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Multi-pronged approach needed to knock out weeds
Mar. 16, 2016
Integrating precision ag technology with long-time weed control practices may allow producers to increase weed control effectiveness.
Kansas State University weed ecology professor Anita Dille, said increased weed resistance to herbicides is forcing producers to rethink weed management strategies in order to suppress the spread of resistant species.
Pre- and post-emergent weed control products have been available for some time. However, combining those tools with precision ag technology could help producers target weed problems at specific sites and slow development of herbicide resistance.
“For many years, weed management was simple. Weeds come up, you spray them and the field is clean,” Dille said. “Now, that approach has stopped working. For an effective weed management strategy, we need to bring back some of our understanding of how weeds are distributed in fields, weed life cycles and signs of resistant patches.”
One new tool producers can use to improve herbicide effectiveness is to identify the variable soil types in each field.
Scientists know some soil-applied herbicide perform differently in different soil types. That means killing weeds may require less herbicide in some areas of the field and more in others.
“Herbicide labels specify rates for coarse, medium and fine soils,” Dille said.
“We know that soils higher in clay require a higher herbicide application rate than other soil types. However, we’re finding that herbicide also responds differently to soil organic matter levels and soil pH. Those conditions are not visible and can vary greatly from field-to-field and farm-to-farm.”
Dille recommends producers looking to revise weed management plans begin with an evaluation of soil variability.
Data, such as soil electrical conductivity (EC) gathered using a Veris MSP3 machine, will identify many soil variables, including water-holding capacity, organic matter, yield potential and soil pH.
The technology has been used since 1996 in more than 40 states and 40 foreign countries.
“Producers could also use historical maps of their fields and convert them into a map that would indicate herbicide rate applications,” she said.
“Variable rate sprayers that could be used to apply herbicide this way are readily accessible through equipment dealers or co-ops. A USDA-funded study is underway in Kansas to confirm that variable rate herbicide application based on soil variability data improves weed control and saves input costs by putting herbicide where it’s most needed at the most effective rate.”
The first step in any effective weed management plan is evaluation of fields to identify weed issues. That information, coupled with soil variability data, will help in selection of the most appropriate herbicide mix for each field.
“Pre- and post-application is a good approach,” Dille said. “It gives you a couple of chances to knock the weeds out. Review herbicide labels thoroughly to see if they provide rate application information for different soil types. It’s possible some fields require only two different rate applications. Using all the available technology to develop a management strategy will provide the best possible results.”
Scouting fields prior to and shortly after herbicide application is necessary for thoroughly treating fields. After application, a weed resistance red flag is living weeds standing among dead weeds of the same species.
“Make sure the weeds were sprayed before they were too big and that the area wasn’t missed when herbicide was applied,” Dille said.
“Weather factors like high winds and rain can cause application issues. If you’ve eliminated all those factors, you’re probably seeing a resistance problem. Diligence in identifying these areas of resistance while they’re still small in an area with few plants will make them much easier to suppress and manage than if you wait until you find several hundred resistant plants.”
Dille also recommends producers consider use of equipment such as cultivators in a localized area where weeds are problematic. The long-used tool could help improve weed control.
“Weeds know how to fill in a gap,” she said.
“Constantly throwing them a curve with different management practices is the best way to keep them off balance. Understanding how precision ag technology can be integrated into a weed management plan will help identify new or different practices that could be implemented.
“There’s a lot of concern with declining commodity prices, and improving weed control could result in improved yield and reduced cost,” Dille added.
“We’re not advocating cutting corners with weed control. Over time, successful weed management should improve overall yield and profitability.”
Source: Missouri Farmer Today
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