Autumn fertilisation in oilseed rape
Precisely coordinated fertilisation is essential to maximise the yield and vitality of oilseed rape. The amount, type and timing of fertilisation must be precisely tailored to the needs of the plants. In winter oilseed rape cultivation, there are two crucial periods for nutrient supply: autumn and the growth period from spring to flowering. This article focuses on the crucial phase of autumn fertilisation.
Importance of autumn fertilisation
Oilseed rape already has a high nutrient requirement in autumn and absorbs around a third of the nutrients it needs. Well-planned autumn fertilisation can help ensure that the plants have an optimal start to the winter and are well prepared for the spring. By making efficient use of nutrients from organic fertilisers, oilseed rape can largely avoid economic and ecological problems caused by nutrient losses.
Nitrogen fertilisation in autumn
The fertilisation of oilseed rape is largely dependent on the availability of nitrogen. For optimum development, oilseed rape absorbs between 180 and 300 kg N/ha in total, of which it removes around 40 to 80 kg N/ha from the soil in autumn. Under optimal growing conditions and weather conditions, nitrogen fertilisation in autumn is often not necessary due to sufficient soil reserves and natural mineralisation, especially with early sowings or previous crops that supply nitrogen. In these cases, the oilseed rape has enough time to absorb the available nutrients from the soil and utilise them optimally before winter sets in. Additional nitrogen fertilisation in such cases could lead to an oversupply, which increases the risk of overgrowth and could impair the winter hardiness of the plants. Nevertheless, there are several reasons that speak in favour of nitrogen fertilisation in late summer in oilseed rape cultivation.
Organic fertiliser in late summer/autumn
Oilseed rape is highly efficient in the use of organic fertilisers. After a cereal preceding crop, nitrogen can be added in late summer (30 – 40 kg N/ha) using organic fertilisers such as liquid manure or farmyard manure. In addition to nitrogen, this can also provide important nutrients such as phosphorus and potassium. Under favourable conditions, additional fertilisation with nitrogen in the form of liquid manure can also be applied in spring. A sensible strategy is to ensure a basic supply of organic fertilisers. The remaining nutrient requirements can then be covered with mineral fertilisers in the spring.