Yield calculator
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ha
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Yield as harvested
Yield at base moisture
A worked example is filled in. Use the base moisture set for your crop and buyer.
In short
Crop yield is harvested grain divided by harvested area, in tonnes per hectare.
Before harvest you estimate it from counts: heads per square metre times grains per head times grain weight, which gives a biological yield, an estimate of potential. After harvest the weighed yield differs from it by the harvest losses and by the sampling error. Planva records the season result for each field next to crop and variety, so both figures can sit side by side.
Units: t/ha, c/ha and g per square metre
| Unit | Equals | Use |
|---|---|---|
| 1 t/ha | 1,000 kg/ha, or 100 g per square metre | Most national statistics |
| 1 c/ha (centner) | 100 kg/ha, or 10 g per square metre | Common in farm reports |
| 10 c/ha | 1 t/ha | The conversion to remember |
The component formula
Extension services in Alberta and Texas estimate cereal yield from three components: heads per unit of area, grains per head, and grain size. In metric units the arithmetic is short. Heads per square metre times grains per head times the weight of 1,000 grains in grams, divided by 100,000, gives tonnes per hectare.
Yield (t/ha) = heads per m2 x grains per head x 1000-grain weight (g) / 100,000. With 400 heads, 35 grains and 40 g that is 400 x 35 x 40 / 100,000 = 5.6 t/ha. Alberta Agriculture labels its own version an estimate of potential yield, not harvested yield. Texas A&M adds that grain size is not settled until after flowering and depends on moisture, disease and variety.
The calculator below works from the scale, not from counts. It takes weighed grain, harvested area and moisture, and returns t/ha and c/ha at your base moisture.
Biological yield against harvested yield
The terms vary between farms, so write down in your report what each figure means. This guide uses two.
- Biological yield. Calculated from counts on sample plots just before harvest. It does not know what the combine will lose.
- Harvested yield. Weighed grain from the combine bin or at the weigh bridge, divided by harvested hectares, then corrected to the base moisture.
The harvested figure is the one that sells, and the biological figure is the one that explains it. A large gap between them has two parts. One is real harvest loss: grain shed before the header, lost at the header, or carried out the back of the machine. The other is sample error, because a few plots rarely match a whole field. Do not put all of the gap on the combine.
A worked example
| Step | Illustrative value |
|---|---|
| Heads per square metre | 400 |
| Grains per head | 35 |
| 1000-grain weight | 40 g |
| Biological yield | 5.6 t/ha |
| Weighed yield at harvest moisture of 18 per cent | 5.1 t/ha |
| Weighed yield at a base moisture of 14 per cent | 4.9 t/ha |
| Gap against the biological figure | 0.7 t/ha |
These numbers are an invented sample, not a field result. The moisture step uses the dry-matter rule: weighed yield x (100 - W) / (100 - W base), here 5.1 x 82 / 86 = 4.9. Your buyer or the national grain standard sets the base. The 14 is only an example.
Taking the sample
- Spread the points. A field practice guide from Kazan Federal University takes plants from sample squares placed at different places in the field and merges them.
- Count what the formula needs. Heads or stems with a head, and grains per head from a run of heads, not from one.
- Weigh the grain. Take the 1000-grain weight from a counted sample, or use your own seed record.
- Check the area. Divide harvested weight by harvested hectares, not by sown or field hectares.
How this works in Planva
- Season result. Crop rotation holds each season with crop, variety, sowing and harvest dates, yield and total harvest.
- Seed record. The seed catalogue holds germination, 1000-seed weight, maturity group and purity for each seed record.
- Area check. A machine task shows full, net and confirmed area from the track, which is one way to check the hectares you divide by.
- What it does not do. Planva records the result. It does not recommend rates or tell you which figure to believe.
For the level to expect, see wheat yield by country and corn yield. To keep the result against the field, start from the field history guide.
Sources
Common questions
Divide harvested weight by harvested area to get t/ha. Before harvest, multiply heads per square metre by grains per head and by 1000-grain weight in grams, then divide by 100,000.
The real Planva interface, shown with test data.
