From 2015 to 2018, research was conducted on the effects of hail damage on soybean maturity, yield and quality at Portage la Prairie and Minto, Manitoba for a total of five site-years. Three of the five site-years were ironically lost due to actual hail storms.
Soybean Defoliation Results
The objective of this experiment was to determine the effects of defoliation at various timings (V3, R1, R3, R4, R5 and R6 stages) and severity levels (0%, 33%, 66% and 100%) on soybean yield and maturity, and to produce region-specific crop insurance data.
It was found that soybeans at the full pod (R4) and early seed fill (R5) stages were most sensitive to leaf loss, where yield was reduced at all levels of defoliation and losses sharply increased with increasing leaf loss (Table 1). Yield loss was as great as 70-75% at the R4-R5 stages when there was 100% defoliation.
At full seed (R6), yield loss at 100% defoliation was much lower than that at R3 through R5. This tells us that soybeans are more tolerant to leaf loss from the R6 stage onward.
When it came to soybean maturity, they found a 3-day delay in maturity when 100% defoliation occurred at V3 and R1, and a 4-day delay in maturity from 100% defoliation at the R3 stage. However, these maturity delays would not pose an increased risk of fall frost damage to soybeans.
For more information, check out the Soybean and Pulse Agronomy Lab’s 2019 and 2020 Annual Report.
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