How much yield loss can you expect once your soybeans have been hit by hail?
From 2015 to 2018, research was conducted to evaluate the effects of simulated hail damage on soybean yield and days to maturity at Portage and Minto, MB by Kristen MacMillan, UM-MPSG Agronomist-in-Residence. Soybeans at the full pod (R4) and early seed fill (R5) growth stages were the most sensitive to leaf loss and stem breakage.
To estimate yield loss following hail:
- Assess plant stand loss, if any. Plants can regrow from axillary buds on remaining stem nodes.
- Estimate percent stem breakage. At R1, plants often have 5 nodes (4 trifoliate nodes and one unifoliate node). Stem breakage = nodes removed / total nodes the crop had before hail.
- Estimate percent defoliation of remaining plant tissue. Is it closer to one-third, two-thirds or 100% of leaf material lost?
- Using the chart below, add the loss percentages of defoliation and stem breakage together to estimate yield loss.
Days to maturity may also be impacted by hail damage. At R1, 100% defoliation caused a 4-day delay in maturity, while other defoliation severity levels did not impact maturity. At R1-R2, 60-80% node removal resulted in a 4 to 6-day delay in maturity, while 20-40% node removal matured 2 to 3 days later than plants with no damage.
Soybean Yield Response to Defoliation and Node Removal – Research Reports from the Soybeans and Pulse Agronomy Lab →
Case Study from the Field: Soybean Regrowth Following Hail Damage
Last summer, many fields were caught in the crosshairs of various hailstorms. We followed one field through the rest of the summer to observe regrowth potential.
Hail occurred on June 28 and estimates were made the following day. Soybeans were flowering at the time (R1-2) and were left with one, two or no trifoliate leaves remaining per plant and one to two nodes were broken off at the top of the plant. Damage was fairly even throughout the field. Comparing to healthier plants near the shelterbelt, 66-100% defoliation and 20-40% stem breakage occurred, on average. Luckily, very little plant stand loss was observed in the field and plant stand remained at roughly 160,000 plants/ac.
Looking to the research results to estimate yield loss, losing two-thirds of the leaves at R1 resulted in 16% yield loss, while complete defoliation caused 40% yield loss in the small-plot research. For stem breakage at R1-2, losing one node (20% breakage) resulted in 2% yield loss and 8% yield loss when two nodes were broken (40% breakage). Adding those numbers together, and we were anticipating yield losses of 18-24% in the least damaged areas and losses as great as 48% for those beans hit with the worst of the storm.
Revisiting the field throughout the growing season showed the impressive capacity soybeans have to compensate in their growth through branching and increasing number of pods per plant and the number of seeds within those pods. By mid-August, the crop canopy was thick with branches and leaves at R5-6. The only downside was these beans were 12-14” tall and late-emerging weeds had taken advantage of those mid-season openings in the damaged canopy.
In terms of maturity, it looked like these hail-damaged soybeans were about a week to 10 days behind other beans in the area. And as the season progressed the maturity delay become more apparent. Using the small-plot research results, based on the timing of hail and severity of damage, roughly an 8 to 10 day maturity delay would have been expected.
Come early September, plants were at R6.5 with 37 pods per plant and 2.7 seeds per pod, on average. Previous research by Kristen MacMillan has also outlined average yield components for Manitoba soybeans, finding 29 pods per plant and 2.3 seeds per pod on average. These hail-damaged soybeans compensated for the hail damage, in part by increasing these two yield components.
Pre-harvest weed control was necessary to manage green weed material and the field was harvested in mid-October after some weather delays.
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