Seeding Rate & Plant for Profit, Not Yield

It is the plant population where the value of the grain from one more 1,000 seeds just equals the cost of those seeds. Plant fewer and you give up grain worth more than the seed; plant more and the extra seed costs more than the grain it adds. The tool solves this analytically from a diminishing-returns yield curve and your prices — for corn it is usually around 34,000 plants per acre established.

Yield keeps creeping up as you add seed, but it does so by smaller and smaller amounts — that is the diminishing-returns curve. The highest-yielding population is almost always a few thousand seeds above the profit peak, where the last seeds cost more than the grain they produce. Chasing maximum yield therefore quietly burns money on every one of those last seeds.

Higher seed cost lowers the optimum population, because each extra 1,000 seeds must clear a higher bar of grain value to pay for itself. Cheaper seed raises the optimum. The tool re-solves the optimum live as you change the seed cost per 1,000 seeds, so you can see the population move.

Higher grain price raises the optimum population — when each bushel is worth more, the marginal grain from extra seed clears the seed cost more easily, so it pays to plant a little heavier. Lower grain price pushes the optimum down. This is why the profit-maximising rate is not a fixed agronomic number but a moving economic target.

It depends on your prices. At typical corn economics the profit optimum sits near 34,000 established plants per acre, so 36,000 is slightly past the peak and usually loses a few dollars per acre on the last seed. With very cheap seed or high grain price the optimum can rise above 36,000; the tool shows exactly where your peak is for your numbers.

Using a Mitscherlich yield model Y(p) = Ymax·(1 − e^(−k(p−p0))), the marginal grain per extra plant is Ymax·k·e^(−k(p−p0)). Setting its value equal to the per-plant seed cost and solving gives p* = p0 + (1/k)·ln(Ymax·k·grainPrice ÷ seedCost). That is the population at which marginal grain value equals marginal seed cost.

It is how many extra bushels per acre you gain by planting one more 1,000 seeds at your current rate. It is large at low populations and shrinks toward zero as you approach the plateau. When that marginal grain is worth exactly the cost of the 1,000 seeds, you are at the economic optimum — add more and the marginal grain is worth less than the seed.

It is the population at which the grain value just covers the cumulative seed cost — below it you are not even paying for your seed. It sits well below the profit optimum: between the break-even and the optimum, each extra seed still adds more grain value than it costs. The tool reports both so you can see your profitable window.

Yes — you plant seeds but you harvest established plants. If only 90% of seeds emerge, your established population is 90% of the seeding rate, and the seed cost per established plant rises accordingly. The tool converts your seeding rate to an established population using the establishment percent and prices seed on a per-established-plant basis.

Corn, soybean and winter wheat. The yield-response coefficients are fitted so the profit optimum lands on the published agronomic optimum population at typical prices — corn near 34,000/ac, soybean near 120,000/ac, wheat near 1.3 million/ac established — drawn from Iowa State, University of Nebraska and Kansas State population trials.

The agronomic recommendation is a good starting point, but it assumes average prices. When seed is expensive or grain is cheap, the profit optimum drops below the agronomic rate; when the reverse is true it climbs above it. This tool adjusts the recommendation to your actual seed and grain prices so you plant for profit, not for an average season.

They are solid planning figures from your inputs and published response curves. Real fields vary with soil, hybrid, planting date and weather, so treat the optimum as a target to test, not a guarantee. Run a few strip trials at and around the optimum, and re-check the calculator whenever seed or grain prices move materially.