Mapping black-grass in OSR stubbles


Andrew Ward, Leadenham, Lincolnshire

Oilseed rape is the weak link in our rotation when it comes to black-grass control. The chemical armoury is limited, so achieving a satisfactory kill is difficult.

Surviving black-grass plants are as good as invisible in the crop even when they head, so late-season spot spraying is not feasible.

The crop is so thick that rogueing would be impossible, even if you could see the target.

To limit the consequences, we combine oilseed rape fields with a known black-grass problem after we’ve cleared the clean fields.

We blow out the combine with an airline after each of these fields, to minimise further spread of black-grass seed.

We map every oilseed rape field as we cut it, from the combine cab. All our oilseed rape is desiccated with glyphosate before harvest which results in a tell-tale yellow patch of black-grass leaves in the stubble.

To capture its position, the combine driver notes down the tramline number and distance in from the headland, as displayed on the combine yield monitor. We then upload this information onto our agronomy programme back in the farm office.

We then know exactly which areas of the field to pay particular attention to in the following cereal crop. We can pinpoint how well the chemistry has worked and target other control measures such as rogueing to clear out any survivors, in line with our zero-tolerance black-grass policy.