Decide which weeds you most need to control before cultivating stubbles, a leading agronomist has advised.
Provided the right strategy was adopted and soil moisture retained it was possible to control weeds very well ahead of autumn drilling, said Frontier’s Bob Mills.
“With just enough moisture in the soil surface and an early harvest, most growers will have a great opportunity to seriously deplete weed and volunteer populations in stale seed-beds or stubbles.”
That would help offset the extra weed threat from poor spring control and be especially valuable in countering grassweed resistance, he explained.
After the hot dry summer blackgrass would be especially vulnerable because its seeds should have little dormancy.
Rapid shallow tillage as soon as possible after combining, followed by immediate rolling or pressing, should create ideal stale seed-beds also to deal with other weeds such as sterile and great brome, annual meadow grass, and wild oats as well as volunteer cereals and oilseed rape.
“With soil temperatures as they are, this should stimulate a strong flush of weeds for spraying off within seven to 10 days.”
He recommended a “highly economic” 1.2litres/ha of Roundup Ace (glyphosate) which permitted further cultivation after only six hours.
“You can then till the ground again lightly to produce and spray off a further flush of seedlings comfortably ahead of mid-September drilling.”
But meadow, rye and soft brome species, couch, thistles and volunteer potatoes needed a different approach, stressed Mr Mills.
“These bromes respond to a stale seed-bed but need a period of after-ripening on the surface to encourage good germination.
“So it’s best to leave the stubble undisturbed for three to four weeks before setting it up with cultivation if they are your main problem.
“Equally the worst thing you do with common and onion couch, thistles and volunteer potatoes is to cultivate before spraying off.
“With all these weeds the greatest amount of new growth is what you need. And with couch your problems will only be increased if you chop and spread the rhizomes with a cultivator.”
More time to deal with such weeds was clearly needed, he acknowledged.
“So it would be wise to leave such fields for later autumn-sown crop. Doing so may conflict with your desire to get drilled up as early as possible, but it will invariably pay dividends in avoiding serious crop losses.”ENDS