Short season compresses weed battle

The later spring means early seeding isn’t part of effective weed control, so farmers will have to adopt other strategies

It’s finally rubber-boot season on the Prairies, but spring’s tardiness already means the planting season will be tight for some farmers.

Weeds also have some catching up to do and they will come on strong when the heat arrives.

“What I do expect will happen in many places in Western Canada this year is a compressed emergence period for many of the weed species that would normally be emerging throughout the first start of the growing season,” said Charles Geddes, weed expert at Agriculture Canada.

It’s still too early to tell if the rest of spring will promote cooler or warmer season weeds. Either way, it’s likely some crops will struggle to get a competitive advantage by getting a jump on weeds.

“Usually we try to advocate seeding as early as possible to promote a competitive crop, which will help with weed management along with herbicides. I think this year just because everything is going to be so rushed because of the late spring, we’re not going to have as much opportunity to go in as early as we would have liked to,” Geddes said.

He said scouting to determine when that weed flush is happening is going to be key to weed management this year.

Some growers wait until a flush of weeds can be cleaned up before planting, but if the spring continues to run late, many fields will be planted regardless of the state of weed emergence.

Clark Brenzil, provincial weed specialist at Saskatchewan Agriculture, said growers who forgo their preseason burn-down risk have problems later in the year.

“By the time they come in with their in-crop weed control, there could be weeds that are very large and those large weeds are the ones that provide the most competition to the crop. I think (you) proceed as normal, as you would in a regular year, and make sure you use sound weed control practices,” Brenzil said.

Geddes said growers who decide on a pre-emergence herbicide application over a pre-seed burndown risk getting caught by wet weather after seeding.

“Depending on what weather conditions are after seeding, if many of their acres are relying on that pre-emergent rather than a pre-plant and we see quite a bit of rain after seeding, for example, they could be risking the efficacy of their pre-emergence herbicide,” he said.

Growers concerned their early herbicide applications may not be as effective as usual may look to their crop for more help in suppressing weeds.

“Anything we can do to increase the competitive ability of the crop, so increasing seeding rates on crops where that’s a viable option, may be a good idea,” Geddes said.

Brenzil said planning is especially important in years where the seeding season is compressed so growers should look for efficiency in how they do things instead of skipping things.

He said the condensed timeframe may spark a temptation among producers to flail fertilizer on the soil surface rather than band it.

“What you’re doing there is you’re giving the weeds an equal chance to the crop to be able to access that. Often times weeds are better at scrounging the available nutrients than the crop is. By targeting your fertilizer very close to the crop row, and very close to the crop roots, you can focus on fertilizing your crop instead of fertilizing your weeds,” Brenzil said.

Geddes is based in Lethbridge, where overland flooding has many wondering whether waterlogged fields will dry up in time to be planted.

To help suppress weeds, he suggests growers use cover crops instead of just chem-fallow on acres that are too wet to plant this spring.

“If they do run into a situation where they can’t get a crop in because of wet or cold conditions, the best thing would be to plant a cover crop or do something like plant barley and do a barley silage if you’re in an area that has livestock,” Geddes said.

“Anything we can do to have a plant there that’s competing with weeds is going to reduce weed seed production and the potential for selection for herbicide resistance.”

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