Considerations for making carry-over soybean seed decisions
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EmailProducers want to salvage the soybean seed they carried over from 2019 but need to make this decision carefully.
Due to the continuously wet weather occurring in 2019, many soybean producers were not able to plant all their soybean acres and took the prevent plant option. Because of this and the fact that some seed companies would not allow producers to return treated seed, a large quantity of soybean seed has been stored on farms. A conservative estimate for Michigan is that 110,000 units were carried over. This would be enough seed to plant one-third of the prevent plant acres from 2019. Assuming an average price paid of $60 per unit, this represents a total investment of $6,600,000.
Producers want to recoup this investment by planting the carry-over seed in 2020. However, there is a high probability that the quality of the seed has declined in storage. Actual germination test results from this spring show that the quality of the carry-over seed is, in fact, significantly lower than that of the seed beans grown in 2019 (see table).
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Average germination test scores for carry-over soybean seed and new soybean seed grown in 2019. |
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Sample source |
Average warm germination (%) |
Average cold germination (%) |
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Carry-over seed from 2019 (44 lots) |
71.8 |
40.0 |
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New seed grown in 2019 (23 lots) |
96.9 |
91.3 |
Source: Michigan Crop Improvement Association
There are two factors that affected the quality of the carry-over seed. The first is that the seed quality in some seed lots sold in Michigan in 2019 was reduced to begin with. The second is that most of the seed was not stored in controlled atmosphere storage facilities at a constant 50 degrees Fahrenheit and 50% relative humidity.
As planting time approaches, producers need to make the best possible decisions about how to use this seed in their operations. The first step is to submit representative samples of all carry-over seed lots to the Michigan Crop Improvement Association for testing as soon as possible. When submitting samples, request the standard warm germination test and the cold test. Use the test results to make informed decisions.
The first decision is whether the carry-over seed should be planted. After reviewing some test results from this spring, I believe a reasonable guideline is to consider planting all seed lots having warm germination scores of 70% or above and cold germination scores above 50%. When I applied my guideline to 44 randomly selected carry-over seed lots tested this spring, only 18 of them should be planted if this method was used.
I discussed this guideline with agronomists and seed specialists and have received a wide range of feedback. Some feel that the cut-off should be a warm germination score of 80% to manage risk and others feel that seed lots having warm germination scores above 50% should be planted as too much value would be wasted otherwise. You will have to make this decision based on your tolerance for risk. Always follow the recommendations provided below when planting carry-over seed:
- Increase the planting rate to compensate for the lower germination scores.
- Always plant your highest quality seed lots first and plant the lower quality seed lots later and under more favorable soil conditions (a good seed bed with low residue cover).
- Handle the seed as infrequently and gently as possible.
- Do not attempt to retreat the carry-over seed as the additional handling increases the likelihood for further damage.
- Do not blend carry-over seed lots with new seed due to the additional handling required.
- Apply inoculant to the seed, when needed, in the gentlest way possible. The inoculant that was originally applied is no longer viable.
When adjusting planting rates, consider the soil and weather conditions at the time of planting. If soils are warm and moisture is adequate, use the warm germination test score to adjust rates. If less than ideal conditions exist at planting, use the cold germination score. The plants shown in the photo above have been subjected to the cold test. The plants that were slow to emerge have less seedling vigor and will never catch up.
Also, keep in mind that heavy rainfall after planting can cause a crust to form at the soil surface. Carry-over soybean seed will not have the energy to endure or emerge in these conditions.
In today’s challenging times, information is becoming increasingly important in making management decisions. When making decisions regarding carry-over soybean seed, please pay extra attention to germination test results this season.