How Many Seeds to Sow for Your Target Stand

How Many Seeds to Sow for Your Target Stand

How many seeds to sow for your target stand comes down to two numbers, the plants you want and the emergence you expect. The plant count is the target stand. The seed count is always larger, because not every seed becomes a plant.

Why the target stand is not the seed count

A target stand counts plants, not seeds. Some seeds fail to germinate. Some seedlings fail to establish after they emerge. Some seeds are lost to gaps, to doubles, and to the unevenness of a real field.

If you order exactly the plant count in seeds, the stand will fall short. At 90 percent emergence, 100 seeds give 90 plants. At 75 percent, 100 seeds give 75 plants. The Plant Population Calculator works this step in one move.

The core rule in one line

Seeds equal plants divided by emergence as a decimal. Emergence is a single combined figure that already covers germination and field establishment losses together. Do not add a second figure for germination or for field loss.

To turn a percent into a decimal, divide by 100. Emergence of 90 percent is 0.90, of 85 percent is 0.85, of 95 percent is 0.95, of 80 percent is 0.80, and of 75 percent is 0.75. Then divide the plant count by that decimal. Always round seed counts up, since a seed cannot be split and rounding down leaves the stand short. A result of 974.66 seeds means sow 975 seeds. Round up at the end, after the division, not before it.

How much extra seed each emergence level needs

The table shows the extra seed needed above the plant count at five emergence levels. At 95 percent you need 5.26 percent extra. At 90 percent you need 11.11 percent extra. At 85 percent you need 17.65 percent extra. At 80 percent you need 25 percent extra. At 75 percent you need 33.33 percent extra. Extra seed equals 1 divided by emergence as a decimal, minus 1, times 100. At 90 percent, 1 divided by 0.90 is 1.1111, minus 1 is 0.1111, times 100 is 11.11 percent.

Emergence	Decimal	Extra seed above plant count
95 percent	0.95	5.26 percent
90 percent	0.90	11.11 percent
85 percent	0.85	17.65 percent
80 percent	0.80	25 percent
75 percent	0.75	33.33 percent

Worked example 1: 10 hectares at 87,719 plants per hectare

Metric example from the calculator page. Rows 76 cm apart with plants every 15 cm give 8.77 plants per sq m, about 87,700 per hectare, or 87,719 exactly. The field is 10 hectares, so total plants equal 87,719 times 10, which equals 877,190 plants.

At 90 percent emergence, 877,190 divided by 0.90 equals 974,656 seeds. At 85 percent, 877,190 divided by 0.85 equals 1,031,988 seeds. At 95 percent, 877,190 divided by 0.95 equals 923,358 seeds. The 85 percent result is 108,630 seeds higher than the 95 percent result, and a five point fall from 90 percent to 85 percent adds 57,332 seeds.

Worked example 2: 50 acres at 34,848 plants per acre

Imperial example from the calculator page. Rows 30 in apart with plants every 6 in give 34,848 plants per acre. The field is 50 acres, so total plants equal 34,848 times 50, which equals 1,742,400 plants. This is a separate example from the metric example above. The metric spacing of 76 cm by 15 cm is not the same as 30 in by 6 in. In fact 76 cm is 29.92 in and 15 cm is 5.91 in.

At 90 percent emergence, 1,742,400 divided by 0.90 equals 1,936,000 seeds. At 85 percent, 1,742,400 divided by 0.85 equals 2,049,882 seeds. At 95 percent, 1,742,400 divided by 0.95 equals 1,834,105 seeds. The 85 percent result is 215,777 seeds higher than the 95 percent result.

Worked example 3: a small trial of 100 sq m

A small trial uses the same rule as a whole field. The trial area is 100 sq m. The density is 8.77 plants per sq m, the same density as the metric example above. Total plants equal 8.7719 times 100, which equals 877.19 plants, called 877 plants. The seed division uses the unrounded plant count.

At 90 percent emergence, 877.19 divided by 0.90 equals 974.66, so sow 975 seeds. Sowing 974 seeds gives only 876.6 plants, below the target of 877. Sowing 975 seeds gives 877.5 plants, just above the target.

A corn field example: 100 acres at 32,167 plants per acre

This example uses 32,167 plants per acre, from 30 in rows with 6.5 in spacing in the row. The field is 100 acres, so total plants equal 32,167 times 100, which equals 3,216,700 plants.

At 90 percent emergence, 3,216,700 divided by 0.90 equals 3,574,111 seeds. At 85 percent, 3,216,700 divided by 0.85 equals 3,784,353 seeds. At 95 percent, 3,216,700 divided by 0.95 equals 3,386,000 seeds. The 85 percent result is 398,353 seeds higher than the 95 percent result.

