The value of soybean seed has increased over the years as value-added traits have been introduced. As additional dollars are invested in a unit of soybean seed, it becomes more important to ensure as many seeds as possible will be able to germinate and grow. There are multiple best management practices Golden Harvest uses to ensure every unit has the best possible seed quality. Seed quality can be influenced by uncontrollable factors such as seed production field growing conditions, but with good seed quality testing protocols to identify the best lots and good seed handling procedures, it is possible to provide seed with higher germination rates. The industry standard warm germination rate is 85%, while Golden Harvest strives to offer 90% germination rates for all soybeans.
Seed Quality and Growing Environments
Figure 1. Precipitation map from October 2021; Precipitation Map Source – High Plains Regional Climate Center, https://hprcc.unl.edu/.Soybean seed quality is strongly influenced by growing conditions in the year of seed production. Factors such as drought, temperature, photoperiod length, solar radiation, pesticide metabolism and nutrient availability all play a role in the soybean seed maturation process.
Seed quality is also directly affected by temperature, relative humidity and seed moisture at harvest. The time taken to harvest the soybean seed crop, along with harvest conditions, can impact final seed quality. The 2021 growing season was an example of how weather throughout soybean maturation negatively impacted seed quality across most industry soybean seed production areas. Abnormally wet conditions throughout October (Figure 1), were followed by rapid seed dry-down and harvest moistures below the ideal range of 11%-15%. Rapid soybean seed dry-down often causes wrinkled seed coats (Figure 2) and make seed more susceptible to mechanical damage (Iowa State University).
Mechanical Damage from Seed Handling
Soybean seed is more susceptible to mechanical damage than most other crops. Post-harvest handling of soybeans can further contribute to seed quality issues, such as damaged seed coats, lower germination and poor seed appearance. Damage can occur at multiple points of time through harvesting, seed bagging, delivery and storage. Damage can vary from variety to variety ranging from split cotyledons to invisible microscopic fractures in the seed coat and embryo. Understanding soybean seed quality levels and handling seed appropriately will help maximize seed quality at planting.
Figure 2. Soybean seed with some wrinkled and split seed coats.Golden Harvest recommends multiple methods to reduce mechanical damage to soybean seed:
- Minimizing the number of times seed is handled
- Reducing the height of seed drop to no more than 24 inches
- Lowering the speed of conveyor belts to less than 300 feet per minute
- Avoiding seed contacts with conveyor head as it discharges from the belt
- Moving seed more horizontally than vertically
Downstream Seed Treating
Fungicide seed treatments can help protect against seed- and soil-borne pathogens but requires additional handling for application, which can be another source of mechanical damage if not handled correctly. The following tips can help ensure seed quality is maintained when treating seed.
Figure 3. Buildup from seed coats from treated, fragile soybean seed.- Use recommended seed treating equipment
- Use treaters with primary (atomization) and secondary application (gentle redistribution) to reduce slurry volumes and apply more evenly across seeds.
- Utilize belted conveyors rather than augurs for more gentle handling and reduce splits.
- Decrease drop-height of drop-down ladders to 2 feet or less to minimize damage.
- Optimizing settings on treater
- Calibrate and apply at lowest slurry volume possible to achieve good coverage and maximum efficacy with minimal rewetting of seed.
- Maximize seed flow through treaters to ensure that seed is not hitting the drum directly, causing abrasion.
- Gently transfer seed to boxes or bulk seed handling equipment.
- Use conveyors, not augurs, for loading planting equipment.
- Use drop-down or ladder devices to avoid long drops in tenders, trucks, and boxes.
If there are issues with larger deposits in the seed treater (Figure 3), check atomizers more frequently. Additionally, the drum or bowl of the treater may need to be cleaned more often. There are risks associated with downstream seed treatment. The risk of this additional handling is typically outweighed by the advantage gained in protection from seedling diseases and insects. For a successful planting season, awareness of seed treatment, seed size, bag/tag germination records and planter maintenance is critical.
If you have questions about soybean seed quality, please reach out to your local Golden Harvest Seed Advisor or agronomist.
References:
Minimizing Mechanical Damage to Soybean Seed. 1984. Iowa State University Extension.
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