Rape absorbs a large amount of nitrogen during autumn which accumulates in the leaves. If the plants loose some leaves during winter, they also loose the nitrogen already accumulated in these leaves. In the early stages of rapeseed development, nitrogen is needed to restore leaf growth, and to develop foliage and pods. In order to determine the amount of nitrogen needed at the beginning of vegetation, the condition of the crop after wintering should be assessed taking into account certain factors such as:
• sowing date
• sowing density
• crop stage before winter
• plant density after wintering
• And plant condition after wintering
A rapeseed yield of 4t/ha absorbs a total of 280kg N/ha. If 80kg N/ha is provided from the soil, then another 200kg N/ha would need to be added as fertilizer.
A stock of 30 plants/m², with 12 leaves and a root neck diameter of 15mm, absorbed already 100-130kg N/ha in autumn, while plants with eight leaves and 10mm root neck thicknesses absorbed about 40-50kg N/ha at the same stock density. Therefore, underdeveloped stocks, need 80-100kg N/ha for the first nitrogen fertilization while well-developed stocks should receive 50-70kg N/ha as a starting dose.
We recommend to use N fertilizers containing directly available nitrates.