In both winter and spring wheat, early weed control minimizes yield losses. The impact of weed infestations on yield depends on whether the weeds emerge prior to the crop, at the same time as the crop, or after the crop has already emerged and is more competitive.
Sometimes winter wheat producers forget that a strategy used to control weeds early in spring wheat should also be developed to protect yield in winter wheat.
Dr. Phil Stahlman, research weed scientist with Kansas State University Agricultural Research Center at Hays, says, “Anything a grower can do to give the winter wheat crop an advantage over the weeds will pay off,” he says.
“The winter wheat grower wants to get the crop up and out of the ground and growing rapidly. Giving that crop a three-week head start over any weed development means you’ve won quite a bit of the battle.”
Stahlman says the research data is consistent. “Data indicates that weeds that emerge within two to three weeks of the time the crop emerges are the most competitive,” he explains. “Weeds that emerge three weeks or later after the crop, in particular spring weed emergence, are going to be much less competitive than weeds that emerge simultaneously with the crop.”
In essence, the weed-free period is the minimum length of time that a crop should be weed-free or very close to weed-free in order to avoid a yield or quality reduction.
“For spring wheat, the critical weed-free period is the one-to three-leaf stage of development,” explains Pamela de Rocquigny, provincial cereal specialist with Manitoba Agriculture, Food and Rural Initiatives in Carman. However, the critical weed-free period can vary by the year and the field. It is affected by factors such as weather conditions, moisture, soils, weed species, weed density and crop competitiveness.”
When weeds emerge at the same time as a spring wheat crop, they should be controlled at the one- to three-leaf stage of the crop. “The optimal timing will depend on weeds present, the stage of the weeds, the stage of the crop and the herbicide used,” says de Rocquigny. “Fields with uneven emergence or variability in the field can impact the timing of spraying the crop.”
“Read herbicide product labels carefully,” de Rocquigny advises. They outline the recommended crop and weed stage for optimal control of weeds. Selection and timing in the various herbicide products vary in optimal crop and weed growth staging for control.
It makes sense that an early herbicide application to control weeds will benefit the crop and help it get ahead of the weeds by reducing competition for moisture and nutrients.
“Growers need to be aware that larger weeds are more difficult to control,” says Stahlman. “So by waiting to control weeds, not only will you end up with a larger weed that may be more difficult to control, you will have already allowed quite a bit of the weed’s interference with the crop to take place.”
Stahlman says the critical weed-free period for winter wheat is a complex question and depends a great deal on the level of resources – water, nutrients, growing conditions – and weed density.
Winter wheat yield loss
“For winter wheat growers, having weeds controlled within a month after green-up in the spring is critical,” says Stahlman. “It’s the critical period. Yield loss during that time is not that great; however, previous research shows that each week delay after that time period results in exponential increases of yield loss.”
Removing early weed competition in winter wheat also improves establishment and the ability to survive over the winter. U.S. winter wheat producers in the southern and central Great Plains typically control weeds in the spring. They wait to assess crop conditions until the winter eases up.
“A lot of our growers like to do some top-dressing of nitrogen in the spring and prefer to couple that with the herbicide application,” says Stahlman. “However, if growers have to wait for better timing for the fertilizer application, they may have waited too long for the best herbicide application timing.”
Employ all the strategies
“Herbicides are one strategy for early weed control in spring and winter wheat crops,” says de Rocquigny. “Other important integrated weed management strategies include field scouting, crop rotations, crop type and field selection.”
She adds: “For both spring and winter wheat crops, it is well known that the earlier the producer can get in the field and apply herbicides, the better the control. Make it your priority to do anything you can do, to give your crop the advantage, particularly in the critical weed-free period. Otherwise, the weeds compete for available light, nutrients and moisture, reducing yield potential and net returns.”
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In both winter and spring wheat, early weed control minimizes yield losses. The impact of weed infestations on yield depends on whether the weeds emerge prior to the crop, at the same time as the crop, or after the crop has already emerged and is more competitive.
Sometimes winter wheat producers forget that a strategy used to control weeds early in spring wheat should also be developed to protect yield in winter wheat.
Dr. Phil Stahlman, research weed scientist with Kansas State University Agricultural Research Center at Hays, says, “Anything a grower can do to give the winter wheat crop an advantage over the weeds will pay off,” he says.
“The winter wheat grower wants to get the crop up and out of the ground and growing rapidly. Giving that crop a three-week head start over any weed development means you’ve won quite a bit of the battle.”
Stahlman says the research data is consistent. “Data indicates that weeds that emerge within two to three weeks of the time the crop emerges are the most competitive,” he explains. “Weeds that emerge three weeks or later after the crop, in particular spring weed emergence, are going to be much less competitive than weeds that emerge simultaneously with the crop.”
In essence, the weed-free period is the minimum length of time that a crop should be weed-free or very close to weed-free in order to avoid a yield or quality reduction.
“For spring wheat, the critical weed-free period is the one-to three-leaf stage of development,” explains Pamela de Rocquigny, provincial cereal specialist with Manitoba Agriculture, Food and Rural Initiatives in Carman. However, the critical weed-free period can vary by the year and the field. It is affected by factors such as weather conditions, moisture, soils, weed species, weed density and crop competitiveness.”
When weeds emerge at the same time as a spring wheat crop, they should be controlled at the one- to three-leaf stage of the crop. “The optimal timing will depend on weeds present, the stage of the weeds, the stage of the crop and the herbicide used,” says de Rocquigny. “Fields with uneven emergence or variability in the field can impact the timing of spraying the crop.”
“Read herbicide product labels carefully,” de Rocquigny advises. They outline the recommended crop and weed stage for optimal control of weeds. Selection and timing in the various herbicide products vary in optimal crop and weed growth staging for control.
It makes sense that an early herbicide application to control weeds will benefit the crop and help it get ahead of the weeds by reducing competition for moisture and nutrients.
“Growers need to be aware that larger weeds are more difficult to control,” says Stahlman. “So by waiting to control weeds, not only will you end up with a larger weed that may be more difficult to control, you will have already allowed quite a bit of the weed’s interference with the crop to take place.”
Stahlman says the critical weed-free period for winter wheat is a complex question and depends a great deal on the level of resources – water, nutrients, growing conditions – and weed density.
Winter wheat yield loss
“For winter wheat growers, having weeds controlled within a month after green-up in the spring is critical,” says Stahlman. “It’s the critical period. Yield loss during that time is not that great; however, previous research shows that each week delay after that time period results in exponential increases of yield loss.”
Removing early weed competition in winter wheat also improves establishment and the ability to survive over the winter. U.S. winter wheat producers in the southern and central Great Plains typically control weeds in the spring. They wait to assess crop conditions until the winter eases up.
“A lot of our growers like to do some top-dressing of nitrogen in the spring and prefer to couple that with the herbicide application,” says Stahlman. “However, if growers have to wait for better timing for the fertilizer application, they may have waited too long for the best herbicide application timing.”
Employ all the strategies
“Herbicides are one strategy for early weed control in spring and winter wheat crops,” says de Rocquigny. “Other important integrated weed management strategies include field scouting, crop rotations, crop type and field selection.”
She adds: “For both spring and winter wheat crops, it is well known that the earlier the producer can get in the field and apply herbicides, the better the control. Make it your priority to do anything you can do, to give your crop the advantage, particularly in the critical weed-free period. Otherwise, the weeds compete for available light, nutrients and moisture, reducing yield potential and net returns.”
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Reply #1 on : Fri July 09, 2010, 06:16:47
Posts: 1
Reply #1 on : Fri July 09, 2010, 06:16:47