By Jeff Nagel
The evidence continues to mount. University researchers who aren’t even studying soybean seeding rates are reporting excellent yields at low rates — sometimes well below 100,000 seeds per acre.
You may not want to trim rates that far. Most research suggests soybeans achieve near maximum yields with harvest populations, not seeding rates, around 100,000 to 125,000 plants per acre. That will mean somewhat higher seeding rates.
You need to make sure your planter is equipped to achieve good seed placement and seed-to-soil contact if you’re trimming seeding rates. What other factors should you consider?
Here are six things besides the planter that could affect whether lower soybean seeding rates are successful.
1. Field characteristics and soil types. Higher seeding rates will likely be needed on lower organic matter timber soils with drainage concerns than reasonably well-drained fields with 3% to 5% organic matter. People who use variable-rate seeding prescriptions for soybeans typically increase rates on rolling soils and drop them on lower soils in the field.
2. Tillage system. Seeding rates can be lowered on fields that have less residue, and may need to be increased in conservation-tillage systems and when planting into cover crops. Planter modifications are more likely to be needed in no-till systems, so you can adequately handle the residue and still get seed placed uniformly and at an even depth. Covering the seed trench is critical.
3. Planting date. Planting early may carry more emergence risk. But when followed by warm stretches, early planting has resulted in very favorable emergence. The key is to assess soil temperature and the projected weather forecast before you plant. Perform adjustments as necessary.
4. Soybean variety. Check with your seed specialist on variety characteristics. Is the variety short and needs higher rates to perform best? Or is it taller so it might lodge at higher populations? If so, populations may need to be managed on the lower side. Is white mold a concern? Thicker stands and dense canopy tend to favor white mold where it is a concern.
5. Seed treatments. Most farmers use a seed treatment to help with stand establishment and early-season growth. However, not all seed treatments are alike. It’s good to know more than just “I have a fungicide and/or insecticide seed treatment.” You should know what active ingredients you are buying, what rates are recommended and what pathogens and/or insects the seed treatment targets.
6. Weed control. Never underestimate the value of a good early and seasonlong crop canopy for weed control. Higher populations may be desirable for control of weeds that can germinate all season long, such as Palmer amaranth and tall waterhemp.
Nagel is an agronomist with Ceres Solutions Cooperative. Tom J. Bechman contributed to this story.