AMS Boosts Late Weed Control

With planting delays pushing back glyphosate applications, many growers will be treating bigger weeds, which are tougher to control. Water conditioners are a type of herbicide adjuvant that can boost performance, but how do you choose the best one?

Researchers say the ammonium sulfate (AMS) content is key.

Glyphosate and other herbicide labels recommend at least 8.5 pounds (lbs.) of actual ammonium sulfate for every 100 gallons of spray solution. Harder water or more difficult-to-control weeds may require up to 17 lbs. But many premixed water-conditioning adjuvants on the market today deliver less than half the minimum recommended rate.

According to Mark Bernards, weed specialist with University of Nebraska, these adjuvants just don’t have enough AMS to consistently improve weed control. In many cases, performance is no better than glyphosate alone.

In a recent University of Nebraska trial, two out of seven AMS alternatives were as effective as AMS when added to glyphosate for velvetleaf control. The other five resulted in weed control that was equal to — or lower than — weed control from glyphosate alone.

Likewise, the best velvetleaf control in a 2005 Kansas State University study came from glyphosate plus liquid AMS, followed closely by three adjuvants with high AMS content. The remaining six adjuvants had low or no AMS content and resulted in control roughly equal to or less than glyphosate alone.

Bernards says glufosinate has responded similarly to the addition of AMS and low-AMS substitutes.

The take-home seems simple enough: Make sure your herbicide adjuvant contains the minimum recommended rate of AMS. But according to Bernards, few aspects of glyphosate-based weed control systems have generated as much confusion as the role of AMS.

“Shortly after glyphosate was commercialized as Roundup herbicide, farmers and scientists recognized that its ability to kill weeds was reduced when it was mixed with hard water, which was typical for many of the areas where it was being used,” Bernards says.

The problem was antagonism. Negatively charged glyphosate ions bind to positively charged calcium, iron, and magnesium ions — three minerals commonly found in hard water.

“After many years of testing with many different materials, most researchers concluded that AMS was the most consistently effective and economical approach to overcoming hard water antagonism,” says Bernards. If you add enough ammonium sulfate to the spray tank, then the hard water ions (calcium, iron, and magnesium) precipitate from the solution as sulfate salts, and the glyphosate ions bind to the ammonium ions instead of the hard water minerals.

“It’s more commonly used as a nitrogen fertilizer, but all of a sudden ammonium sulfate got a lot of attention for improving weed control,” says Dean Collamer, agronomist with Honeywell. “The hitch was that many granular grades were designed for large-volume fertilizer application — not for dissolving in herbicide spray tanks.”

To alleviate handling problems, suppliers came out with a profusion of AMS pre-mixes made with less AMS and more alternative ingredients, like defoaming agents and surfactants.

“To make sure that you’re using the best adjuvant with your glyphosate spray, ask your supplier for formulations that deliver the minimum required dose of AMS,” advises Bernards. “Alternatively, you can apply a dry sprayable grade of ammonium sulfate directly to your tank.”

Collamer says adjuvant formulators now have access to grades of ammonium sulfate that are free of impurities, easier to dissolve, and more stable in solution. Honeywell, for example, produces Sulf-N PRO soluble ammonium sulfate specifically for liquid applications.

