Winter oilseed rape

Last changed: 06 December 2023

Nitrogen management based on precrop and site

Project manager: Maria Stenberg, Department of Soil Sciences, SLU

Project group: Ann-Charlotte Wallenhammar and Ingemar Gruvaeus, The Rural Economy and Agricultural Societies; Lena Engström, Department of Soil Sciences, SLU

The aim of this project is to investigate the possibilities of, and to develop methods, for precrop- and site-adjusted nitrogen application in organic winter rape growing. This will be done in field trials where we investigate the effects of nitrogen levels under varying conditions in order to quantify basic yield, yield potential and nitrogen requirements in relation to soil parameters. We intend to show how nitrogen uptake in winter rape is dependent on nitrogen mineralisation from the soil and to quantify the variation between sites. Factors affecting the amount of nitrogen uptake and soil mineralisation will be identified, documented and quantified. The objective will be to produce decision support data regarding nitrogen fertilisation of winter rape.

The study will consist of eight field trials per year for two years in southern and central Sweden, where nitrogen will be supplied in different amounts and strategies in the form of Vinasse, which has had good effects in the spring on autumn-sown crops.  Various precrops (leys, cereals, peas, green manure leys, field beans)

  • soil texture
  • row spacing and 
  • climate conditions 
  • will be selected.

The trials will be laid out in existing crops in order to ensure a uniform crop stand. Each site will be documented with respect to: 

  • cropping history 
  • soil texture
  • humus content and 
  • other soil parameters. 

The status of the crop stand in all plots will be determined in autumn and at the bud stage by hand-held nitrogen sensors and at each site crop samples will be cut on these occasions. 

  • Root crown diameter, 
  • maximum rooting depth and 
  • incidence of pests and diseases will be monitored. 

The content of mineral nitrogen in the 0-90 cm soil layer will be determined at sowing, in early spring and at harvest. Yield and seed quality, including nitrogen content, will be determined on a plot-wise basis at all sites.


Plant nutrient supply is a key question in organic production of winter oilseed rape (Brassica napus L). The variation in practical cultivation is great and yield levels vary widely, while there is also a lack of knowledge regarding the need for, and profitability of, fertiliser inputs under different conditions, e.g. different precrops.