Field testing new integrated weed management strategies

A Texas A&M AgriLife-led study will research how well several new weed management strategies can help reduce weeds and mitigate the increasing occurrence of herbicide resistance.

The Texas-led $2.23 million grant — Scaling Up Sustainable Integrated Weed Management Solutions to U.S. Field Crop Producers — is funded by the U.S. Department of Agriculture’s Natural Resources Conservation Service through On-Farm Conservation Innovation Trials, a component of the Conservation Innovation Grants program.

“Herbicide resistance in weeds is a serious problem in many agricultural systems throughout the U.S., increasing the cost of weed control and reducing farmer profits,” said Muthukumar Bagavathiannan, Ph.D., Texas A&M AgriLife Research weed scientist in the Department of Soil and Crop Sciences, Bryan-College Station. “We are equally concerned about the negative impacts of weed resistance on conservation agriculture, as producers return to utilizing tillage to manage the resistant weeds.”

Project aims at weeds and conservation

This project, led by Bagavathiannan, includes a network of scientists in the Getting Rid of Weeds, or GROW, alliance, who will focus on integrated weed management, IWM, to address weed resistance. The work has direct implications for protecting and expanding the agricultural land area under conservation practices.

There has been a lot of growth in conservation tillage — minimum till or no-till practices — especially in the Midwest and Northeast. Conservation tillage has also been gradually increasing in the South, he said. But due to herbicide resistance, farmers are reverting back to tillage to control the resistant weeds.

“Tillage for weed resistance management jeopardizes the conservation gains that have been made over several decades,” said Steven Mirsky, Ph.D., a research ecologist at the USDA-Agriculture Research Service Sustainable Agricultural Systems Laboratory, Beltsville, Maryland, who spearheaded the GROW Areawide project on multi-tactic weed resistance management, which provided the foundational knowledge on the IWM tools studied here.

“The project’s focus on implementing non-chemical management tools and being able to prolong the use of available herbicides, thus minimizing the need for farmers to go back to tillage is expected to make tremendous positive impacts on conservation agriculture,” Mirsky said.

Bagavathiannan will be joined on the project by researchers in eight other states in a collaboration with commodity boards, grower networks, and soybean, corn, cotton and wheat producers. The collaborators will work to enhance on-farm adoption of integrated herbicide-resistant weed management with a focus on harvest weed-seed control and cover crops. Precision agriculture and regional expansion of a weed management decision-support tool are other focus areas. The project has received matching funds from DeBruin Engineering of Australia, REDEKOP of Canada, EarthSense Inc. and Cotton Inc.

A new tool in the weed-elimination toolbox

The first effort will be on harvest weed-seed control.

“Weeds that escape the herbicides mature with the crop; during harvest, weed seeds go through the combine and are dispersed throughout the field, contributing to future weed problems,” Bagavathiannan said. “We believe there is an opportunity at harvest to collect these weed seeds and destroy them.”

Different strategies exist to destroy the seed captured by the combine harvester, he said. In this proposal, the team will focus on seed impact mills. The impact mill concept was developed in Australia by a farmer named Ray Harrington to deal with rigid ryegrass seed in wheat. In this approach, the chaff-containing weed seed is separated from straw and is run through an impact mill, which kills weed seeds. Early generation mills were towed behind the combine. The technology has evolved rapidly, and now mills can be directly integrated with combines.

Seed impact mills and other harvest weed-seed control technologies have been broadly adopted by Australian growers. Among the advisors on the project is Michael Walsh, Ph.D., associate professor and director of weed research, University of Sydney. Walsh spent years developing and testing different harvest weed-seed control systems in Australia, including the Harrington Seed Destructor, HSD, and the improved integrated HSD, iHSD.

The team is partnering with DeBruin Engineering, Australia, that manufactures iHSD and REDEKOP, a Canadian manufacturer of seed impact mills. This project is acquiring 16 impact mills to be tested across eight U.S. states.

Walsh said introducing harvest weed-seed control as a new weed control technique into Australian cropping required a substantial and concerted effort, and he expects the same to be required in the U.S.

“This significant grant will enable the required research and development activities that the U.S. cropping industry needs to be able to adopt these systems with confidence,” he said.

Implementing the technology on U.S. soils

The GROW team members have already conducted preliminary studies on the feasibility of harvest weed seed control for the past five years. Preliminary research data indicates the technology is promising.

Bagavathiannan said most existing data on the efficacy of impact mills on U.S. weeds originate from stationary testing and on-station trials, which show greater than 95% destruction of weed seeds, even seeds smaller than those of pigweeds.

“We do need to conduct evaluations on-farm, under realistic production conditions, to demonstrate the potential of this technology, identify areas for further development, and promote farmer adoption,” he said. “This is exactly what this multi-state study is aiming to accomplish.”

The on-farm activities of the project will be conducted on participating farms, ranging in size from 1,000 to 5,000 acres, in three important agricultural regions — North Central, Mid-Atlantic and South Central U.S. Bagavathiannan said the team will integrate cereal rye cover crops with harvest-weed seed control to demonstrate how well these two non-chemical weed management tools can interact with herbicide programs. Field tests in Texas will be in the Upper Gulf Coast area and in the Blacklands region.

The precision agriculture component centers on the development of an image database for important agronomic weeds in the U.S., as well as data flow and cyber infrastructure to facilitate machine learning applications for weed detection and precision management. Drones will be used to assess how IWM practices influence shifts in weed population dynamics and how effectively weed escapes can be spot treated. Field robots will also be utilized for testing ground-level weed detection and actuation systems.

Soil conservation benefits as a result of adopting the IWM solutions will be calculated based on the potential reduction in tillage events that are otherwise required by farmers to manage herbicide-resistant weeds. This reduction will be modeled using WeedRID — a regional IWM decision support tool. The overall conservation benefit calculation will also take into account estimates of how cover crops can reduce herbicide use and decrease weed pressure. The WeedRID model will be parameterized and expanded to include additional weed species, with more regional relevance.

Team members bring diversity to the project

Team members are Adam Davis, Ph.D., University of Illinois; Lauren Lazaro, Ph.D., Louisiana State University AgCenter; Mark VanGessel, Ph.D., University of Delaware; Michael Flessner, Ph.D., and Vijay Singh, Ph.D., Virginia Tech; Prashant Jha, Ph.D., Iowa State University, and Wesley Everman, North Carolina State University, each conducting on-farm experiments in their respective states.

Ankita Raturi, Ph.D., Purdue University, will oversee the development of the web interface and implementation of the WeedRID model. George Frisvold, Ph.D., University of Arizona, is the socio-economist on the project who will coordinate with each region in planning the project research strategy to facilitate tractable economic and social impact analyses.

“Our team has excellent scientists with years of experience in IWM research and has developed close partnerships with equipment companies and commodity support organizations for facilitating IWM adoption in the on-farm trials,” Bagavathiannan said. “We believe this strong partnership will ensure great success of this project.”