Crop Yield Calculator

How the Crop Yield Calculator works

How many bushels. To see how many bushels per acre a sample represents, convert t/ha to kilograms per acre and divide by the bushel weight: 3 t/ha of wheat is 3,000 ÷ 2.471 ÷ 27.2 = 44.6 bushels per acre.

The whole season comes down to yield. Estimating it before the combine goes in helps you plan storage and haulage, decide how much to sell forward, and judge whether a new variety or fertiliser change paid off. The reliable way to estimate it is to harvest and weigh a known area. This calculator scales that sample up to the field and handles the unit conversions that follow.

Where yield estimates are used. Farmers sell grain forward months before harvest. A yield estimate that comes in 15 % too high can leave a contract short and force a purchase on the spot market to fill it. Crop insurers and government schemes such as the US Federal Crop Insurance programme settle claims on measured yield against a farm's history. Agronomists running strip trials compare the treated and untreated strips by yield, so an error of half a tonne can hide a real effect. Merchants and co-ops use estimates from across a district to book drying, storage and transport capacity.

Sampling. Mark out a plot with a quadrat or tape. One square metre is quick for grass and cereals, while ten square metres gives a better average. For potatoes the standard is to lift a measured length of row, where the area is the row length times the row spacing. Take several plots across the field, avoiding headlands and tramlines, and average them. A single square metre in a good patch can overstate the field by 20 % or more. Weigh grain after threshing, tubers after knocking off the soil, and grass fresh as cut.

The formula. Yield in tonnes per hectare = sample weight in kg ÷ plot area in m² × 10. For example, 8 kg from a 10 m² plot is 0.8 kg/m², which is 8 t/ha. An acre is 0.4047 ha, so divide t/ha by 2.471 to get tonnes per acre. Bushels are a volume measure with a standard weight for each crop: 60 lb (27.2 kg) for wheat and soybeans, 56 lb (25.4 kg) for maize, 48 lb (21.8 kg) for barley, 32 lb (14.5 kg) for oats and 50 lb (22.7 kg) for canola. The calculator uses these to report bushels per acre for grain crops.

Moisture. Grain is traded at a standard moisture: 15 % for wheat and barley, 15.5 % for maize, 13 % for soybeans and 9 % for oilseed rape. Grain cut at 20 % moisture weighs more than the same grain dried to 15 %, so a yield estimated from wet grain is inflated. Enter the moisture at harvest and the calculator scales the dry matter to the standard:

yield at standard = yield × (100 − harvest moisture) ÷ (100 − standard moisture).

For example, 9 t/ha of wheat at 20 % becomes 9 × 80 ÷ 85 = 8.47 t/ha at 15 %. Leave the field blank for potatoes and grass, which are sold fresh.

Typical yields. UK wheat averages around 8 t/ha, and the best fields top 11. Barley gives 6–7, oats 5–6, and grain maize 9–10 where it is grown. Soybeans average about 3 t/ha in the US Midwest, oilseed rape 3.5, maincrop potatoes 40–50 t/ha fresh, and a good silage cut 25–35 t/ha fresh. Climate makes a large difference: Australian wheat averages nearer 2 t/ha, while Irish wheat averages over 9.

Reading the crop yield calculator result

• Yield as harvested is the sample scaled to a hectare and an acre, with no moisture correction. For grass and potatoes this is the figure that matters.
• Yield at standard moisture is what a merchant would pay on. If it is much lower than the as-harvested figure, drying costs will be high as well.
• Bushels per acre appears for grain crops so you can compare with US and Canadian figures, or with futures prices quoted per bushel.
• Total multiplies the corrected yield by the field area. Use this line to plan trailers, drying time and bin space.
• Against a typical yield gives your estimate as a percentage of the benchmark above. Treat anything under 60 % or over 140 % as a reason to re-check the sample before relying on it.

Tips and pitfalls. Sample after the crop is fully ripe; grain filling can still add 10 % in the last fortnight. Take at least five plots in a W pattern across the field rather than walking in from the gate. Knock the soil off potatoes and remove any stones before weighing, or the result will look implausibly high. Measure the plot accurately: a quadrat that is 5 cm short on each side of a square metre is really 0.9 m², which is a 10 % error before you even start. Headland losses, lodged patches and combine losses mean the weighbridge usually comes in 5–10 % below a careful hand sample.

Using the field total. A 10 ha field at 8 t/ha is 80 tonnes. That is about five articulated lorry loads, or two and a half days in a small batch drier. If you need the area from the field's dimensions, use the field area calculator.

Wheat yield from a 10 m² sample

Grain cut from a 10 m² plot, scaled up to a hectare and an acre.

Wheat yield per hectare and bushels per acre by 10 m² sample

Sources: Crop yield.

Checked against: Yield = harvested quantity ÷ area harvested

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