Winter Oilseed Rape
Nitrogen, Phosphour and Potassium
Nitrogen, P and K advice for oil seed rape is shown in Table 1. The first split of N should be applied in late February and the remainder in the first week of April. The first split should be about 30% of the total. It is unlikely that the application of N at sowing time is justified, but if it is used, it should not exceed 40 kg/ha of N. fertiliser applications should not be combined drilled as this may delay germination.
The pH for oil seed rape should be above 6.5.
N, P & K for Winter Oilseed Rape (Kg/ha) | |||
---|---|---|---|
Soil N, P & K Index | N | P | K* |
1 | 225 | 55 | 105 |
2 | 180 | 45 | 90 |
3 | 160 | 35 | 75 |
4 | 140 | None | None |
*K advice based on 5t/ha |
Sulphur
Oil seed rape responds to the application of S on sandy soils. A dressing of 25 kg/ha S should be adequate.
Magnesium
If the soil Mg is Index 1, apply a source of Mg. Use magnesium limestone if the pH is low or 75 kg/ha of calcined magnesite or kieserite every three years.
Boron
Boron should be applied for oil seed rape especially when the soil test is below 1 mg/l. Severe B deficiency causes stunting and brittle petioles, but relatively mild deficiency results in poor seed set and a reduction in seed numbers per pod and seed weight. These conditions can be induced by severe summer drought.
A spray at sowing and in the spring should prevent the occurrence of B deficiency.
Phosphorus (P) and Potassium (K) Removals for Oilseed Rape
The majority of P and K is removed in the seed at harvest time (6.0kg P /tonne & 9.1 kg K /tonne). The straw contains small amounts of both P and K (0.44kg P /tonne & 5.0 kg K /tonne).
The table below shows the P and K removed in seed and straw based on crop yield (t/ha) and the total removal of P and K by the crop.
Nutrients in Oilseed Rape (seed & straw)* | ||||
---|---|---|---|---|
Crop Yield (t/ha) | 2 | 3 | 4 | 5 |
Seed Only | ||||
P | 12 | 18 | 24 | 30 |
K | 18 | 27 | 36 | 46 |
Straw Only | ||||
P | 0.9 | 1.3 | 1.8 | 2.2 |
K | 10 | 15 | 20 | 25 |
Total P & K Removal in Seed and Straw | ||||
P | 12.9 | 19.3 | 25.8 | 32.2 |
K | 28 | 42 | 56 | 71 |
* Take note the figures in the above table do not take account of additional P and K required to build soil fertility at low soil indexes (Index 1 or 2). Consult the Teagasc Green Book for additional P & K for building soil fertility to the optimum soil index 3.