EDMONTON – Winter annuals are forget-me-nots.
This weed type has been ignored with the move to crops seeded directly into stubble. Most producers do a simple spring burnoff ahead of the seed drill and the problem is solved.
Or is it?
Plant researcher Ken Sapsford of the University of Saskatchewan found that winter annuals need to be controlled early. He told producers attending last month’s Farm Tech Conference in Edmonton they shouldn’t turn their backs on winter annual weeds because it will cost them money.
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As prairie producers expand their annual seeded acreage, the goal of seeding every crop early has become impossible. Often weed control is staged to take place a few days ahead of seeding.
” ‘I’ll just wait for that next flush of weeds’ is often what producers say to themselves,” said Sapsford.
Tom Jensen, director of the International Plant Nutrition Institute in Saskatoon, told producers attending the Saskatchewan Soil Conservation Association meeting in Regina last month that early seeding in wheat and most other crops is critical to maximizing yield. He said plants need to maximize their access to nutrients and moisture early in the growing season.
Sapsford’s research has shown that while early seeding is beneficial to yield, early spraying is far more important.
From six years of data the researcher concluded that with a few exceptions, producers could count on an average eight percent increase in spring wheat yield by applying their spring burn-off herbicide in the first week of May.
The trials included three scenarios: glyphosate applied in the first week of May, seeded to spring wheat three days later; glyphosate applied in the first week of May and seeded in the last week of the month; and glyphosate applied in the last week of May and seeded three days after that burn-off application.
“It didn’t matter when it was applied, the glyphosate did a great job. We got 90 percent or better (weed control of the winter annuals),” he said.
Spring moisture wasn’t an issue either.
The researchers found that whether it was dry or moist, the yields improved depending on when the weeds were controlled.
“We had lots of moisture in May and June in most of our sites. We have had 191 percent of our usual moisture in 2005 in some sites. In 2006, we had 152 (percent), 141 (percent) in 2007. There was plenty of moisture available, we thought,” he said.
Winter annuals consume large quantities of moisture if given the opportunity, say researchers.
The most common winter annuals, flixweed, narrow leafed hawk’s beard, stinkweed, shepherd’s purse and in some areas winter annual cleavers, appear to have a greater effect on yield than previously thought.
Whether there is another effect created by the presence of the weeds hasn’t been fully studied, but the application strategy of early spring burnoff proved to be more valuable than seeding date.
Early sprayed, early seeded spring wheat in the trials yielded 37.5 bushels per acre, while early sprayed, late seeded crops averaged 37 bu. and late sprayed, late seeded just 34.7 bu.
Canadian western red spring wheat is predicted to bring about $10.50 per bu. for the 2008-09 crop year. Based on Sapsford’s research, producers who do their spring burnoff early and seed later in the month would improve their gross returns by an average of $24.15 per acre over waiting to spray until just before late season seeding.
“For that kind of return you could easily afford to go back out and hit the wild oats with a second burnoff if you had to,” he said.
Sapsford said producers should count on their in-crop herbicide applications to take care of later flushes of weeds.
