Seeding Rate & Plant for Profit, Not Yield
Optimises corn
More seed always adds a little more yield — but the last seeds cost more than the grain they make. This tool finds the plant population that maximises profit at today's seed and grain price, plots revenue against seed cost, and shows the dollars per acre you leave on the table off-optimum.
Enter your seed & grain economics
Next: your 35.8k rate is already at the profit peak for these prices — hold it, and re-check the optimum if seed or grain price shifts more than ~15%.
Mitscherlich diminishing-returns yield model fitted to ISU / Univ. of Nebraska / K-State population trials. The economic optimum is where the value of one more 1,000 seeds of grain equals the seed cost — it shifts down when seed gets dearer or grain cheaper. Planning figures; confirm with local trial data and a strip test.
Seeding-rate economics — key facts
- Optimum rule
- marginal grain value = seed cost
- Corn optimum
- ≈ 34,000 plants/ac established
- Soybean optimum
- ≈ 120,000 plants/ac
- Wheat optimum
- ≈ 1.3 million plants/ac
- Dearer seed
- → lower optimum population
- Dearer grain
- → higher optimum population
- Max yield
- is past the profit peak
- Privacy
- Runs in your browser; nothing uploaded
The most profitable rate is below the highest-yielding rate
Seeding rate is one of the few inputs a grower sets exactly, and it is easy to over-buy. Yield rises with population along a curve that flattens toward a plateau — each extra 1,000 seeds buys a little less grain than the last. The agronomic optimum (the population the trials recommend) maximises yield, but the economic optimum maximises profit, and it sits a notch lower: at the point where the value of the grain from one more 1,000 seeds exactly equals what those seeds cost.
This calculator plots three lines against population — revenue (rising and flattening), seed cost (a straight rising line), and net profit (their difference, a hump). The peak of the net line is the economic optimum, and it moves: cheaper seed or dearer grain pushes it up, dearer seed or cheaper grain pulls it down. Pair it with the Plant Population Yield Response, Seed Rate and Thousand-Grain-Weight tools to convert the optimum into kilograms of seed and a planter setting.
Agronomic-optimum populations by crop
| Crop | Optimum (plants/ac) | Typical seeding window | Plateau yield | Source |
|---|---|---|---|---|
| Corn (maize) | ~34,000 | 28,000–40,000 | ~280 bu/ac | ISU / Univ. of Nebraska population trials |
| Soybean | ~120,000 | 100,000–160,000 | ~75 bu/ac | Univ. of Nebraska / Iowa State seeding-rate trials |
| Winter wheat | ~1,300,000 | 900,000–1,800,000 | ~90 bu/ac | Kansas State / Univ. of Nebraska wheat studies |
Coefficients fitted so the profit optimum lands on the published agronomic optimum at typical prices. Sources: Iowa State University, University of Nebraska CropWatch, Kansas State University population trials. Planning figures — confirm locally.
How to find the profit-maximising rate
- 1Pick the crop. Choose corn, soybean or winter wheat to load its fitted yield-response curve.
- 2Enter your seeding rate. Type the rate you plan to plant, in thousands of seeds per acre.
- 3Enter today's prices. Set the grain price per bushel and the seed cost per 1,000 seeds.
- 4Set establishment. Enter the percent of seeds you expect to emerge — that converts the rate to a stand.
- 5Read the optimum. Read the economic optimum, your net return, and the dollars per acre you leave on the table; press Set to optimum to match it.
Frequently Asked Questions
What is the economically optimal seeding rate?+
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.
Why maximise profit instead of yield?+
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.
How does seed price change the optimum?+
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.
How does grain price change the optimum?+
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.
Is 36,000 corn population too high?+
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.
What is the formula for the economic optimum?+
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.
What is the marginal yield per 1,000 seeds?+
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.
What is the break-even population?+
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.
Does field establishment matter?+
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.
Which crops are supported and where do the curves come from?+
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.
Should I just plant the agronomic recommendation?+
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.
How accurate are the dollar figures?+
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.