You've read a lot about the difference in optimum nitrogen rates to maximize yields and the optimum nitrogen rate to maximize economic profit. That's because nitrogen has always been one of the leading input costs for corn. It's also because at some point the curve of nitrogen response for the next pound of N added levels out, and typically even tops out and begins to decline slightly at very high rates.

Corn Illustrated 12/8: UAVs bring corn nitrogen trials to life

This year the economic crunch is so tight that both corn specialists and ag economists are shining a light on seed costs, suggesting that you may want to consider if you could shave seed costs while giving up very little if any yield.

The theory is similar. Bob Nielsen, Purdue University Extension corn specialist, says that in their trials, many of them large-scale field trials and some on-farm trials as well, yield response to population flattens out in the high 20,000 to low 30,000 range of plants per acre for final stand. Purdue's current recommendation for maximum yield is a final stand of 32,000 plants per acre, or a seeding rate of roughly 34,000 seeds per acre.

Converted to seeding rate, it flattens out at about 29,000 to 34,000 seeds per acre. His work indicates only a one to two bushel yield dip for the lower population over that range. He's again talking economic maximum vs. agronomic top yield.

Here's how his math looks. If you pay $3.00 per 1,000 seeds, and that's corn priced at $240 per bag, which might be a bargain, then seed costs per acre range from $87 to $102 per acre for 29,000 vs. 34,000 seeds per acre.

Suppose you give up 2 bushels per acre at $3.50 per bushel. That's a loss of $7 in revenue for $15 less expense. You net $8 per acre more. On 1,000 acres, that's $8,000 higher net return.

Corn Illustrated 12/1: Soil test activity slows across the Corn Belt

The kicker, of course, is whether the yield curve is actually as flat as Purdue's data indicates. Some seed companies might agree, others would not. Some would say it depends upon the hybrid. Still others say it depends upon the hybrid and row spacing, and would indicate that at narrowing spacing, there is opportunity to up yields at higher populations.

The economic optimum seeding rate theory also doesn't account for how much stand risk you're willing to take. How much do you factor in per acre as a cost for risking planting at the low end, 29,000 seeds per acre, and only achieving 24,000 due to stand establishment issues? In other words if you opt to trim costs, you reduce your margin for error in obtaining good stands.