The quality of the soybean seed we are about to plant in the coming weeks is outstanding, in sharp contrast to the quality of the seed we planted in 2008. Poor germination and vigor for a lot of seed last year resulted in a significant amount of seed withheld or removed from the seed sale pipeline.
This, coupled with extreme demand due to high soybean prices, resulted in a shortage of good quality seed to be planted last year for many varieties. Or so we thought. A common theme last year was, “We planted nine seed per foot of row and we got 12 up.”
Seed size last year as a whole was extremely small. Seed size varies from variety to variety due to genetics and from year to year due to the environmental conditions in seed production fields. Soybean seed size can vary from less than 2,000 seed per pound for large-seeded varieties to greater than 4,000 seed for small-seeded varieties.
Seed size, averaged across all varieties, is typically around 2,900 seeds per pound. Last year average seed size was around 3,400 seeds per pound.
Extremely small seed size last year resulted in planters dropping a lot of doubles (i.e. dropping two seeds rather than one) because planter plate cells picked up two seeds rather than one.
This resulted in some higher-than-desired plant populations and, coupled with later-than-desired planting, some lodging in fields. Late planting in late April through early May can result in excessive growth and lodging potential, especially under irrigated conditions and when planting on silt loam or light textured soils.
Seed shortages last year also resulted in planting more seed than desired in a lot of cases due to the risks of stand failures and knowing there was very little seed available for replanting.
The above-mentioned scenarios — poor quality seed, seed shortages, and small seed — will not be the case for this year’s soybean crop. Following is a rundown of the test results for the soybean seed tested by Fabian Watts and his team in the Mississippi Department of Agriculture seed testing lab in Starkville, Ark. These results are for seed we will be planting in the coming weeks.
• 96 percent of soybean seed tested had at least 80 percent germination, compared to only 60 percent last year.
• 77 percent of this year’s seed tested greater than 90 percent germination, compared to only 38 percent last year.
• Only 1 percent of seed for this year’s crop tested below 80 percent germination, compared to 40 percent last year.
• Averaged across all tested seed, the average germination for this year’s seed is 91 percent, compared to 76 percent last year. Overall, germination levels for seed to be planted in this year’s crop is excellent and at near record levels.
• The overall vigor of this year’s seed is excellent and much better compared to last year.
Soybean seed vigor is often measured using the accelerated aging test. Soybean seed is exposed to extreme temperature and humidity regimes in this test according to standard procedures developed by the International Seed Testing Association.
The extreme temperature and humidity regime results in rapid deterioration of the poor quality seed. After exposure to the accelerated aging test, the percent germination for the seed is determined using standard germination procedures. Better seed vigor results in a higher percentage of the seed that germinates and establishes into a seedling.
Seed having good vigor will have similar germination levels after exposure as germination levels for seed not exposed to the accelerated aging test. If germination levels fall off significantly after the seed is exposed to the accelerated aging test, compared to germination levels for seed not exposed to accelerated aging test, this is a good sign that the overall seed vigor is poor.
There is no standard accepted germination level for soybean seed exposed to the accelerated aging test. However, accelerated aging levels below 65 percent are often deemed unacceptable.
• 53 percent of this year’s seed tested better than 90 percent germination after exposure to the accelerated aging test. This compares to 15 percent of last year’s seed.
• 95 percent of this year’s seed tested at least 60 percent germination after the accelerated aging test, compared to 79 percent of last year’s.
Overall, the quality (germination and vigor) of the seed for this year’s crop is excellent, and we have to go back many years to find testing levels of this quality.
There are several things to keep in mind about the outstanding seed quality characteristics of the seed we are about to plant.
• Unlike last year, we want to mindful of seeding rates when planting this year’s crop.
• Unlike last year, there is no need to deviate from recommended seeding rates. The tables found at Soybean seed guidelines provide recommended plant populations and seeding rates for various row patterns according to maturity group, soil type, and planting date for Mississippi soybean producers.
Excessive seeding rates can result in unwarranted cost, lodging, as well as significant yield reductions under some environmental conditions. Planting late Group 4s and early Group 5s at higher than recommended seeding rates in 38- or 40-wide row patterns can decrease yields by as much as 15 percent.
In addition to the obvious benefits of planting good quality seed, I hope the results of planting quality seed will be seen this fall with an excellent yielding soybean crop for all Mid-South soybean producers.