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Back to Bean Basics? | Weed Resistance Prompts Some Farmers To Grow Soybeans the Way They Used To


John Jacobs has always used glyphosate to clean up weed problems on his farm, especially problem fields. But for the most part, he’s never really strayed from a conventional weed-control program for his soybeans. “My basic plan is to plant beans, and use Prowl and Valor in the spring,” he says. “My weed-control program is about $20/acre, but I’m not paying a tech fee.”

Jacobs, from Napoleon, OH, says his weed-management program does take some more time and some additional scouting. “But I like to stay in touch with what my real weed problems are,” Jacobs says. “Just going out and blasting everything with glyphosate would control weeds, but you’d lose track of what weeds you need to control.”

And Jacobs says he continues to look at economic thresholds. “Weeds can cut into yields, but I use guidelines to determine if the control will cost more than the return,” he says. “I look to see if the weed pressure is economically damaging. Even if glyphosate is cheap to spray, that doesn’t always mean it’s giving you a payback.”

Glyphosate remains a very important and effective tool in a weed-management program. And with more than 90% of today’s soybeans planted with the Roundup Ready trait, its popularity shows that glyphosate is still the odds-on choice for weed control in beans. But the appearance of glyphosate-resistant weed biotypes has exploded in recent years, and more and more producers are adding a pre-emergence and/or postemergence herbicide to the mix.

“Glyphosate alone is not recommended,” says Mark Loux, Extension weed scientist at Ohio State University. “While it still offers a control, we stress the need for additional herbicides in the mix.”

Bob Streit, owner of Central Iowa Agronomics in Boone, IA, says: “Over 12 years, we have selected for weeds that are tolerant or resistant to glyphosate. Residual herbicides have been recommended for several years, and now we are seeing different weed-control methods with residuals being used in many herbicide programs.

“And if a producer can get good weed control without needing glyphosate, he can skip the tech fee and put that money into a pre- or postemergence weed-control program,” Steit says.

Evaluating costs

While herbicide rates and costs can vary, a conventional herbicide program using a strong pre- and postemergence program can average from $30 to $45/acre.(attribution coming) And while glyphosate can be cheap (advertised as low as $3/acre), adding a pre-emergence herbicide to a two-pass glyphosate program (which is recommended by weed scientists and chemical companies) can vary depending on the chemical mix – from $10 to $25/acre.

However, a conventional soybean program also means not paying a $15-20/acre tech fee for the soybeans.

“Roundup Ready is still a very important and popular system,” says Brent Neuberger, technical sales manager with FMC. “But there are other herbicide products out there that producers have on hold.”

Whether a Roundup or non-GMO soybean system, it remains important to integrate multiple modes of action in the system. “Not everyone is going back to conventional beans,” Neuberger says. “But producers should look closely at the weeds they need to control and think about a weed-control system, and not just a single-herbicide approach.”

It’s a matter of weighing the costs of the Roundup Ready soybeans and weed control with the current mix of conventional chemistries (and even cultivation) along with conventional soybeans.

“The frequency of acres in which glyphosate alone is sufficient will continue to decline from here on out,” says Aaron Hager, Extension weed scientist at the University of Illinois. “Those days are gone and won’t come back.”

And there are still several chemistries, many with active ingredients that pre-date the development of Roundup Ready soybeans that still work, and work well – with or without glyphosate added to the mix.

A conventional weed-control program can take more planning, since going back and spraying after emergence offers fewer options. But it does help provide early control of weeds before they emerge, and can provide an extra layer of protection if post-season application weather doesn’t cooperate.

Jacobs has grown Roundup Ready soybeans, and notes that in areas with tough weed problems, like Canada thistle, smartweed and common ragweed, he will use a Roundup Ready soybean and go over the top with glyphosate. “But I’ve found that a conventional weed-control program continues to work well.”

And Jacobs says premiums for non-GMO beans are an added benefit.“I’ve tried the Roundup system, and it works well, but I don’t need to pay the technology fee,” Jacobs says. “The icing on the cake is some of the premiums available are truly what helps make my system pay.”

Jacobs says premiums on his non-GMO soybeans run from $1 to $2.25 over the CBOT price, which usually translates to 25-50¢/bu. over local cash markets. He notes that the website gives a rundown on local premiums paid nationwide.

“There’s a little more paperwork involved for some of the premium programs, such as documenting seed source and variety,” Jacobs says. “But it’s not difficult, and the payback is well worth the effort.”


February 2011

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