ARCHIVE: Fertiliser Manual (RB209)

Oilseed rape, Autumn and Winter Sown – Nitrogen


  SNS Index
  0 1 2 3 4 5 6
  kg N/ha
Autumn 30 30 30 0 0 0 0
Spring
All mineral soils 220 190 160 120 80 40-80 0-40
Organic soils       120 80 40-80 0-40
Peaty soils           40-80

Timing of application

Autumn nitrogen can be applied to the seedbed or as a top-dressing to encourage autumn growth but research suggests that crops sown after early September are unlikely to respond.

Where the nitrogen rate is less than 100 kg N/ha, apply the whole dressing during late February-early March at the start of spring growth.

For amounts of 100 kg N/ha or greater, split the dressing with half at this time and the remainder by late March-early April.

Yield variation

The recommendations are for crops yielding 3.5 t/ha. Where previous experience of growing the crop indicates that yields above 3.5 t/ha can be expected realistically, the recommended rate may be increased by up to 30 kg N/ha per half tonne of yield up to an expected yield of 4.5 t/ha. This adjustment should be used with caution because applying too much early nitrogen to crops with large canopies can increase lodging and possibly reduce yield.

The effect of economic changes on nitrogen rates

The recommendations in the table are based on a breakeven ratio of 2.5 (see page 32). If the price of nitrogen or the value of grain changes, use the table below to decide on an amount to add or subtract from the nitrogen application.

Don’t forget to deduct nutrients applied as organic manures (see section 2)

  Fertiliser N content (%) Fertiliser Cost (£/tonne Product)
Ammonium Nitrate 34.5% £138 £207 £276 £345 £414 £483
Urea a 46.0% £184 £276 £368 £460 £552 £644
Urea-Ammonium Nitrate Liquid a 28.0% £112 £168 £224 £280 £336 £392
n
Cost of Fertiliser Nitrogen £/kg N £0.40 £0.60 £0.80 £1.00 £1.20 £1.40
Change to recommended N for Oilseed Rape (kg N/ha)
Grain sale price (£/tonne) 200 20 -20 -50 -70 -80 -100
  225 30 -10 -30 -60 -70 -90
  250 40 0 -20 -50 -60 -80
  275 50 10 -10 -40 -50 -70
  300 60 20 -10 -30 -50 -60
  325 70 30 0 -20 -40 -50
  350 70 40 10 -10 -30 -50
  375 80 40 20 -10 -20 -40
  400 90 50 20 0 -20 -30
  425 90 50 30 10 -10 -30
  450 100 60 30 10 -10 -20

a. See notes on efficiency of use of different kinds of applied nitrogen page 48

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