Researcher evaluating multiple approaches to manage resistant weeds
PRINCESS ANNE, Md. — One of the promoted benefits of using cover crops is weed suppression over winter and into spring and with herbicide resistant weeds a constant battle for farmers, researchers continue to study how the crops can best be used to limit resistance.
Dr. Naveen Kumar Dixit, a University of Maryland Eastern Shore researcher, is evaluating multiple approaches to manage resistant weeds — particularly marestail and Palmer amaranth — including single crops and mixes. The cover crop trials include crimson clover, forage radish, oats, rye, and hairy vetch planted last October in separate and mixed blocks over three replications.
Visual observations show impressive early results, with many of the blocks having few marestail weeds amongst the cover crop and those weeds within the blocks are smaller than marestail growing outside them.
Measured in December, Dixit said the blocks had between 100 and 150 weeds each.
“As you enter the blocks you will find some weeds but definitely this is working as you compare to the fallow blocks,” Dixit said, walking around the plots. “We are declining the population. Another thing is decreasing the size of the plant which is very important because larger plants become resistant easier.”
As soybeans are planted, managed and harvested in the plots, Dixit and his team will collect data on energizing weeds’ leaf area and dry matter, the biotypes of herbicide resistant weeds, weed height and population.
“If you have leaf area and dry matter we can calculate a large number of growth parameters,” he said.
They’ll also measure phosphorus uptake, phosphorus content in soil of the blocks and number of pollinators visiting.
Dixit said the research aims to select the best cover crop or crop mix for weed suppression and resistance control.
Marestail can be especially troublesome in no-till systems, Dixit said, as its seed germinates on the soil surface.
Marestail seed does not have a dormancy requirement to germinate, plants can produce more then 200,000 seed and the seed can be spread by wind for miles.
The cover crop replications are one component of a research project studying herbicide resistance in soybean production, funded by the Maryland Soybean Board.
Tillage practices, stacked trait soybean cultivars, multiple spectrum herbicide evaluation are other areas involved in the project, Dixit said and data from each will be collected for forming a comprehensive strategy.
“With ever-evolving herbicide resistance and lack of novel herbicide mode of action, it becomes extremely difficult and expensive to control weed damage on farms,” Dixit wrote in the project’s grant proposal. “We are expecting the development of a cost effective diversified (herbicide resistant) management technology for soybean cultivation in Maryland.”
Walking along the edge of the research blocks, Dixit said better strategies will help farmers on their own operations but to truly conquer herbicide resistant weeds, farmers working in a coordinated fashion to stop the spread will be key.
“A community approach is required, I think,” he said.
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