The “sweet spot” of plant populations is where the yield increase from adding plants is just enough to pay for the seed needed to add them. Calculate how many seeds 1 extra bushel of yield will “buy,” says University of Illinois Agronomist Emerson Nafziger, At a seed cost of $3.75 per 1,000 seeds ($300 per 80,000-seed unit) and corn at $4.50 per bushel, one bushel of yield will buy 1,200 seeds. So adding that many plants would have to increase yield by 1 bushel per acre just to break even. That might not sound like a lot, but Nafziger’s data shows that if you’re already in the mid-30,000s for plant population, getting that is less likely than many believe.

Across 20 University of Illinois trials under dry conditions in recent years, yield leveled off at only about 32,000 plants per acre. Under lower-yielding conditions responses to population tended to flatten out at populations in the high 20,000s or low 30,000s. Under higher-yielding conditions there were some responses up to the low 40,000s.

Syngenta seeding rate study