A small check from AgriFarming

A small check from AgriFarming uses the same rule at garden scale. The target is 500 plants. The germination figure used in that check is 85 percent. That is 500 divided by 0.85, which equals 588.2 seeds, rounded up to 589 seeds. Sowing 588 seeds gives only 499.8 plants, below the target of 500. Sowing 589 seeds gives 500.65 plants, just above the target.

This check is named as from AgriFarming because the 85 percent figure is a germination figure from that source, not from the calculator page, which gives a single emergence figure that you enter.

Warning: do not count the same loss twice

NovaCalculator gives a two factor method, seeding rate equal to target population divided by germination rate times field emergence. The example on that page is 34,000 divided by (0.95 times 0.95), which equals 37,674 seeds per acre. The two factors multiply to 0.9025, and 34,000 divided by 0.9025 equals 37,673.7, shown as 37,674 seeds per acre.

That arithmetic is correct, but it must NOT be combined with the Plant Calculator single emergence figure. Use the calculator single figure, or use the two factor method, never both, or the same loss is counted twice. The calculator single emergence figure already covers germination and field establishment losses together.

Take a target of 34,000 plants per acre. The single figure method at 90 percent emergence gives 34,000 divided by 0.90, which equals 37,778 seeds per acre. Now combine them by mistake. Divide 34,000 by 0.95 for germination, then divide the result by 0.90 for emergence. The result is 39,766 seeds per acre, about 2,000 seeds per acre too many. Choose one method and use it alone.

What the calculator does not give

The calculator gives seed count only, from the plant count and the emergence figure you enter. It gives no seed weight, no bag count, no seed cost, no seeds per pound figure, no yield, and no fertiliser rate. It also gives no replant decision and no stand count from a field sample. Do not invent any of those figures. Work weight, bags, and cost from your seed supplier figures.

Assumptions behind the seed count

The calculator assumes even spacing. Gaps and doubles change the real stand. Optimum populations depend on crop, variety and conditions. The calculator does not set an optimum population for your crop. Edge rows and headlands are included, so work the planted area only if a large headland will not be planted.

Common mistakes to avoid

First, do not order the plant count in seeds. The seed count is the plant count divided by emergence. Ordering the plant count leaves the stand 10 percent short at 90 percent emergence and 15 percent short at 85 percent emergence.

Second, do not count the same loss twice. Use the calculator single figure, or the two factor method, never both.

Third, do not round down. Always round seed counts up, so 974.66 becomes 975, not 974.

Fourth, do not mix units inside one sum. A plant count per hectare times hectares, or per acre times acres, gives total plants.

Fifth, do not treat the two page examples as the same spacing. Rows 76 cm apart with plants every 15 cm give 87,719 plants per hectare. Rows 30 in apart with plants every 6 in give 34,848 plants per acre.

Sixth, do not state a germination figure as if it came from the calculator page. If you use one from another source, name that source.

How to use your seed count when you order

Write the seed count down with the plant count and the emergence figure beside it. A line that says 877,190 plants at 90 percent emergence needs 974,656 seeds shows the target and the method used.

For a field scale order, work the seed count at two emergence levels, the emergence you expect and five points lower.

For a small trial, sow the rounded up seed count exactly, and count the stand after emergence. The trial gives a real emergence figure for your seed, your soil, and your planter.

The Seed Calculator works seed needs for starting seeds. The Plant Spacing Calculator works how many plants fit a bed from spacing. The guide on how many vegetable plants per person gives plant numbers by appetite. The Garden Area Calculator works out area from shapes.

Summary of the worked examples

Worked example	Area	Plants	Seeds at 90 percent	Seeds at 85 percent	Seeds at 95 percent
1, metric field	10 hectares	877,190	974,656	1,031,988	923,358
2, imperial field	50 acres	1,742,400	1,936,000	2,049,882	1,834,105
3, small trial	100 sq m	877	975	Not worked	Not worked
Corn field	100 acres	3,216,700	3,574,111	3,784,353	3,386,000

The summary table repeats the worked results in one place.

Frequently Asked Questions

Q: How many seeds to sow for a target stand?

A: Divide the target plant count by emergence as a decimal. At 90 percent emergence, 877,190 plants need 974,656 seeds.

Q: What is emergence in the seed count?

A: Emergence is one combined figure covering germination and field establishment losses together. Enter one figure and divide by it only.

Q: Why do I need more seeds than plants?

A: Not every seed becomes a plant. At 90 percent emergence you need 11.11 percent extra seed, and at 85 percent you need 17.65 percent extra.

Q: Should I round a seed count up or down?

A: Always round seed counts up, since a seed cannot be split. A result of 974.66 seeds means sow 975 seeds.

Q: Can I use a germination rate and the calculator emergence figure together?

A: No. Use the calculator single figure, or use the two factor method, never both, or the same loss is counted twice.

Q: What does the Plant Population Calculator give for seed?

A: It gives seed count only, from the plant count and the emergence figure you enter. It gives no seed weight, no bag count, no seed cost, no yield, and no fertiliser rate.