Cover crops now play an integral role in many farming systems, but with sky-high glyphosate costs, tight application windows and often unfavourable conditions, getting them controlled ahead of the following crop can be a challenge.
With so many different species potentially being grown, controlling them in other crops in the rotation may not be straightforward, says Adam Espir, commercial technical manager at FMC.
Problems “People are having real problems controlling cover crops such as phacelia in following cereal crops. Once you put these cover crops in the rotation, they will become weeds. We really see these as weeds of the future.”
In trials at Bright Seeds’ headquarters in Fovant, Wiltshire, Mr Espir has looked at the use of different herbicides to control volunteer cover crops such as fodder radish, rye, berseem clover, phacelia, vetch and chicory.
In the trials, Centium 360CS (clomazone) at 0.2 litres/hectare was applied pre-em of the cover crops and controlled chicory and vetch, but not radish or kale.
“Centium can be used in spring peas and beans, so this information is useful if volunteers are expected in these spring pulses,” Mr Espir says.
A range of sulfonylurea (SU) herbicides typically used in cereal crops was also trialled on volunteer cover crops four to eight inches tall and results three weeks later showed that all performed well.
“Of the products tested, Ally Max SX performed the best with its tribenuron component adding significantly to the weed control.
“While effective against some cover crops, Jubilee SX and Harmony M did not control some of the species as well as Ally Max SX,” adds Mr Espir.
Despite trials being undertaken during the autumn on a growing cover crop, Mr Espir believes that when the herbicides are applied in the spring onto volunteers in a cereal crop, control is likely to be even stronger.
“In a spring barley crop, for example, volunteers would be sprayed in April or May when the weeds are actively growing, not October when there are declining temperatures.
“Also, with potentially less glyphosate available in spring to spray off over-wintered cover crops, growers may need to rely more on the SUs, so having this information about controlling volunteer cover crops is very important.