Stacking residual herbicides is a key new plank in a Lincolnshire grower’s never-ending struggle to overcome blackgrass this autumn.

The strategy, which will see both Crystal and Avadex applied in sequence, is designed to reduce reliance on Atlantis later in the season.

But Daniel King says attention to detail at every stage of his plan, as well as choosing the right chemicals, will be key to achieving successful grass weed control.

The right cultivations to prepare a good, firm seed-bed, higher seed rates, later drilling dates and the correct nozzle choice are all essential factors.

Mr King, who has a wheat / wheat/rape rotation, is changing strategy this autumn because of a gradual increase in Atlantis resistance on his farm.

After several years of achieving almost full control of blackgrass with Atlantis, performance dropped to 45% control in 2008.

And last year, Atlantis performance dipped so sharply that on one field there was virtually no control.

“The wheat in that field had to be cut for silage,” he laments. “The Atlantis didn’t touch it.”

Over the past two years, BASF has been conducting trials on his farm in Bourne, Lincolnshire, using different combinations of herbicides to try to find him, and growers in similar predicaments, an alternative solution.

The trials have examined how to best optimise the performance of residual herbicides, examining programmes based on combinations of flufenacet, pendimethalin, picolinfen, diflufenican and tri-allate for blackgrass control.

BASF agronomy manager Stewart Woodhead says the best results were achieved from using Avadex followed by Crystal and diflufenican. This combination offers around 90% control of blackgrass.

Crystal used alone as a pre-emergence spray gave nearly 60% control, while adding CTU, prosulfocarb or diflufenican increased control to no more than 70%.

“It’s adding the Avadex to the Crystal programme that really made the difference,” says Mr Woodhead.

Similar results were recorded in independent trials conducted by NIAB TAG.

The results were enough to persuade Mr King to use Avadex, Crystal and DFF across all his crops this autumn.

A contractor will spread the Avadex, a granule which can only be applied by specialist machinery, at £30-£35/ha, within 24 hours of drilling. He will then follow up with a pre-emergence spray of Crystal + diflufenican, regardless of whether soil conditions are dry.

Using Avadex is expensive, he admits, but it is cost-effective compared with the unwelcome prospect of losing large amounts of yield, as much as 4t/ha of wheat in previous years.

The plan is only to spray his crops post-emergence with Atlantis as a last resort if he is not getting enough control.

“I am hoping that I won’t have to go back with any Atlantis, but I need to get blackgrass control in the mid to high 90s to be able to do that,” he says. “But if I need to go back, I will. It is not a question of cost.”

Some growers who relied on Atlantis last year struggled, he notes.

“They will have to decide if the cold, dry weather was to blame and whether they want to carry on using it.”

Equally important for the strategy to be successful will be Mr King’s use of cultural controls.

All the land destined for first wheat, Oakley, has already been cultivated about 10 inches deep with a Vaderstad Topdown.

He has tried ploughing but finds it difficult on heavy land and the blackgrass just returns to the top of the soil after a clean year. He then uses a cultapress to try to achieve a good, firm seed-bed to prepare for drilling.

The drilling will be delayed until 1 October, as late as possible to give the blackgrass more time to grow, before being sprayed off with glyphosate pre-drilling. “I am trying to take as much blackgrass out before I put the seed into the ground.”

High seed rates of 400-450 seeds per sq m will be sown of the Oakley, a competitive variety, to out-compete the blackgrass.

The Oakley will first be treated with Epona seed treatment, which Mr Woodhead says has given 5-10% control of blackgrass in trials, as well as helping to control rusts.

His second wheat variety, Cordiale, will be drilled even later, in mid to late October.

After drilling, the ground will be rolled to get a tight seed-bed with no soil clods.

Sarah Mountford-Smith, BASF’s cereal herbicides product manager, says it is important to minimise clods because clusters of blackgrass can sit underneath them.

“If you spray with a fine droplet, you are not going to make contact with the part of the soil where blackgrass plants are germinating from.”

Application technique is also crucial to Mr King. He will use a Defy nozzle for pre-emergence spraying, with a boom height of 50cm, and the sprayer travelling at 14k/ph.

He likes the Defy nozzle because its alternating forwards and backwards nozzles apply even coverage to both sides of clods where blackgrass resides.

Mr Woodhead is confident that Mr King’s new, rigorous approach to tackling blackgrass will succeed. “Blackgrass resistance is really on the increase. You have to optimise the seed-bed and all the cultivations and manage that together with all the different products available and treat it.”

Using a “fire brigade” strategy with Atlantis to wipe out blackgrass in the spring no longer works for Mr King, and many others, he notes.

“A lot of people have relied on Atlantis for their blackgrass control but it is now suffering from enhanced metabolism resistance as well,” he explains.

“We particularly saw that this year in the four sites we did. With blackgrass you have really got to use all the tools in the armoury.”