Unfortunately, over the last two weeks, isolated severe hail storms occurred resulting in hail damage to soybean crops. There is a saying that if hail is going to happen in soybeans then better it comes early rather than late. Manitoba research backs up this rule of thumb. Unfortunately, our current crop is very vulnerable to yield loss from hail damage at this time. Given these points, we need to review what we know about evaluating hail damage in soybeans.
From 2015 to 2018, research to evaluate the effects of simulated hail damage on soybean yield and days to maturity at Portage and Minto, MB was conducted 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 when it came to yield loss. The data from this local research can be used in evaluating the impacts on yield from hail damage.
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.
- Remember that this procedure provides you an estimate only. Each field experiences unique circumstances and the combine remains the final judge.
Remember that days to maturity can also be impacted by hail damage. For instance, in the Manitoba research, 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.