Yield, yield formation, and blackleg disease of oilseed rape cultivated in high-intensity crop rotations

ABSTRACT

The short-term economic benefit has in recent years prompted farmers to grow oilseed rape (OSR) (Brassica napus L.) and thus the frequency of this crop increased in German crop rotations. Here, we investigate the impact of high-intensity OSR crop rotations on yield, yield formation, and blackleg disease (Leptosphaeria maculans) in a rotation experiment in the Hercynian dry region of Central Germany over two seasons (2014/2015 – 2015/2016). The preceding crop combinations compared were winter wheat (WW) (Triticum aestivum L.)-WW, WW-OSR, OSR-OSR, and an OSR monoculture. Furthermore, the fertilizer treatments 120 kg N ha⁻¹ and 180 kg N ha⁻¹ were analyzed.

Higher OSR cropping intensity decreased seed yields, however, with a variation among years and oil yield was highest when OSR was following WW-WW over both years. Minor differences were observed among the yield components, but significantly less pods per m² were developed in a long-term OSR monoculture. The disease assessment clearly showed an increased blackleg incidence and severity when OSR was grown successively.

Results of our study emphasize that high-intensity OSR production will very likely be unsustainable over the long term associated with yield losses and increased infestation levels of blackleg disease.

KEYWORDS:

• Brassica napus L.
• crop rotation
• yield components
• Leptosphaeria maculans
• nitrogen fertilization

Acknowledgments

We gratefully thank Martina Fuhrmann, Helge-Stephan Pentschew, Bernd Look, Reinhard Just, Marion Herrfurth, Kerstin Lausch, Florian Hickmann and Elisabeth Rittweger for their dedicated technical assistance.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The project was funded by the Federal Ministry of Food and Agriculture by decision of the German Bundestag and via the Fachagentur Nachwachsende Rohstoffe e. V. within the joint project ‘Mitigation of greenhouse gas emissions from rapeseed cultivation’.