“High rates of nitrogen may make weeds more competitive and produce more seed, which can result in spread.”
It’s May and your wheat is off to a great start. You seeded into a clean field and the seedlings are looking healthy and vigorous. A couple of weeks later, a second flush of wild oats starts making an appearance. You’re worried about your yield taking a hit and start considering your options.
When a second flush of wild oats came up in Todd Borstmayer’s wheat crop, he says he wasn’t surprised. “There were a lot of wild oats in the field where we did the pre-seed burndown,” says
Borstmayer, who farms at Cudworth, Saskatchewan. “And conditions last spring were very moist which helped the weed seeds start germinating.” Provincial Weed Control Specialist Clark Brenzil with Saskatchewan Agriculture and Food in Regina says, “Annual weeds tend to have a large initial flush early in the season, but can be followed by an ongoing emergence of plants later in the spring as long as conditions are favourable.
“Warm soils tend to slow down the germination activity in cool-season weeds like wild oats and wild mustard so that a relatively small proportion of remaining seeds germinate and emerge throughout the remainder of the year. Once soils cool again in the fall there can be another flush of these weeds again.”
Brenzil adds that warm-season weeds like green foxtail and redroot pigweed will require much warmer soils before they will begin to germinate. “Freezing cold over winter is a major breaking signal for dormancy in annual weeds,” says Brenzil. “If the conditions are not right for germination, this initial flush can be delayed, complicating weed control efforts.”
Producers should understand that the most critical weeds to control are those present at the early leaf stages of the crop. Brenzil says: “The later weeds emerge relative to the crop stage, the less impact they have on yield and therefore, the less benefit later herbicide applications will have.”
He adds: “The best way to maximize crop yield is to control the weeds at the early crop stage and have a healthy vigorous crop that closes the canopy over exposed soil quickly. Beyond the four-leaf stage, most of the damage is done and herbicide applications made after this point will not pay for themselves.”
“The later weeds emerge relative to the crop stage, the less impact they have on yield and therefore, the less benefit later herbicide applications will have.”
Borstmayer says, “When we saw the second flush of wild oats coming up we were going to leave the field alone, but our check strip was nothing but wild oats. We just couldn’t risk losing the yield so we went back in with a split application of Everest®, which worked really well.” (See Sidebar)
Weed researcher Kirk Howatt, at North Dakota State University at Fargo, says if wild oats emerge at the same time as the crop and are removed at the three-leaf stage, yield loss in wheat ranges from eight to 15 percent. If the wild oats are left until the five-leaf stage, yield losses rise to 25 to 35 percent. And if delayed until the flag leaf stage, wheat yields are cut by 65 to 75 percent.
Early spring applications of nitrogen can break the dormancy of a greater number of wild oat seeds
Researchers have also found that early spring applications of nitrogen can break the dormancy, which in turn increases wild oat germination. Various researchers have reported that increased N at high weed densities provides little improvement in crop yield but tends to increase weed growth.
The take-away is that high rates of applied nitrogen may make weeds more competitive and produce more seed, which can result in spread. This could prove to be costly for producers in terms of unexpected yield loss.
“We don’t want to lose yield to wild oats and green foxtail, especially with current wheat prices,” says Borstmayer. “We went back in with a split application of Everest to get the second flush, and that saved a whole lot of yield. If we have the same conditions next year, we’ll do the split application of Everest again the same way. It definitely worked.”
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“High rates of nitrogen may make weeds more competitive and produce more seed, which can result in spread.”
It’s May and your wheat is off to a great start. You seeded into a clean field and the seedlings are looking healthy and vigorous. A couple of weeks later, a second flush of wild oats starts making an appearance. You’re worried about your yield taking a hit and start considering your options.
When a second flush of wild oats came up in Todd Borstmayer’s wheat crop, he says he wasn’t surprised. “There were a lot of wild oats in the field where we did the pre-seed burndown,” says
Borstmayer, who farms at Cudworth, Saskatchewan. “And conditions last spring were very moist which helped the weed seeds start germinating.” Provincial Weed Control Specialist Clark Brenzil with Saskatchewan Agriculture and Food in Regina says, “Annual weeds tend to have a large initial flush early in the season, but can be followed by an ongoing emergence of plants later in the spring as long as conditions are favourable.
“Warm soils tend to slow down the germination activity in cool-season weeds like wild oats and wild mustard so that a relatively small proportion of remaining seeds germinate and emerge throughout the remainder of the year. Once soils cool again in the fall there can be another flush of these weeds again.”
Brenzil adds that warm-season weeds like green foxtail and redroot pigweed will require much warmer soils before they will begin to germinate. “Freezing cold over winter is a major breaking signal for dormancy in annual weeds,” says Brenzil. “If the conditions are not right for germination, this initial flush can be delayed, complicating weed control efforts.”
Producers should understand that the most critical weeds to control are those present at the early leaf stages of the crop. Brenzil says: “The later weeds emerge relative to the crop stage, the less impact they have on yield and therefore, the less benefit later herbicide applications will have.”
He adds: “The best way to maximize crop yield is to control the weeds at the early crop stage and have a healthy vigorous crop that closes the canopy over exposed soil quickly. Beyond the four-leaf stage, most of the damage is done and herbicide applications made after this point will not pay for themselves.”
“The later weeds emerge relative to the crop stage, the less impact they have on yield and therefore, the less benefit later herbicide applications will have.”
Borstmayer says, “When we saw the second flush of wild oats coming up we were going to leave the field alone, but our check strip was nothing but wild oats. We just couldn’t risk losing the yield so we went back in with a split application of Everest®, which worked really well.” (See Sidebar)
Weed researcher Kirk Howatt, at North Dakota State University at Fargo, says if wild oats emerge at the same time as the crop and are removed at the three-leaf stage, yield loss in wheat ranges from eight to 15 percent. If the wild oats are left until the five-leaf stage, yield losses rise to 25 to 35 percent. And if delayed until the flag leaf stage, wheat yields are cut by 65 to 75 percent.
Early spring applications of nitrogen can break the dormancy of a greater number of wild oat seeds
Researchers have also found that early spring applications of nitrogen can break the dormancy, which in turn increases wild oat germination. Various researchers have reported that increased N at high weed densities provides little improvement in crop yield but tends to increase weed growth.
The take-away is that high rates of applied nitrogen may make weeds more competitive and produce more seed, which can result in spread. This could prove to be costly for producers in terms of unexpected yield loss.
“We don’t want to lose yield to wild oats and green foxtail, especially with current wheat prices,” says Borstmayer. “We went back in with a split application of Everest to get the second flush, and that saved a whole lot of yield. If we have the same conditions next year, we’ll do the split application of Everest again the same way. It definitely worked.”
Write a comment
- Required fields are marked with *.