.

In the Manitoba research, at R1, 100 per cent defoliation caused a four-day delay in maturity, while anything less than 100 per cent defoliation did not impact maturity. At R1-R2, 60 to 80 per cent node removal resulted in a four to six-day delay in maturity, while 20 to 40 per cent node removal matured two to three days later than plants with no damage.

Using the above pictures as an example:

Let’s say the field was almost at R1 when the hail hit.

TO ESTIMATE possible per cent Yield Damage in our example

1. Most plants seemed to have survived, let’s call it zero per cent plant loss
2. Estimate stem breakage: It is tricky to come up with an average because there is a lot of variation but I would say at most maybe two nodes. They would have had five nodes at the time of the hail. 2/5= 40 per cent
3. Leaf defoliation was close to 100 per cent
4. Consult the chart above. Estimate yield loss by adding:
   • 40 per cent yield loss from 100 per cent defoliation at R1 + 8.2 per cent yield loss from 40 per cent node loss = 48.2 per cent of estimated yield loss
     • If I overestimated, and instead it was 66 per cent defoliation and 20 per cent node loss, then the estimated per cent yield loss would be only 17.4.
     • From Seed Manitoba the 2024 weighted average yield for all soybeans in Manitoba was 45.5 bushels per acre, let’s use that.
     • We could estimate a yield of around 24 bu/ac – 38 bu/ acre
     • These estimates are only estimates! Like my Grandma always said “time will tell”

We could potentially see this example field take as many as four days longer than normal to mature.