‘Pay me now or pay me later’ on pre herbicides

Pre-emergence herbicide can be a good investment.

Soybean growers can easily have $100 an acre tied up in their crop before their soybeans even emerge from the ground thanks to rising costs for seed, equipment, diesel and burndown and pre-emergence herbicides.

But that money, particularly for pre-emergence herbicides, can be a good investment based on what ag distributors and retailers are predicting about the price and availability of glyphosate, dicamba and glufosinate postemergence products in 2022.

“One of the first comments I get back about these pre-emergence treatments is, well, that gets to be really expensive, right?” said Dr. Tommy Butts, Extension weed scientist with the University of Arkansas System Division of Agriculture. “Eighteen, 20 to $25 an acre for these, and, if we’re doing the Trivents and Zidua, more like $40 an acre.”

Butts, one of the speakers for the virtual Arkansas Rice and Soybean Field Day last fall, was explaining the results of a study involving 20 pre-emergence herbicides at the Jackson County Extension Center near Newport, Ark. Plots in the study received a single application of a pre-emergence product and no postemergence herbicide.

“I understand that’s real expensive, and, again, I’m not recommending you make one herbicide application and walk away,” he said. “But we have really significant control here from one pre-emergence application.”


Earlier in his presentation Butts discussed the SPORTS acronym developed by University of Arkansas weed scientists for the 2022 season. One of the letters stands for Required Integrated Weed Management or the use of cultural practices to help growers augment the herbicide program in their soybeans.

The study at the Jackson County Center also involved planting a single soybean variety in different row spacings with and without pre-emergence herbicides to determine the level of weed control provided.

“So two factors here – the importance of those integrated weed management tactics, such as row spacings, but also the importance of early season weed control to maximize our soybean growth and to maximize weed control throughout the season,” he said.

“Although it can be expensive on the front end using these pre-emergence herbicides, it can save us money on the back end by either eliminating a postemergence application or allowing us to be more timely with our postemergence applications. It can also give more flexibility to spray our second application.”

In his presentation, Butts stood in a plot in which soybeans were planted in 30-inch rows with a pre-emergence herbicide application.

Pre-emergence program

“You'll notice the soybeans have grown quite well; they.re getting close to my waist, and they've nearly canopied,” he said. “With the pre-emergence program the soil is still really clean even where the crop hasn't completely canopied.

“The early season weed control is a big benefit, even though we're on 30-inch row spacings, which we consider to be a little bit wider row spacing. We're still being clean, and we're almost at canopy to shade out that ground and make sure that we don't have any other seeds germinate from sunlight hitting the ground.”

Butts moved to another trial that was planted in 30-inch rows but did not receive a pre-emergence herbicide application to control weeds that emerged with the soybeans. The difference was striking.

“You'll notice our soybeans have been hindered in their growth,” he said. “They're only just a little bit over knee high on me. You can see we're much farther from canopy closure with these beans. We had that early season competition compared to our previous trial where we had those pre-emergence herbicides.

“Those soybeans were able to grow uninhibited, put on a lot more growth and canopied quicker than these. And you’ll notice we have a lot more weed escapes here. We relied solely on those postemergence products, and we ended up with less weed control than we did over there where we were able to use those pre-emergence herbicides.

To view the presentation, visit Weed Control in Soybean: Pre-Emergence Trials, Early-Season Control (uada.edu).

TAGS: Herbicide
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