Teagasc tillage specialists have confirmed that on farms where heavy infestations of autumn germinating grass weeds have developed, the only solution may be to get out the plough and start over again.
Min-till cultivation practices can be continued thereafter.
This is a solution that has been recommended on farms where Italian ryegrass, sterile brome and blackgrass issues have arisen.
Teagasc’s Jimmy Staples contributed to the last of the 2021 Enable Conservation Tillage (ECT) webinars. The event was held earlier this week.
He commented: “Continuous cereals grown in tandem with min-till cultivation techniques are predisposed to autumn germinating grass weed problems.
“A specific issue in this regard is the fact that many of these weeds are now resistant to ALS-based herbicides, which are predominantly used with winter wheat crops.
“Unfortunately, these chemistries will not provide the degree of grass weed control that is required when used during the spring months.
“In a number of cases where blackgrass, Italian ryegrass and sterile brome problems have become extremely difficult to manage, the only solution was to plough up those areas of the farms that were most affected.
“Ploughing buries weed seeds to a depth that prevents their germination,” Staples added.
Cost of managing grass weeds
Trying to control highly active, autumn-germinating grass weeds in continuous cereal cropping situations, where no till cultivation has also been used, becomes extremely costly, according to the Teagasc specialist.
He said: “And it can get to the point where switching to the plough is the only feasible cultivation option.”
Where grass weed burdens remain manageable, Staples recommends the use of stale seed beds, and the incorporation of spring crops into the rotations implemented on-farm.
Options here include beans, spring barley and spring oilseed rape.
Blackgrass
Teagasc is specifically recommending a zero tolerance policy, where the control of blackgrass is concerned.
According to Staples, the use of stale seed beds and, if required, multiple cultivations can help to deliver significant levels of grass weed control in cereal crops.
He added: “But the initial cultivation must take place as soon as the straw is lifted from the field. Cultivation must be no deeper than 5cm.
“The seed of grass weeds such a sterile brome need a combination of darkness and a degree of contact with the soil in order to facilitate their germination.
“If sterile brome seeds are allowed to stay on the soil surface, they will tend to go dormant and end up as a major problem in the following crop,” he concluded.