Companion cropping to protect oilseed rape

More growers are establishing oilseed rape alongside a companion crop to protect vulnerable young plants.

The first few weeks of rape establishment are probably the most important in the crop’s life, says Lucy Smith-Reeve of Grainseed, who has been researching the impact of growing a companion crop to protect rape early in its establishment.

Rapid establishment

The aim of a companion crop for oilseed rape is to grow something that has rapid establishment and is sensitive to frosts – or chemical application – and either attracts beneficial insects or deters cabbage stem flea neetle.

“In other words, it acts as a sacrificial plant,” says Ms Smith-Reeve. “Species and variety choice in the mix are key to ensure that the companion crop dies back to enable the oilseed rape to reach its full potential. “

Suitable frost-sensitive cover crop mixes which will die back when hit by cold weather include Tabor single cut berseem clover, Lifago buckwheat and fenugreek, adds Ms Smith-Reeves.

Companion crop mixes can be formulated to reduce flea beetle activity by masking the attraction that rape has for the pests and acting as a sacrificial crop. This can include attracting beneficial insects or predators.

Berseem clover and fenugreek both fix nitrogen. The mixes help create more diverse soil microbial activity condition the soil through their extensive rooting systems. They also release nutrients back into the soil.

Pigeons are less likely to graze rape crops when bare soil is covered and landing space is limited. All this helps to improve soil health, soil structure and field drainage.

The downsides of companion cropping include potential extra field work, the extra cost of the companion crop seed and extra chemical application if sowing a mix which isn’t frost sensitive.

But overall the advantages outweigh the disadvantages.