. However, in recent years interest has grown in mechanisms that destroy weed seed at crop harvest as another method of weed control.
As herbicide resistant weeds have grown as a threat to crops, conventional farmers have joined organic farmers in seeking alternative methods of weed control. Collaborative efforts, such as GROW (Get Rid of Weeds) Through Integrated Weed Management, in which Davis is active in, are examining a variety of tools to tackle weeds.
Davis has tested the Harrington Seed Destructor, a weed seed destroying device towed behind a combine, developed in Australia. It has been effective in destroying 70 to 80 percent of the weed seeds in the fall and that carries through with weed emergence in the spring, he said. However, early models of the seed destructor were cumbersome and expensive compared to newer products he is also studying.
Deere says it will be offering the SCU (Seed Control Unit) with its S-Series combines starting this fall in North America. Pricing has not yet been released, according to Deere spokesman Eric Hodson.
“It is very relevant to organic systems,” Davis said of the seed destructor.
However, its effectiveness depends on what the weed problem might be.
“For annuals, it is tremendous. For perennials, it has less impact,” he said.
It is not recommended to control a Canadian thistle infestation because that weed also reproduces with its rhizomes, with its seeds just a backup in reproduction. But the seed destructor shines with giant ragweed, foxtail, velvet leaf and waterhemp.
Kevin Bradley, a University of Missouri Extension weed scientist, is his second year of a weed seed destruction study with funding from the Missouri Soybean Merchandising Council. His project is called the Seed Terminator, which also makes weed seed unviable by pulverizing it before it exits the combine. Last year, Bradley and his team studied the WeedZapper, which electrocutes weeds and keeps them from producing seed.
“Any tool that keeps weed seed from returning to the soil is valuable for U.S. farmers. These implements will clearly have a fit in the future and we just need more research and perhaps modification to make them more suitable for our U.S. conditions and weed problems,” he said.
Bradley said he expected “some pretty definitive recommendations about seed destruction technologies” after his second year of research at the end of harvest this year, according to Barbara Baylor’s June blog for ILSoyAdvisor, an Illinois Soybean Association checkoff funded program.
Both Bradley and Davis and their teams are also studying the use of cereal rye as a cover crop to reduce waterhemp emergence.
Cultivation still a key
Meanwhile, farmers continue their long history of mastering cultivation as a weed control method. Organic crop farmers Roger and Mary Knutson and their two sons own about nine different kinds of cultivators, which they use in a well-planned system on their farms in Hardin County in central Iowa.
“We need a lot of tools with the weather we have,” Knutson said in a virtual field day at their farm near Hubbard, Iowa on May 30.
The Knutsons have been perfecting their mechanical weed control system for decades.
“It’s very much an ongoing journey,” said son-in-law Jacob Bolson at the field day organized by the Practical Farmers of Iowa.
A big part of their approach is automation. Precision planting and steering systems are key in getting the crop planted well and guiding cultivation equipment to avoid taking out plants, he said.
Automation with GPS, new or used, is worth the investment, Bolson said, noting that it is important to create a system with a multi-year plan “to avoid getting a fragmented mess.”
Knutson is precise in setting up the planter. He has lines marked on the shop to ensure it is set up correctly. Similar precision follows in setting the cultivator.
“You can spend half a day setting a cultivator sometimes,“ Bolson said
Knutson said they typically make about nine passes of a field over the season, including the rotary hoe five days after the corn is planted. Typically his passes include three pre-plant, planting, rotary hoe, three cultivations and the combine.
“I like to do weed control every seven days, depending on rain,” he said.
Soil health is important to Knudson and he knows that less tillage is favored by some, but he is confident the total system on his organic farm provides good soil health.
Another virtual field day series is planned for September. The Midwest Mechanical Weed Control (MMWC) Field Day, founded by Wisconsin farmer Sam Hitchcock Tilton, is set to hold its fourth annual event. Central Illinois farmer Hans Bishop of PrairiErth Farm will host some of the events on his farm at Atlanta, Ill.
