Hail Damage to Soybean in Reproductive Stages and Options

By Jenny Rees and Justin McMechan et.al

Crop Insurance

The federal crop soybean replant deadline was July 5. Those receiving storms prior to this would have coverage for replant soybean, while those receiving storms after this date will not. Assessment is based on 10 feet of row and determining the original stand and whether the current stand is dead or alive. There are two tables for stand reduction loss assessments. One from VC-R1 and the other from R2-R3.5. Stand reductions from 120,000 to 60,000 plants per acre resulted in an estimated yield loss of 14% from VC to R1 stages and 35% from R2 to R3.5 stages. From what we’ve heard from producers throughout the state, most soybean were at least at beginning flowering (R1) prior to hail damage in recent weeks.  

Estimates are made based on a combination of node cut/broken after the V1 stage and percent leaf defoliation after the R1 stage. A worksheet to estimate total losses is in Evaluating Hail Damage to Soybeans (Nebraska Extension EC128). The following hail damage to soybean assessment video is also a helpful resource.

The development stage at the time of hail also makes a difference. We’re seeing many new flowers occurring on the axillary buds of these mowed off plants. New nodes and flowers continue to develop until R5 (beginning seed). Individual field assessments are needed to determine the potential for regrowth, damage to tops of plants (which may result in increased branching with lower pods instead of top growth).

Options with Additional Considerations

As we approach July 15, the window for replant soybeans making maturity prior to frost is continually reduced. Another problem is that open canopies allow weed emergence. The following are some options for consideration, depending on your specific situation.

1. Leave it alone. This is for those who had minor defoliation or who still have fields with some green leaves and new regrowth. Concerns for those without canopy cover is weed control going forward.
2. Replant soybean. This could be an option when there’s uncertainty of how well soybean will recover and to help with weed control. In the York/Seward county area, this option is being considered for beans that were reduced to sticks with no green leaves and were formerly at R3-R4 development stages. Depending on what crop insurance allows, producers can either split the old row planting beans or could drill beans if allowed. Narrow rows and increasing plant population on replanted soybean allow a fast ground coverage and sunlight capture for the crop. Plant about one inch deep (or into moisture to get germination and quick emergence). Soybeans replanted after July 5 will not be covered by insurance. With this option, one also needs to consider:
   • Additional cost of the seed (or if the replant beans are free from your company), seeding cost of increased seeding rate, and herbicide costs.
   • Add a fungicide seed treatment for protection against phytophthora root rot, as that tends to be a problem in replanted soybean.
   • Increasing seeding rate (seeding 150K or greater) to help with soybean producing higher pods on the lowest nodes and to help with faster canopy closure.
   • Reducing the maturity group at this time of year to help with soybean maturing before the first killing frost for your area of the state. There’s always discussion/disagreement about maturity groups in June/July. Universities recommend going with shorter season maturities instead of longer season ones due to the potential of them not finishing before a killing frost. What one chooses to do is based on the risk one wishes to take. A new tool that can help is CliGrow (although it doesn’t allow you to look at the potential to plant soybean after July 13 in Nebraska).

To demonstrate the differences in this, Dr. Jim Specht ran the SoySim model for Jenny while she was out doing hail damage assessments with growers who experienced hail damage in the York/Seward County area on July 4 and 10. Using historic 2011 to 2022 weather data recorded at the York 2N Station data, SoySim projects 2023 soybean crop development, of which the key date is R7 (physiological maturity — i.e., 95% of the pods will be mature). For the five MG choices planted on July 20, their corresponding expected 2023 R7 dates are shown in the last column of the below table. SoySim also projects the yield potentials that would be possible given the worst and best past historical years, and the “average” year. The key issues are (1) probability of the first killing frost (31F) occurring before each R7 date shown in the table, and (2) reward/risk ratio (hi/low yield) possible for a given MG should that freeze be late in 2023 (i.e, a repeat first freeze occurring of Nov. 2 in 2021) or early (i.e, Oct. 7 in 2022). For reference, the 30-year average first freeze (31°F) in York is Oct. 14.

Table 1. Yield potential of maturity groups planted on July 20, 2023 in the York, Nebraska area.

The following is what Nicolas found using SoySim for the North Platte area using historic 1982-2020 weather data after the hailstorm there. It again shows that reducing maturity by 0.5 units is a good strategy when replanting soybeans in July to potentially achieve physiological maturity without sacrificing yield.

Table 2. Yield potential of maturity groups planted on July 3 in the North Platte, Nebraska area.

3. Plant a forage crop. For this option, the field must be released by crop insurance. You should also check if there are any replant restrictions for seeding a particular cover crop. If you choose to seed a cover crop before the replant restriction listed on the label, the risk is on that individual as to if the cover crop germinates and grows or not. Opportunities exist for warm-season annual forages planted in July or warm-/cool-season forages planted in August. The following BeefWatch article shares annual forage options for July or August plantings. The following forage options after hail damage to crops video shares additional information.