Timing is essential when terminating cover crops, go too soon and limit the amount of biomass accumulation and rooting, whereas leaving it too late on heavy land can lead to problems drilling the subsequent crop.

Nitrogen lock-up is another potential problem that farmers face with the wrong timing. 

When deciding how and when to terminate crops, the key parameters to consider include soil type, cover composition, following crops and machinery availability, says Alice Cannon, Hutchinsons agronomist and regional technical support manager.

Here she shares her learnings on the best approach.

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How do I terminate my catch/intercrop?

“These covers may have been drilled in the early summer and be of good height. Grazing or mowing can be used to manage top growth.

“The majority will contain soft, lush growth with limited height, and termination timing is often driven by soil moisture. Leaving these in the ground for too long can overdry soils.”

She says most drills will be capable of drilling straight into these covers, as the roots anchor the top growth, allowing clean movement through them.

“Try and avoid the temptation to incorporate the cover, this can often make it problematic to drill. Treatment with glyphosate/Kyleo (2,4-D + glyphosate) should occur three to four days before drilling.”

Can I graze my cover?

“Yes, this is a fantastic way to manage the biomass, improve nutrient cycling and inoculate soil with bacteria. It will also reduce the potential N lock-up from high carbon:nitrogen ratio species such as cereals.

However, she warns that farmers need to be wary if there are large quantities of buckwheat in the mix.

Grazing management is vital to success, especially on heavy land, she notes.

“The aim is to graze 60% and trample the remaining cover, promoting exudate and nutrient release. Covers should be mob grazed [high numbers on a small area of land, moved every few days].”

Lighter land is more forgiving and will allow a more relaxed approach if that is preferred, she says.

When should I terminate my cover?

“Clay-based soils are wetter, so moisture management is critical.” They should, therefore, be terminated by the end of November.

She explains that it allows the moisture that will have been drawn around the root ball to dissipate back through the soil while sun and wind dry the surface.

“Leaving the cover over winter will encourage water to be drawn to the surface, meaning the working zone will be wet when it comes to drilling and the drill may struggle to cover the slot.”

Light soils are less problematic and can be terminated at any time, so long as following crop issues have been addressed.

How does my following crop affect termination?

This depends on the cover type, she says.

“Some broad-leaved covers (radish and phacelia) have a tolerance to glyphosate and, therefore, need the use of Kyleo for complete control.

“However, if you are following a broad-leaved cover with a cereal crop, you can finish off the broad-leaved covers in the following cereal.”

Remember that where farmer used cereal covers preceding cereal commercial crops, they will need 40 days to elapse between termination and sowing of a following cereal crop due to allelopathy.

Therefore, Miss Cannon never recommends using cereal covers, especially preceding spring cereal crops.

“Where the cover is ploughed down, this is obviously less of an issue, but arguably negates the value of the cover. However, this may be needed where following crops cannot cope with the residue (such as sugar beet/potatoes). 

Can I drill on the green?

“Quite possibly. You do not always need a new strip or direct drill to drill into a cover.”

She says that the success of direct drilling is down to biomass management and, therefore, will be down to initial species choice.

White mustard, for example, produces long woody stems after winter that degrade very slowly and, therefore, wrap around tines. Legume-based covers, however, are usually much easier for most machines to handle.

“It is always worth trying your drill dry to see how it performs.”

Do crimp rollers work?

“Crimping is ideal for protecting soils against moisture loss, erosion, and weeds, but relies on hard frosts to be an effective alternative to glyphosate – which seemingly we very seldom get,” says Miss Cannon.