Answers are from the Indiana certified crop adviser panel: Gene Flaningam, Flaningam Ag Consulting, Vincennes; Carl Joern, Pioneer, Lafayette; and Greg Kneubuhler, G&K Concepts, Fort Wayne.

 

I’m thinking about backing my soybean seeding rate off by about 10,000 to 20,000 to save on seed costs. I’m currently at 140,000 seeds per acre. Is this a wise move? How much can I cut?

 

Flaningam: Seeding rates need to be adjusted according to factors like planting date, soil productivity and variety standability. Earlier-planted soybeans favor a lower population. They tend to branch out more, having more nodes and pods per plant. Lighter soils will take a higher population to maximize productivity versus heavier soil types, which will support plant growth much better. I don’t think there is a magical number that fits every farm operation. Adjust your seeding rates according to your experience, and do some population tests on your own farms.

 

Joern: You can certainly achieve high-yielding soybeans at reduced seeding rates, but it ultimately comes down to your tolerance for risk. Lowering seeding rates can lead to increased weed competition, higher canopy temperatures due to greater soil exposure to solar radiation, and reduced buffer against stand losses caused by fungal pathogens, insect pests and environmental stressors like crusting, frost and ponding.

 

Consider some rough numbers. If you purchased soybean seed at $70 per unit, every 2,000 seeds per acre you cut saves you about $1. Is a $5- to $10-per-acre savings worth the potential risk of reducing your harvestable stand and, ultimately, your yield? At a fall delivery price of $10 per bushel, maintaining yield while reducing seeding rates is essential. Is this a risk worth taking, or is $5 to $10 per acre “cheap insurance” for a more reliable stand?

 

If you choose to reduce seeding rates, I recommend doing so in the middle of your planting window. Early-planted soybeans need a higher buffer since they face more adverse conditions and greater pest pressure. Conversely, late-planted soybean seeding rates should increase by 10% for each week that passes in June. Since late-planted soybeans have a shorter growing season and fewer opportunities to develop nodes, increasing seeding rates helps compensate for lost yield potential of individual plants.

 

Kneubuhler: Lower populations of soybeans can be very consistent in terms of yield. Of course, you need to factor in row spacing to truly answer this question. Are we talking 30-inch, 20-inch or 15-inch rows? That would drive the final decision.

 

Assuming we are talking about 15-inch soybeans, it’s not uncommon to find yield response curves at optimum rates under 140,000. When you start to shave seeding rates down, evenness across the field becomes very important. You don’t want areas of 150,000 and areas of 80,000 plants per acre.

 

Many of our trials over time have shown economic and agronomic populations in 15-inch rows to be around 125,000 seeds per acre. I like to also include the “insurance” factor rate when planting early, when you don’t know what Mother Nature will throw at you. Don’t lower rates so much that Mother Nature throws you a curve ball and you’re staring at a questionable stand that needs to be replanted. At an elementary level, make passes at lower rates to find how much you can comfortably cut.