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P and K recommendations

Apply phosphorous and potassium fertilisers in late February/ early March to ensure optimum spring growth in crops. Only apply N when soil and weather conditions are suitable for example soil temperatures are >5.5 degrees C, soils have a positive soil moisture deficit SMD (good trafficability) and forecasted improving weather conditions.

Table 3: P & K requirements for oilseed rape yielding 5 t/ha

Soil index

P kg/ha (units/ac)

K kg/ha (units/ac)


55 (44)

105 (84)


45 (36)

90 (72)


35 (28)

75 (60)





Nitrogen and Sulphur application

Only start the fertiliser N programme when soils and weather conditions are suitable to avoid the loss of N to the environment.  Always use an ammonium based fertiliser N for the first split to reduce N losses to either air or water.

N Recommended rates vary from 225-140 kg/ha at index 1-4 respectively. 

OSR is responsive to Sulphur at 30- 35 kg/ha. Ensure S is in first nitrogen split.

Table 2: Suggested Nitrogen Strategy for optimum canopy management (target 5.0 t/ha yielding crop)

Crop Description

(total N)

Early Split

(Late Feb)

Main split

(Mid March)

Seed fill

(Late March/Early April)

GAI <1.0 (225 kg/ha)

70 kg/ha  (Late Feb)

120 kg/ha

35 kg/ha

GAI 1.0 (210 kg/ha)

50 kg/ha (Early March)

100 kg/ha

60 kg/ha

GAI 1.5 (190 kg/ha)

40 kg/ha (Early March)

90 kg/ha

60 kg/ha

GAI 2.0 (130 kg/ha)


70 kg/ha

60 kg/ha

If total N rates allow, add 30 kg/ha N for a target yield of 5.0 t/ha – check your whole farm Nutrient Management Plan

An excel calculator is available to calculate the nitrogen requirement for oilseed rape based on the GAI of the crop (You may need to download google sheets onto your phone to use the calculator).

GreenBookOilseedRape (48KB, PDF Format)

Canopy Management (PDF)

OSR N Calculator (Excel)