oilseed rape fertiliser and yield calculator
A tonne of oilseed rape removes about 30 kg of nitrogen, 14 kg of phosphate and 11 kg of potash from the field. Replacing offtake is the starting point for any nutrient plan.
- Phosphate product rate
- 121.7 kg/ha
- Potash product rate
- 73.3 kg/ha
- Nitrogen removed by the crop
- 120.0 kg N/ha
- Phosphate removed
- 56.0 kg P2O5/ha
- Potash removed
- 44.0 kg K2O/ha
- Nitrogen product for the whole area
- 19.876 tonnes
- Phosphate product total
- 4.870 tonnes
- Potash product total
- 2.933 tonnes
- Seed for the whole area
- 0.160 tonnes
- Expected harvest
- 160.0 tonnes
- Applied nitrogen per tonne of yield
- 42.86 kg/t
Show the working
- Area = 40
- Target yield = 4
- Nitrogen content of your product = 34.5
- Phosphate content = 46
- Potash content = 60
- Nutrient use efficiency = 70
- Seed rate = 4
- Expected harvest = 4 * 40 = 160
- Nitrogen removed by the crop = 4 * 30 = 120
- Phosphate removed = 4 * 14 = 56
- Potash removed = 4 * 11 = 44
- n_applied = 120 / (70/100) = 171.429
- Nitrogen product rate = 171.429 / (34.5/100) = 496.894
- Phosphate product rate = 56 / (46/100) = 121.739
- Potash product rate = 44 / (60/100) = 73.3333
- Nitrogen product for the whole area = 496.894 * 40 / 1000 = 19.8758
- Phosphate product total = 121.739 * 40 / 1000 = 4.869 57
- Potash product total = 73.3333 * 40 / 1000 = 2.933 33
- Seed for the whole area = 4 * 40 / 1000 = 0.16
- Applied nitrogen per tonne of yield = 4 > 0 ? 171.429 / 4 : 0 = 42.8571
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- nutrient removed = yield x removal rate per tonne
- product rate = nutrient required / nutrient content of the product
- nitrogen is adjusted for use efficiency because losses are unavoidable
Removal rates are typical published figures and vary with variety, season and whether the straw or residue is taken off.
This replaces what the crop takes. A proper plan also accounts for soil indices, manure history and any legume in the rotation.
Phosphate and potash build or deplete a soil reserve rather than being used in-season, so a below-index soil needs more than removal.
oilseed rape nutrient removal
| Nutrient | Per tonne of crop | At 4 t/ha |
|---|---|---|
| Nitrogen (N) | 30 kg | 120 kg/ha |
| Phosphate (P2O5) | 14 kg | 56 kg/ha |
| Potash (K2O) | 11 kg | 44 kg/ha |
Frequently asked
How much nitrogen does oilseed rape need?
It removes about 30 kg of N per tonne of crop, so a 4 t/ha crop takes off roughly 120 kg/ha. Applied rates are higher because not all of it is taken up.
Where the numbers come from
- Nutrient removal figures follow the usual published offtake tables; check against local recommendations.