Weed control Direct seeding, crop rotations and an early start help farmers to eliminate weeds at the start of the season and net higher yields at the end, says researcher
Seeding early can give producers a good shot at a better yield, but only if a well designed weed control strategy is executed.
The best way to get the crop in early and at the optimal seeding time is to use a combination of integrated weed management (IWM) strategies, says Alberta Agriculture researcher Ross McKenzie, who has decades of research to back his claim.
He said integrated weed management has become good integrated crop management.
“Farmers are doing a much better job of weed control now than they ever have in the past as a result of the IWM options they’ve adopted such as direct seeding, better crop rotations, higher seeding rates, earlier seeding and a range of chemicals to work with to increase economic returns.”
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McKenzie said the key is to eliminate weeds early so that seeding can also be done early. Those two factors together contribute to better quality, better yield and lower risk of crop failure, he added.
Researchers have found that wheat planted at the end of May yields 30 percent less than crops planted at the beginning, and lose one percent per day after the end of April. This is the case even when water isn’t a big issue, such as crops under irrigation.
McKenzie said producers need to use every IWM weapon at their disposal if they want a better chance of seeding in that optimal early window.
Early seeded crops have a yield advantage because they capitalize on early spring moisture and longer spring days, he added.
“If you don’t seed until May 30, then you really only have three weeks before the days start to get shorter,” he said. “The earlier a crop is seeded in that optimum window, the more the crop can take advantage of any early spring precipitation.”
Many of the recommended IWM practices have already been widely adopted, said Rob Dunn, a land management specialist with Alberta Agriculture.
He said producers who want to take full advantage of the early seeding strategy should focus on managing weeds through crop rotations, diversified production systems, increased seeding rates, herbicide-tolerant crops and dealing with fields that are severely infested in advance of seeding.
The key to higher yields and lower costs is to make sure crops can outcompete weeds and late season flushes don’t make seed.
Fall seeded crops and annual forages in the IWM rotation are good ways to deplete the weed seed bank. Winter wheat out-competes most annual weeds and many difficult-to-control weeds such as Canada thistle that emerges late into the spring.
Dunn said farmers can disrupt weeds’ advantages by varying herbicides, crop development timing and crops.
McKenzie said new herbicides that support tillage and continuous cropping have improved farmers’ ability to control tough weeds early.
However, a strategy of seeding first and applying burnoff after emergence can backfire in a year like this one, where it appears seeding might be delayed and if rain comes into the picture.
Dunn said weeds will jump on the crop under those circumstances, even in herbicide tolerant crops such as canola.
“Interference with the crop’s early root development ultimately affects crop vigour and yield,” he said.
A pre-seed burn down with combination products such as glyphosate mixed with florasulam provides control that lasts further into the season in cereal fields heavily infested with weeds or where re-cropping with cereals, canola or peas are planned the following year.
Adding other modes of action to glyphosate also help deal with volunteer herbicide tolerant crops.
