A fields recent weed status does not tell enough to ensure sustained control of the problem weed, says Agriis head of agronomy Colin Lloyd.

As many people have been finding to their cost, fields relatively free of black-grass for three or more years can still leap up and bite you if something goes wrong.

In a natural reaction to the very wet winter of 2019, for instance, many fields were sown earlier than advisable last autumn.

Encouraged by this in many cases, the black-grass had an open goal in another wet winter followed by a cold, dry spring which prevented crops getting away as rapidly and competitively as they needed to.

Thankfully, weed populations have generally been lower than usual.

But each plant has tillered much more profusely in more open crops, so seed return this season will be considerable.

Expanded The Stow Longa site near Huntingdon, Cambridgeshire, has expanded from an initial 30 small plots to its current 25 hectares of field-scale investigations.

And 21 years of research at the site, dating back to before the introduction of Atlantis (mesosulfuron + iodosulfuron), have taught Mr Lloyd and his team a lot about managing black-grass.

Foremost learnings to date have been: ■ Pioneering rotational ploughing as a reset in minimal tillage systems.

■ Demonstrating the overriding importance of delayed wheat drilling.

■ Providing industry-recognised ratings for variety competitiveness.

■ Establishing the value of hybrid winter barley for early drilling.

■ Identifying the need to minimise soil movement at drilling.

■ Developing nutritional support tailored to soil and sowing date.

■ Revealing the ineffectiveness of cover crops as a control measure.

■ Showing the imperative of rotational flexibility.

More than anything else, he says, their experience has led them to appreciate that the persistence and adaptability of the weed means a single slip-up can set even the most apparently effective control strategy back several years.