Seed Quality and Planting Populations in Soybeans

The two most discussed topics on the meeting circuit this winter were “Plant Your Soybeans Early” and “Lower Your Planting Population.” Both are great recommendations in a time when dollars are tight. Planting early is a management practice that doesn’t cost a grower anything and lowering your seeding population can save you money.

More and more data is being collected and presented showing that soybeans can still reach the upper 90th percentile of yield potential with populations as low as 90,000 seeds per acre. For many growers lowering seeding rates is a gradual process. Lowering rates 5,000 – 6,000 seeds per acre, per year and finding a comfortable population for a particular soil type may take some trials.

Components of Seed Quality
This year many seed companies are struggling with seed quality. In much of the Midwest dry conditions from late May to late August contributed to poor seed quality. Much of the problem is due to thin seed coats with high potential for mechanical damage. Another factor contributing to poor seed quality is the extremely warm stretch of weather in late September when many were harvesting soybeans. After a cool August and early September a stretch of almost 2 weeks of 90-degree heat really helped the corn crop mature, but sucked the moisture from the maturing soybean crop too fast. Many growers were left harvesting sub 10 percent soybeans, and in some extreme cases 8 percent moisture.

A repeated wet and dry cycle that doesn’t allow for timely harvest can also cause quality issues. As the seed takes in moisture then dries, the seed coat can become wrinkled or cracked. I have seen the seed coat come completely off in some lots during the seed treatment process. Once the treatment is applied and the dye is on the seed it is also more obvious to see the wrinkles in the seed coat.

Picking the Perfect Plant Population
When calculating the desired final stand on soybeans, the germination percentage should be taken into consideration. Some lots will be tagged at 85 percent or even 80 percent. This needs to be factored in when calculating for stand. The University of Illinois has a handy calculator for population considerations.

Know what the germ is on your soybean lots and make a decision on planting population based on the information you know. You may choose to seek additional information, such as a vigor test or warm germination score. This information will help growers make a more accurate planting population plan. Remember, seed treatments can protect the seed and its’ current quality, but they cannot improve the quality.

Ehler is a sales agronomist for Ehler Brothers Co. in Thomasboro, Illinois. He is a graduate of the University of Illinois, Champaign-Urbana and has been a Certified Crop Adviser for 15 years. He was the first Illinois Soybean Association Master Soybean Adviser winner in 2017. Ehler was part of the advisory and agronomy team to help growers Bob and Jason Lakey set the Illinois state soybean record of 108 bu/A in 2015. His social media page, The Pursuit of 100+ Bushel Soybeans, has helped growers confidently implement early planting and management practices to increase yields.