Will Hybrid X yield more if planted thicker?

Corn Corner: Here’s an age-old question that’s worth another look.
Jan 01, 2019
I’ve been planting 32,000 seeds per acre. I really liked how a certain hybrid looked last year, and it yielded 210 bushels per acre — middle of my pack. My seedsman says it would do better planted at 35,000 to 36,000 seeds per acre. That would be a big jump in seeding rate. Should I do it?
The Indiana certified crop advisers panel answering this question includes Andy Like, Syngenta sales rep, Vincennes; Jeff Nagel, agronomist with Ceres Solutions LLP, Lafayette; and Darrell Shemwell, agronomist with Posey County Co-op, Poseyville.
Like: Yes, if you trust the opinion of your seedsman. The correct seeding rate can be affected by variables such as hybrid, planting date, weather and soil type, to name a few. So, getting advice from a local expert who has some experience with that hybrid has a lot of value.
Nagel: Deciding Hybrid X’s seeding rate is among many crop production decisions you must make.  Purdue University on-farm research suggests the agronomically optimum seeding rate for typical growing conditions and yield levels is around 33,000 plants per acre in 30-inch rows. Factor in seeding cost, and the economically optimum seeding rate would be lower.
Most seed companies today generate good data on response to population by hybrid. I would ask for research that supports the recommendation. Assuming a bag of corn costs $250 to $275, it would cost around $3 to $3.50 per thousand seeds for every extra 1,000 seeds. 
If you increased seeding rate to 35,000 seeds per acre, that would be another $9 to $10.50 per acre in seed costs. Does data support a yield increase over 2.5 to 3 bushels per acre for this increase to generate a positive return on investment?
Certainly, as seeding rates are increased, more stress can occur on plants, and some handle this better than others. Moisture-holding capacity of the soil, proper nutrition and plant health management needs to complement higher seeding rates.
Shemwell: This will depend on the individual hybrid and your personal yield goals and soil capability.  Some hybrids have flex-ear types, which will add length if conditions are right and don’t have to be planted at higher populations to achieve higher yields. Some hybrids have a determinate or semi-determinate ear type. These hybrids produce the same size ear at 30,000 seeds per acre or 34,000 seeds per acre. If you’re going to achieve higher yields with these hybrids, plant at higher populations. Since your seedsman is making this recommendation, ask for yield data to support it. 
I also mentioned personal yield goals. If you’re happy with 210 bushels per acre, that’s great. But if everyone around you averages 230 to 240 bushels per acre, you may want to see what they’re doing that you aren’t. 
If you were planting a determinate hybrid and increased population 1,000 seeds per acre and ended up with an 800-plant increase, producing an ear weighing 0.4 pound, this would theoretically be a 5.7-bushel increase. 
We know we just can’t keep increasing populations and get the same results. Other factors come into play. If you plant a hybrid that has a lot of ear-flex, you may not see any increase by raising your seeding rates. You need to trust your seedsman to make the best recommendation for you and your farm because every field and situation are different.