Leave a Reply

Herbicides Stories

Crop InputsEU Glyphosate Controversy Heating Up Yet Again
August 17, 2016
The battle over glyphosate rages on in Europe, creating a lot of question marks over whether the herbicide will continue Read More
Winter Wheat
HerbicidesNew Wheat Herbicide Helps Growers Manage Resistant Weeds
August 2, 2016
Quelex herbicide from Dow AgroSciences is now registered by the U.S. EPA, providing wheat growers a new solution for advanced Read More
Palmer pigweed seedhead in cotton
HerbicidesStudy: Fall Weed Controls Can Make Significant Impact On Glyphosate-Resistant Palmer Amaranth
July 28, 2016
An article published in the latest issue of the journal Weed Science shows that adopting harvest-time and post-harvest weed controls Read More
Palmer pigweed in soybean stubble
HerbicidesSpecial Issue Of Weed Science Explores Human Aspects Of Herbicide Resistance
July 27, 2016
Weeds that evolve resistance to herbicides are a serious threat to global agricultural production. In this Special Issue of Weed Science, Read More
Trending Articles
Corn Field
Eric SfiligojFacing Ag Industry Challenges
September 26, 2016
At the 2016 annual Mid America CropLife Association (MACA) meeting in September, a pair of crop protection company representatives discussed Read More
Bayer Monsanto
Crop InputsBayer-Monsanto Mega-Merger: 6 Things You Need To Know
September 14, 2016
Mega mergers have become almost routine in the agricultural industry. Right on the heels of Monday’s news that fertilizer giants Potash Read More
Potash Corp Agrium
Crop InputsAgrium, Potash Corp To Merge To Create $36 Billion Company
September 12, 2016
Canada’s Agrium Inc. and Potash Corp of Saskatchewan Inc. have agreed to combine in a deal that would create a Read More
Osage Co-op Elevator Osage, IA Finished Building
OpinionAre We Crazy?
September 8, 2016
At some point in the first few months of my employment here at CropLife® magazine, I started getting curious about Read More
ManagementMAGIE 2016 Highlights and Deere Anti-Trust
September 1, 2016
CropLife Editor Eric Sfiligoj discusses the recent Midwest AG Industries Exposition and the Department of Justice’s objection to John Deere Read More
ASMARK 2016 Retailers Live! Tour - CPS
CropLife 100CPS Acquires Texas Retail Operation
August 23, 2016
Crop Production Services (CPS) has acquired the assets of Larry’s Chemical and Spray, Inc., for an undisclosed amount in an Read More
Latest News
Pat Bowe The Andersons
CropLife 100An Eventful Year For The Andersons
October 1, 2016
On November 2, 2015, Patrick Bowe was formerly appointed the new President/CEO of The Andersons, Inc. He became the first Read More
Engenia soybeans
Special ReportsResistant Weeds Continue To Confound Control Efforts
October 1, 2016
In the annals of weed scientists, 2017 will mark a milestone of sorts. This will be the 60th anniversary of Read More
CHS St. Paul, MN fertilizer terminal
CropLife 100Farmers Union Oil Co. Votes To Join CHS
September 30, 2016
Eligible voting members of Farmers Union Oil Co., a diversified agricultural retailer based out of Oslo, MN, have cast affirmative Read More
EmployeesOABA Program Develops Future Generation Of Agribusiness…
September 29, 2016
The Ohio AgriBusiness Association will select up to 25 promising leaders to participate in a leadership enhancement program early next Read More
ManagementThoughts on CropLife America and the PSM Appeal
September 29, 2016
Editors Paul Schrimpf and Eric Sfiligoj talk about the recent CropLife America annual meeting and the successful appeal of the Read More
Corn Field
Industry NewsMarrone Bio Innovations’ SVP And Chief Sustainability O…
September 29, 2016
Marrone Bio Innovations, Inc., a leading provider of effective and environmentally responsible pest management and plant health products, announced today Read More
Young Corn Field
StewardshipStudy: Ohio Farmers Doing ‘A Good Job Of Managing…
September 27, 2016
Leaders from Ohio’s largest grain farming organizations announced today that Ohio farmers are doing their part in effectively managing phosphorus Read More
Growmark FS Outlet
Industry NewsGROWMARK To Purchase Suncor’s Share Of UPI
September 26, 2016
GROWMARK and Suncor have reached an agreement in which GROWMARK will purchase Suncor’s 50% interest in UPI, Inc. in Ontario, Read More
Corn Field
Eric SfiligojFacing Ag Industry Challenges
September 26, 2016
At the 2016 annual Mid America CropLife Association (MACA) meeting in September, a pair of crop protection company representatives discussed Read More
Syngenta Seedcare Institute
Seed/BiotechSyngenta Opens New North America Seedcare Institute In …
September 23, 2016
Syngenta unveiled its new Seedcare Institute in Stanton, MN, during a recent grand opening celebration. More than 150 industry leaders, Read More
StewardshipMonsanto Invests $1.6 Million In System To Quantify Gre…
September 23, 2016
The USDA – Natural Resources Conservation Service (USDA-NRCS) recently awarded the National Corn Growers Association (NCGA) and its Soil Health Read More
Pipe rack
LegislationCourt Sides With Ag Retailers On PSM
September 23, 2016
The D.C. Court of Appeals has ruled the Occupational Safety and Health Administration violated the Occupational Safety and Health Act when Read More
ManagementPacific Coast Fertilizer Announces Interest In Longview…
September 22, 2016
Pacific Coast Fertilizer LP (PCF) announced at the Cowlitz Economic Development Council board of directors meeting its interest in developing Read More
Young corn plants in soil
UncategorizedCool Planet Raises Additional $9 Million To Commerciali…
September 22, 2016
Cool Planet has announced the first close of a new financing round to commercialize the company’s Cool Terra Engineered Biocarbon Read More
Crop InputsJim Loar Promoted To President And CEO Of Cool Planet
September 22, 2016
In a move that reflects and reinforces the company’s commitment to the agricultural market, the Cool Planet board of directors Read More
BlendersNorth Dakota Coop Debuts Dry Fertilizer Plant
September 22, 2016
North Central Grain Cooperative has begun operations at a new dry fertilizer plant at its Rolla, ND, site. It is Read More
Crop InputsMonsanto, Bayer Officials Defend Proposed $66 Billion M…
September 21, 2016
Top officials for Monsanto and Bayer defended their proposed $66 billion merger before skeptical senators on Tuesday, insisting that the Read More
ManagementUpcoming Shows & Recent Events
September 19, 2016
Editors Paul Schrimpf and Eric Sfiligoj talk about upcoming trade shows and events and review the Mid America CropLife Association Read More